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Lubricants
Volume 11
Issue 5
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Lubricants, Volume 11, Issue 5 (May 2023) – 46 articles

Cover Story (view full-size image): Layered hexagonal boron nitride (h-BN) with good lubricating properties is expected to become one of the top choices for green lubricant additives. However, the poor dispersibility in lubricants and difficulties in preparing spherical particles of h-BN limit its application. Herein, a simple method for preparing spherical h-BN was presented by one-step laser irradiation in liquid at ambient conditions. As PAO6 additives, laser-induced h-BN nanospheres can achieve good dispersion stability and show excellent tribological properties, which are mainly due to the ball bearing, depositional absorption and repair effect of the spherical particles. This simple laser irradiation method provides a new method by which to prepare spherical hexagonal boron nitride lubricating oil additives. View this paper
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14 pages, 5024 KiB  
Article
Thermal–Mechanical Coupling Analysis of Wheel–Rail Sliding Friction under Two-Point Contact Conditions
by Feng Han, Hao Wei and Yang Liu
Lubricants 2023, 11(5), 232; https://doi.org/10.3390/lubricants11050232 - 22 May 2023
Viewed by 1854
Abstract
The generation of wheel–rail-sliding frictional heat is often accompanied by transverse displacement of a wheel. To study the thermal problem of wheel–rail sliding friction at two-point contact, this paper uses an LM tread wheel and a 60 kg·m−1 rail as examples. A [...] Read more.
The generation of wheel–rail-sliding frictional heat is often accompanied by transverse displacement of a wheel. To study the thermal problem of wheel–rail sliding friction at two-point contact, this paper uses an LM tread wheel and a 60 kg·m−1 rail as examples. A thermal–mechanical-coupled finite-element model of equal proportion wheel–rail sliding is established. A direct-coupling method is used to analyze the thermal–mechanical coupling of the wheel–rail interface under sliding contact. This model considers the temperature-dependent material properties and boundary conditions, such as thermal convection and thermal dissipation, in the process of nonstationary frictional-heat conduction. Firstly, the effects of different sliding speeds, axle loads, and contact modes on the temperature and stress fields of the contact area are analyzed. Then, the lubrication and cooling effects of friction modifiers on the rail top and rail gauge angle are compared. The results show that, at a sliding speed of 2 m/s and an axle load of 30 t under a sliding condition of 200 mm, on the top and side of the rail, the temperatures at the contact patch centers are 813 °C and 547.7 °C, respectively. Under different operating conditions, the rail-side temperature is 55–75% of that of the temperature at the rail top, and the rail-side contact and friction stress values are 76–96% of those at the rail top. This indicates that frictional thermal damage on the rail side cannot be ignored. With a lower sliding speed, the thermal response of the two contact patches is closer. The impact of axle load on the frictional temperature and stress on the rail side is more critical than the sliding speed. The optimal lubrication choice is overall lubrication, which can decrease the rail top temperature by 47.2% and frictional stress by 56.2%, as well as decreasing the rail side temperature by 70.3% and frictional stress by 77.4%. Full article
(This article belongs to the Special Issue Wheel and Rail Tribology)
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21 pages, 9491 KiB  
Article
Effect of Structural Flexibility of Wheelset/Track on Rail Wear
by Bingguang Wen, Gongquan Tao, Xuguang Wen, Shenghua Wang and Zefeng Wen
Lubricants 2023, 11(5), 231; https://doi.org/10.3390/lubricants11050231 - 21 May 2023
Viewed by 1457
Abstract
To investigate the influence of the structural deformation of the wheelset and track on rail wear in the longitudinal and lateral directions, a rail wear prediction model is established that can calculate the three-dimensional distribution of rail wear. The difference between the multi-rigid-body [...] Read more.
To investigate the influence of the structural deformation of the wheelset and track on rail wear in the longitudinal and lateral directions, a rail wear prediction model is established that can calculate the three-dimensional distribution of rail wear. The difference between the multi-rigid-body dynamic model and the rigid-flexible coupled dynamic model, which considers the structural flexibility of the wheelset and track, is compared in terms of the three-dimensional distribution of rail wear. The results show that the three-dimensional distributions of rail wear predicted by the two models are relatively similar. There is no obvious difference in the wear band, and the rail wear in the longitudinal direction is almost identical. The cross sections of the worn rail shapes determined by the two models are essentially the same, with a maximum difference of 3.6% in the average value of the wear areas of all cross sections. The track irregularity is the main reason for the uneven distribution of rail wear in the longitudinal direction. The position where the rail wear is more pronounced hardly varies with the evolution of the rail wear. It is recommended to use a multi-rigid-body dynamic model for the prediction of rail wear, which allows both calculation accuracy and efficiency. Full article
(This article belongs to the Special Issue Tribology in Mobility, Volume II)
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12 pages, 3185 KiB  
Article
Further Validation of a Simple Mathematical Description of Wear and Contact Pressure Evolution in Sliding Contacts
by Francesca Di Puccio and Lorenza Mattei
Lubricants 2023, 11(5), 230; https://doi.org/10.3390/lubricants11050230 - 21 May 2023
Viewed by 1006
Abstract
The present study proposes the further validation of a simple mathematical procedure recently proposed by the authors to describe contact and wear evolution in line and point contacts. The procedure assumed that the maximum contact pressure could be determined using Hertz equations and [...] Read more.
The present study proposes the further validation of a simple mathematical procedure recently proposed by the authors to describe contact and wear evolution in line and point contacts. The procedure assumed that the maximum contact pressure could be determined using Hertz equations and a parabolic pressure profile. The contact half-width was obtained using the equilibrium equation and the Archard wear law. Several cases were selected from the literature, reporting experimental data or Finite Element simulations, and the results were compared to those obtained with the proposed approach. This paper confirms the reliability and potentialities of the proposed analytical procedure, which is capable of providing accurate solutions in case of frictional contacts and at the borders of the contact area, where the main discrepancies were found in the previous study. Full article
(This article belongs to the Special Issue Advances in Wear Predictive Models)
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12 pages, 4773 KiB  
Article
Tribological Study on Photocatalysis-Assisted Chemical Mechanical Polishing of SiC
by Hyunseop Lee
Lubricants 2023, 11(5), 229; https://doi.org/10.3390/lubricants11050229 - 18 May 2023
Cited by 6 | Viewed by 1285
Abstract
Silicon carbide (SiC) is widely used as a power semiconductor substrate material, even if it takes a large amount of processing time to secure an appropriate surface as a wafer for devices after chemical mechanical polishing (CMP). Therefore, studies on SiC CMP have [...] Read more.
Silicon carbide (SiC) is widely used as a power semiconductor substrate material, even if it takes a large amount of processing time to secure an appropriate surface as a wafer for devices after chemical mechanical polishing (CMP). Therefore, studies on SiC CMP have focused on shortening the processing time by increasing material removal efficiency. Among the methods of SiC CMP that have been widely studied recently, the photocatalysis-assisted CMP (PCMP) method is known to efficiently increase the material removal rate (MRR) of SiC under UV light and photocatalysts. However, a limited number of comparative studies have been conducted on PCMP from a tribology perspective. In this article, a comparative study was conducted from a tribology perspective on CMP, mixed abrasive slurry CMP (MAS CMP), and PCMP. The experimental results demonstrated that SiC PCMP has higher friction and processing temperature than MAS CMP and general CMP, which may be caused by photocatalytic oxidation and the TiO2 particles used as photocatalysts. Full article
(This article belongs to the Special Issue Selected Papers from the K-TRIB2023)
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22 pages, 9275 KiB  
Article
Efficient Sub-Modeling for Adhesive Wear in Elastic–Plastic Spherical Contacts
by Minsi Li, Guo Xiang and Roman Goltsberg
Lubricants 2023, 11(5), 228; https://doi.org/10.3390/lubricants11050228 - 18 May 2023
Viewed by 1141
Abstract
This paper presents a novel approach for simulating adhesive wear in elastic–plastic spherical contacts using an improved finite element sub-model. Initially, a global model with a coarse mesh identifies the potential wear region under combined normal loading and tangential displacement. Subsequently, a refined [...] Read more.
This paper presents a novel approach for simulating adhesive wear in elastic–plastic spherical contacts using an improved finite element sub-model. Initially, a global model with a coarse mesh identifies the potential wear region under combined normal loading and tangential displacement. Subsequently, a refined mesh sub-model simulates the crack initiation and propagation until the formation of a wear particle. This refined sub-model efficiently handles a wide range of spherical radii and normal loads. An expression is derived relating the dimensionless wear volume and wear rate to the dimensionless normal load, revealing the limited effect of the sphere radius on the wear rate. The effect of the mechanical properties on the wear particle morphology is also analyzed. Full article
(This article belongs to the Special Issue Advances in Contact Mechanics)
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19 pages, 11352 KiB  
Article
Application of Taguchi Technique to Study Tribological Properties of Roller-Burnished 36CrNiMo4 Steel
by Andrzej Dzierwa, Nataliia Stelmakh and Nika Tikanashvili
Lubricants 2023, 11(5), 227; https://doi.org/10.3390/lubricants11050227 - 17 May 2023
Cited by 1 | Viewed by 1062
Abstract
The purpose of this work was to study the effect of roller burnishing process on tribological properties of 36CrNiMo4 steel. The experiments were performed under dry and starved lubrication contact conditions. The influence of selected parameters such as applied load, sliding speed, and [...] Read more.
The purpose of this work was to study the effect of roller burnishing process on tribological properties of 36CrNiMo4 steel. The experiments were performed under dry and starved lubrication contact conditions. The influence of selected parameters such as applied load, sliding speed, and sliding distance on the coefficient of friction and wear volume was investigated. The Taguchi technique was used to estimate the parameters significantly affecting the tribological properties. The levels of tested input factors were as follows: applied load—5, 10, and 15 N, sliding speed—0.24, 0.48, and 0.72 m/s, and sliding distance—160, 282, and 404 m. The results revealed that load was the most dominating factor that affects the wear volume and the coefficient of friction. The influence of other input factors was smaller. Regression analysis was also performed to predict tribological behavior. The results demonstrated good agreement between experimental and predicted results. The worn-out samples were analyzed using SEM to reveal the wear mechanism. Full article
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2 pages, 154 KiB  
Editorial
Friction and Lubrication of Sliding Bearings
by Shih-Chieh Lin
Lubricants 2023, 11(5), 226; https://doi.org/10.3390/lubricants11050226 - 17 May 2023
Cited by 1 | Viewed by 976
Abstract
Bearings are essential components of machines, as they provide the low friction and energy consumption required for motion [...] Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings, Volume II)
19 pages, 10175 KiB  
Article
Characterisation of the Contact between Cross-Country Skis and Snow: A Micro-Scale Study Considering the Ski-Base Texture
by Kalle Kalliorinne, Bo N. J. Persson, Joakim Sandberg, Gustav Hindér, Roland Larsson, Hans-Christer Holmberg and Andreas Almqvist
Lubricants 2023, 11(5), 225; https://doi.org/10.3390/lubricants11050225 - 16 May 2023
Cited by 3 | Viewed by 1830
Abstract
In winter sports, the equipment often comes into contact with snow or ice, and this contact generates a force that resists motion. In some sports, such as cross-country skiing, this resistive force can significantly affect the outcome of a race, as a small [...] Read more.
In winter sports, the equipment often comes into contact with snow or ice, and this contact generates a force that resists motion. In some sports, such as cross-country skiing, this resistive force can significantly affect the outcome of a race, as a small reduction in this force can give an athlete an advantage. Researchers have examined the contact between skis and snow in detail, and to fully understand this friction, the entire ski must be studied at various scales. At the macro scale, the entire geometry of the ski is considered and the apparent contact between the ski and the snow is considered and at the micro-scale the contact between the snow and the ski-base textures. In the present work, a method for characterising the contact between the ski-base texture and virtual snow will be presented. Six different ski-base textures will be considered. Five of them are stone-ground ski bases, and three of them have longitudinal linear textures with a varying number of lines and peak-to-valley heights, and the other two are factory-ground “universal” ski bases. The sixth ski base has been fabricated by a steel-scraping procedure. In general, the results show that a ski base texture with a higher Spk value has less real contact area, and that the mutual differences can be large for surfaces with similar Sa values. The average interfacial separation is, in general, correlated with the Sa value, where a “rougher” surface exhibits a larger average interfacial separation. The results for the reciprocal average interfacial separation, which is related to the Couette type of viscous friction, were in line with the general consensus that a “rougher” texture performs better at high speed than a “smoother” one, and it was found that a texture with high Sa and Spk values resulted in a low reciprocal average interfacial separation and consequently low viscous friction. The reciprocal average interfacial separation was found to increase with increasing real contact area, indicating a correlation between the real area of contact and the Couette part of the viscous friction. Full article
(This article belongs to the Special Issue Multiscale and Modern Solutions in the Simulation of Lubricated Contacts)
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15 pages, 4956 KiB  
Article
Tribological Effects of Metalworking Fluids in Cutting Processes
by Florian Pape, Gerhard Poll, Lars Ellersiek, Berend Denkena and Haichao Liu
Lubricants 2023, 11(5), 224; https://doi.org/10.3390/lubricants11050224 - 16 May 2023
Cited by 1 | Viewed by 1454
Abstract
An understanding of the proper application of metalworking fluids (MWFs) is necessary for their implementation in efficient production processes. In addition, the knowledge of the process-related aspect of chip transport and the macroscopic cooling effect, the characteristics and properties of lubricant film formation, [...] Read more.
An understanding of the proper application of metalworking fluids (MWFs) is necessary for their implementation in efficient production processes. In addition, the knowledge of the process-related aspect of chip transport and the macroscopic cooling effect, the characteristics and properties of lubricant film formation, and the cooling conditions in the secondary shear zone on the chip surface, i.e., in the direct vicinity of the material separation, represent a combined fundamental scientific issue within production engineering. The aim is to transfer methods from the field of tribology of machine elements, which have already led to a considerable gain in knowledge in this discipline, to machining and to couple them with already established approaches to machining. In the case of roller bearings, the contact pressure is in the range as the pressure in the contact zone between the cutting insert and chip. Due to this, established methods might be transferred to the cutting process. In addition to classical pin-on-plate and pin-on-ring friction investigations, film thickness measurements were carried out and compared to machining tests. The coefficient of friction determined in the planing test rig is 0.48 for dry cutting, while it is 0.47 for wet cutting. These two values are much larger than the CoF with MWFs measured on the two tribometers. It is shown that the boundary friction of MWF especially influences the machining process. Thus, additives in MWF might have a high significance in machining. Full article
(This article belongs to the Special Issue Methods of Application of Cutting Fluids in Machining)
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16 pages, 4930 KiB  
Article
Lubrication Condition Monitoring in EHD Line Contacts of Thrust Needle Roller Bearing Using the Electrical Impedance Method
by Taisuke Maruyama, Faidhi Radzi, Tsutomu Sato, Shunsuke Iwase, Masayuki Maeda and Ken Nakano
Lubricants 2023, 11(5), 223; https://doi.org/10.3390/lubricants11050223 - 16 May 2023
Cited by 10 | Viewed by 1911
Abstract
In this study, we developed the electrical impedance method which simultaneously measures the thickness and breakdown ratio of oil films in elastohydrodynamic (EHD) line contacts within thrust needle roller bearings. Initially, we theoretically demonstrated that the oil film thickness and breakdown ratio can [...] Read more.
In this study, we developed the electrical impedance method which simultaneously measures the thickness and breakdown ratio of oil films in elastohydrodynamic (EHD) line contacts within thrust needle roller bearings. Initially, we theoretically demonstrated that the oil film thickness and breakdown ratio can be simultaneously measured using the complex impedance that is produced when an AC voltage is applied to EHD line contacts. To verify the measurement accuracy of the electrical method, we monitored the oil film thickness of a thrust needle roller bearing and compared it with the theoretical value. The results revealed that the oil film thickness was thinner than the theoretical value immediately after starting the test, with the breakdown ratio being greater than 0 (indicating mixed lubrication); however, the breakdown ratio decreased over time, and the oil film thickness nearly matched the theoretical value one hour after starting the test, when it is believed that running-in wear is complete (i.e., breakdown ratio ≈ 0). Furthermore, following the test, after examining the race surface, we confirmed that running-in wear had indeed occurred. These results suggest that the developed method can monitor the lubrication conditions in EHD line contacts, such as those in thrust needle roller bearings, in detail. Full article
(This article belongs to the Special Issue Behavior of Lubricated Bearings in Electric Circuits)
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21 pages, 12714 KiB  
Article
Wear Mechanisms in Press Hardening: An Analysis through Comparison of Tribological Tests and Industrial Tools
by Jaume Pujante, Eduard Garcia-Llamas, Giselle Ramírez, Nuria Cuadrado, Agim Ademaj, Montserrat Vilaseca and Daniel Casellas
Lubricants 2023, 11(5), 222; https://doi.org/10.3390/lubricants11050222 - 16 May 2023
Viewed by 1038
Abstract
Press hardened components have become widespread in the automotive industry in structural and crash-resistant applications, thanks to the combination of the complex shapes and high mechanical properties obtained. However, the press hardening of coated boron steel results in severe adhesive-based wear, with tool [...] Read more.
Press hardened components have become widespread in the automotive industry in structural and crash-resistant applications, thanks to the combination of the complex shapes and high mechanical properties obtained. However, the press hardening of coated boron steel results in severe adhesive-based wear, with tool maintenance being required in as few as 3000 cycles. The current industrial implementation of press hardening is defined to work around this phenomenon. While this aspect has been studied by different authors, most of the literature deals with laboratory-scale tribosimulators, leaving an open question into how this knowledge transfers to macroscopic effects on the industrial process. In this work, wear in press hardening is studied by comparing the results obtained in laboratory conditions with a pilot-scale line, and finally, with wear mechanisms observed on industrial tools. The aim of this study is to consolidate the current knowledge about the micro-mechanisms involved, and to understand to what extent the existing tests reproduce the actual mechanisms observed in the press floor. The results show how material transfer mainly happens as an accumulation of dust compacted into initial defects on the tool surface. Moreover, this mechanism is effectively reproduced in laboratory tribosimulators and pilot environments, showing a similar morphology to wear on industrial tools. The work sheds light on the underlying causes of wear, and its potential mitigation strategies. Full article
(This article belongs to the Special Issue Tribology for Lightweighting)
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11 pages, 7172 KiB  
Article
Accelerated Tribo-Films Formation in Complex Adaptive Surface-Engineered Systems under the Extreme Tribological Conditions of Ultra-High-Performance Machining
by German S. Fox-Rabinovich, Iosif S. Gershman and Jose Luis Endrino
Lubricants 2023, 11(5), 221; https://doi.org/10.3390/lubricants11050221 - 15 May 2023
Cited by 2 | Viewed by 1192
Abstract
This study investigates accelerated physical–chemical processes in a complex adaptive surface-engineered system represented by a nano-multilayer TiAlCrSiYN/TiAlCrN PVD coating under the extreme tribological conditions of ultra-high-performance dry machining of hardened H 13 tool steel. These processes are similar to the different catalyzing phenomena. [...] Read more.
This study investigates accelerated physical–chemical processes in a complex adaptive surface-engineered system represented by a nano-multilayer TiAlCrSiYN/TiAlCrN PVD coating under the extreme tribological conditions of ultra-high-performance dry machining of hardened H 13 tool steel. These processes are similar to the different catalyzing phenomena. Experimental results of tool life vs. wear rate, SEM/TEM data of the worn surfaces, XPS and EDS data of tribo-films formed on the friction surfaces, and chip surface morphology are presented in this study. The corresponding relationships between self-organization, self-organized criticality, and various catalyzing phenomena were evaluated on the basis of the accrued data. A method of enhancing these processes through the variation of machining conditions is also outlined, which resulted in the improvement of coated tool life by 35%. Full article
(This article belongs to the Special Issue Self-Organization during Friction: Do We Know Enough about It?)
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15 pages, 9568 KiB  
Article
The Tribological Performance of Frictional Pair of Gas–Liquid Miscible Backflow Pumping Seal in Oil–Air Environment
by Shicong Li, Haoran Liao, Jun Zhao and Shuangxi Li
Lubricants 2023, 11(5), 220; https://doi.org/10.3390/lubricants11050220 - 14 May 2023
Viewed by 1088
Abstract
The gas–liquid miscible backflow pumping seal (G-LMBPHS) is a non-contact mechanical seal that is suitable for high-speed bearing chambers. However, the tribological properties and wear mechanisms of the frictional pair of G-LMBPHS in an oil–air environment have not yet been comprehensively studied. In [...] Read more.
The gas–liquid miscible backflow pumping seal (G-LMBPHS) is a non-contact mechanical seal that is suitable for high-speed bearing chambers. However, the tribological properties and wear mechanisms of the frictional pair of G-LMBPHS in an oil–air environment have not yet been comprehensively studied. In this study, the tribological properties of six frictional pairs, consisting of three hard materials (18Cr2Ni4WA, Al2O3 coating, and Cr2O3 coating) and two soft materials (metal-impregnated graphite [Metal-IG] and resin-impregnated graphite [Resin-IG]), were analyzed using a disc-on-disc tribometer. An oil–air environment was created using a minimal quantity lubrication (MQL) system and a closed chamber. The results show that the COF of the four frictional pairs consisting of two coatings and two graphites decreases gradually with increasing rotational speed, and the frictional pairs composed of Al2O3 coating and Resin-IG and Cr2O3 coating and Resin-IG have the lowest COF between 0.022 and 0.03. Therefore, the frictional pairs of G-LMBPHS are in a mixed lubrication condition. The lubricant in the oil–air environment is adsorbed and stored in pits on the surface of graphite and coatings, enhancing the hydrodynamic effect of the spiral grooves and reducing the COF by up to 45%. Metal-IG has better wear resistance than Resin-IG, and the frictional pair consisting of Cr2O3 coating and Metal-IG has the lightest wear. This study provides an important basis for the selection of G-LMBPHS frictional pairs in oil–air environments. Full article
(This article belongs to the Special Issue Coatings and Lubrication in Extreme Environments)
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21 pages, 8856 KiB  
Article
Digital Twin-Driven Thermal Error Prediction for CNC Machine Tool Spindle
by Quanbo Lu, Dong Zhu, Meng Wang and Mei Li
Lubricants 2023, 11(5), 219; https://doi.org/10.3390/lubricants11050219 - 14 May 2023
Cited by 3 | Viewed by 1472
Abstract
Traditional methods for predicting thermal error ignore the correlation between physical world data and virtual world data, leading to the low prediction accuracy of thermal errors and affecting the normal processing of the CNC machine tool (CNCMT) spindle. To solve the above problem, [...] Read more.
Traditional methods for predicting thermal error ignore the correlation between physical world data and virtual world data, leading to the low prediction accuracy of thermal errors and affecting the normal processing of the CNC machine tool (CNCMT) spindle. To solve the above problem, we propose a thermal error prediction approach based on digital twins and long short-term memory (DT-LSTM). DT-LSTM combines the high simulation capabilities of DT and the strong data processing capabilities of LSTM. Firstly, we develop a DT system for the thermal characteristics analysis of a spindle. When the DT system is implemented, we can obtain the theoretical value of thermal error. Then, the experimental data is used to train LSTM. The output of LSTM is the actual value of thermal error. Finally, the particle swarm optimization (PSO) algorithm fuses the theoretical values of DT with the actual values of LSTM. The case study demonstrates that DT-LSTM has a higher accuracy than the single method by nearly 11%, which improves the prediction performance and robustness of thermal error. Full article
(This article belongs to the Special Issue Advances in Bearing Lubrication and Thermodynamics 2023)
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20 pages, 4980 KiB  
Article
Theoretical and Numerical Investigation of Reduction of Viscous Friction in Circular and Non-Circular Journal Bearings Using Active Lubrication
by Denis Shutin and Yuri Kazakov
Lubricants 2023, 11(5), 218; https://doi.org/10.3390/lubricants11050218 - 13 May 2023
Cited by 1 | Viewed by 1288
Abstract
Reducing friction losses is one of the most common ways to improve fluid film bearings, whose adjustable design provides additional opportunities to improve their dynamic and tribological properties. Previous studies have shown the possibility of reducing viscous friction in actively lubricated bearings by [...] Read more.
Reducing friction losses is one of the most common ways to improve fluid film bearings, whose adjustable design provides additional opportunities to improve their dynamic and tribological properties. Previous studies have shown the possibility of reducing viscous friction in actively lubricated bearings by adjusting the rotor position. This work provides a theoretical justification for the mechanism of this effect for the cases of purely laminar lubricant flows in journal bearings. The operating modes connected with the transition to turbulent phenomena and the occurrence of Taylor vortices are beyond the scope of this paper. Conditions that ensure the minimization of friction losses in hydrodynamic and hybrid bearings with hydrostatic parts are determined based on the equations describing viscous friction in a fluid film. In non-adjustable plain hydrodynamic bearings, the minimum of friction is achieved with the centered shaft position that is actually unstable due to the resulting forces configuration. In actively lubricated hybrid bearings, a further reduction in viscous friction is possible by combining film thickness and pressure distributions. Recombining them, along with adjustment of the shaft position, allows the optimization of the distribution of shear stresses in the fluid film. As a result, the shear stresses caused by the rotation of the shaft can be partially compensated by the stresses caused by the pressure gradient, reducing the torque-resisting rotation. In addition, additional benefits can be obtained in the minimum friction state by the reduced lubricant flow and power losses to its pumping. A series of numerical calculations for elliptical, 3-, and 4-lobe bearings show that non-circular bores provide additional variability in film thickness distribution and a premise for optimizing the bearing tribological parameters. Four-lobe bearing demonstrated the best ability for reducing viscous friction among the considered designs. The results obtained can be used as a basis for further optimization of the geometry of fluid film bearings of both active and passive designs by reducing power losses due to viscous friction. Full article
(This article belongs to the Special Issue Tribology Problems in Rotating Machinery)
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20 pages, 8933 KiB  
Article
Research on Nonconstant and Discontinuous Pumping Characteristics of the Concrete Pump Truck
by Yafeng Ren, Chunyang Bi, Wenwen Lu, Jinning Zhi, Weifeng Yang, Jie Li and Haiwei Wang
Lubricants 2023, 11(5), 217; https://doi.org/10.3390/lubricants11050217 - 13 May 2023
Viewed by 1125
Abstract
The nonconstant concrete flow due to the alternating pumping of the twin cylinder of the hydraulic pump will cause vibration of concrete pump trucks. Furthermore, the discontinuous pumping of concrete caused by inadequate suction and air doping will exacerbate the vibration. In order [...] Read more.
The nonconstant concrete flow due to the alternating pumping of the twin cylinder of the hydraulic pump will cause vibration of concrete pump trucks. Furthermore, the discontinuous pumping of concrete caused by inadequate suction and air doping will exacerbate the vibration. In order to study the effect of nonconstant and discontinuous pumping of concrete on the dynamic response and vibrational stability of the whole vehicle, multi-fluid pumping models with concrete-lubrication gas for straight and elbow pipes are established, respectively, and the boundary conditions of periodic pumping speed are taken into account to compare the rheological characteristics of concrete and the exciting force on the pipe wall under nonconstant pumping, discontinuous pumping and nonconstant discontinuous pumping conditions. Results show that the pipe pressure and the exciting force vary periodically with the pumping speed under nonconstant pumping conditions, and the peak-to-peak value of the pipe pressure and excitation for discontinuous pumping depend on the volume fraction and distribution state of the gas in the pipe. Full article
(This article belongs to the Special Issue Dynamics of Lubricated Interfaces)
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14 pages, 5700 KiB  
Article
Tribological Behavior of Ti-Coated Diamond/Copper Composite Coating Fabricated via Supersonic Laser Deposition
by Qunli Zhang, Yiyun Chen, Bo Li, Changyi Wang, Lijuan Wu and Jianhua Yao
Lubricants 2023, 11(5), 216; https://doi.org/10.3390/lubricants11050216 - 11 May 2023
Cited by 3 | Viewed by 1338
Abstract
Diamond/copper composite coating is promising for wear-resistant applications, owing to the extreme hardness of the diamond reinforcement. Ti-coated diamond/copper composite coatings with various laser powers were successfully fabricated employing the novel manufacturing technology of supersonic laser deposition (SLD). Ti-coated diamond, which was able [...] Read more.
Diamond/copper composite coating is promising for wear-resistant applications, owing to the extreme hardness of the diamond reinforcement. Ti-coated diamond/copper composite coatings with various laser powers were successfully fabricated employing the novel manufacturing technology of supersonic laser deposition (SLD). Ti-coated diamond, which was able to enhance the wettability between diamond and copper, was prepared at the optimal parameters via salt bath. Nano-spherical titanium carbides were uniformly distributed on the diamond’s surface to generate a favorable interface bonding with a copper matrix though mechanical interlocking and metallurgical bonding during impact. Furthermore, the results showed that the transition layer acted as a buffer, preventing the breakage of the diamond in the coating. SLD can prevent the graphitization of the diamonds in the coating due to its low processing temperature. The coordination of laser and diamond metallization significantly improved the tribological properties of the diamond/copper composite coatings with the SLD technique. The microhardness of the diamond/copper composite coating at a laser power of 1000 W reached about 172.58 HV0.1, which was clearly harder than that of the cold sprayed copper. The wear test illustrated that the diamond/copper composite coating at a laser power of 1000 W exhibited a low friction coefficient of 0.44 and a minimal wear rate of 11.85 μm3·N−1·mm−1. SLD technology shows great potential in the field of preparing wear-resistant hard reinforced phase composite coatings. Full article
(This article belongs to the Special Issue Laser Surface Engineering for Tribology)
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14 pages, 2011 KiB  
Perspective
Microalgae Oil-Based Metal Working Fluids for Sustainable Minimum Quantity Lubrication (MQL) Operations—A Perspective
by Leonardo I. Farfan-Cabrera, Alejandro Rojo-Valerio, Juan de Dios Calderon-Najera, Karina G. Coronado-Apodaca, Hafiz M. N. Iqbal, Roberto Parra-Saldivar, Mariana Franco-Morgado and Alex Elias-Zuñiga
Lubricants 2023, 11(5), 215; https://doi.org/10.3390/lubricants11050215 - 10 May 2023
Cited by 2 | Viewed by 2379
Abstract
This article presents a perspective on the potential use of microalgae oils in the production of metal working fluids (MWFs) used for minimum quantity lubrication (MQL) operations. The generalities of MQL operations and requirements of MWFs, and current advances in the development of [...] Read more.
This article presents a perspective on the potential use of microalgae oils in the production of metal working fluids (MWFs) used for minimum quantity lubrication (MQL) operations. The generalities of MQL operations and requirements of MWFs, and current advances in the development of the most promising microalgae oils with high contents of saturated, monounsaturated, and polyunsaturated fatty acids were reviewed and discussed. The analysis of data, discussions, and conclusions of numerous studies published recently and combined with the experience of the multidisciplinary team of authors strongly suggest that microalgae oils do indeed have great potential as sustainable and eco-friendly base oils for producing semi-synthetic MWFs, soluble oils and straight cutting fluids for MQL operations. Additionally, gaps and challenges focused on the use of agro-industry wastewater in microalgae production, green harvesting and oil extraction methods, and replacement of toxic additives in MWFs by green nanoparticles and biopolymers were identified and highlighted for achieving massive microalgae oil-based MWFs production and truly green machining processes. Full article
(This article belongs to the Special Issue Minimum Quantity Lubrication: Environmental Alternatives in Processing)
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19 pages, 6387 KiB  
Article
Performance Analysis of the C/C Composite Cylindrical Reverse Inter-Shaft Gas Film Seal
by Hua Su, Shuaike Zhao and Xiaofei Yang
Lubricants 2023, 11(5), 214; https://doi.org/10.3390/lubricants11050214 - 09 May 2023
Viewed by 1387
Abstract
The reverse inter-shaft gas film seal is a gas path seal used in the intermediate bearing cavity of an aero-engine, which is challenging to implement due to its special installation and usage conditions. This paper proposes a C/C (Carbon/Carbon) composite cylindrical reverse inter-shaft [...] Read more.
The reverse inter-shaft gas film seal is a gas path seal used in the intermediate bearing cavity of an aero-engine, which is challenging to implement due to its special installation and usage conditions. This paper proposes a C/C (Carbon/Carbon) composite cylindrical reverse inter-shaft seal structure and carries out a performance simulation analysis based on bidirectional fluid–solid coupling technology. The results show that the cylindrical reverse inter-shaft gas film seal with double-layer C/C composite sealing rings with different material mesoscopic parameters can balance seal leakage and friction power consumption and is beneficial to improving the comprehensive performance of the seal. As the mesoscopic parameters of the inner sealing ring material increase in warp and weft density, the sealing leakage rate decreases, and the gas film force and gas friction power consumption all increase. As the pressure difference increases, the sealing leakage rate and gas film force increase. As the rotation speed of the inner and outer rotors increases, the seal leakage rate increases, and the gas film force decreases. A C/C composite sealing ring cylindrical reverse inter-shaft gas film seal has a lower leakage rate and larger gas film force than a graphite sealing ring cylindrical reverse inter-shaft seal, which confers certain performance advantages. The work in this paper can provide a reference for the design of reverse inter-shaft seals. Full article
(This article belongs to the Special Issue State-of-the-Art of Tribology in China)
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13 pages, 3798 KiB  
Article
Microstructure and Wear Resistance of Ti5Si3/Ti3Al Composite Coatings Prepared by Laser Cladding on TA2 Titanium Alloy
by Kaijin Huang and Wanxia Huang
Lubricants 2023, 11(5), 213; https://doi.org/10.3390/lubricants11050213 - 09 May 2023
Cited by 3 | Viewed by 1245
Abstract
In order to improve the wear resistance of titanium alloy, a Ti5Si3/Ti3Al composite coating with improved wear resistance was successfully prepared by laser cladding TA2 titanium alloy using the double-layer presetting method of Ti-63 wt.% Al mixed [...] Read more.
In order to improve the wear resistance of titanium alloy, a Ti5Si3/Ti3Al composite coating with improved wear resistance was successfully prepared by laser cladding TA2 titanium alloy using the double-layer presetting method of Ti-63 wt.% Al mixed powder layer/Si powder layer. The microstructure, phase composition and wear resistance of the coating were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and pin-disk friction and wear method. The results show that the coating is mainly composed of the Ti5Si3 primary phase and Ti5Si3/Ti3Al eutectic structure. The microhardness of the coating is higher than that of the matrix. The average microhardness of the coating is about 668 HV0.1, which is 3.34 times that of the matrix. The coating significantly improves the wear resistance of the TA2 matrix, and the mass wear rate is 1/5.79 of that of the TA2 matrix. The main wear mechanisms of the coating are abrasive wear, adhesive wear and oxidative wear, whereas the main wear mechanisms of the TA2 matrix are adhesive wear and oxidative wear. Full article
(This article belongs to the Special Issue Laser Surface Engineering for Tribology)
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29 pages, 16259 KiB  
Article
Dynamic of a Flexible Rotor-Bearing System Supported by Worn Tilting Journal Bearings Experiencing Rub-Impact
by Ebrahim Tofighi-Niaki and Mir Saeed Safizadeh
Lubricants 2023, 11(5), 212; https://doi.org/10.3390/lubricants11050212 - 08 May 2023
Cited by 3 | Viewed by 1579
Abstract
Wear usually occurs in the loaded part of hydrodynamic bearings and leads to bearing geometry imperfections. This paper investigates the effects of wear-induced geometric imperfections of tilting pad journal bearings (TPJBs) on the dynamic behavior of the system. Furthermore, the effect of wear [...] Read more.
Wear usually occurs in the loaded part of hydrodynamic bearings and leads to bearing geometry imperfections. This paper investigates the effects of wear-induced geometric imperfections of tilting pad journal bearings (TPJBs) on the dynamic behavior of the system. Furthermore, the effect of wear on the journal-bearing rub-induced contact pressure severity is investigated. A novel tribo-dynamic model is proposed for a flexible rotor-worn TPJB which integrates a mixed elastohydrodynamic model with a rotor-worn TPJB thermal and dynamic model to assess the effects of the bearing wear progression on rotor-TPJB behavior. Based on the results, wear changes the temperature distribution of the pads and oil film as well as the dynamic behavior of the system. Dynamic simulations reveal a higher vibration level and contact pressure for the worn TPJBs near the system’s critical speed and service speed. Finally, thermal and dynamic condition indicators are suggested to detect TPJB wear severity at its early stages. Full article
(This article belongs to the Special Issue Tribology Problems in Rotating Machinery)
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24 pages, 4323 KiB  
Article
Exploring the Effectiveness of Isatin–Schiff Base as an Environmentally Friendly Corrosion Inhibitor for Mild Steel in Hydrochloric Acid
by Ahmed A. Al-Amiery, Nadia Betti, Wan Nor Roslam Wan Isahak, Waleed Khalid Al-Azzawi and Wan Mohd Norsani Wan Nik
Lubricants 2023, 11(5), 211; https://doi.org/10.3390/lubricants11050211 - 08 May 2023
Cited by 11 | Viewed by 1778
Abstract
A recent study has shown that Schiff base OHMHI is an effective inhibitor of the corrosion of mild steel in acidic media. The study utilized weight loss measurements and electrochemical techniques, such as EIS and potentiodynamic polarization, to analyze the corrosion inhibition efficiency [...] Read more.
A recent study has shown that Schiff base OHMHI is an effective inhibitor of the corrosion of mild steel in acidic media. The study utilized weight loss measurements and electrochemical techniques, such as EIS and potentiodynamic polarization, to analyze the corrosion inhibition efficiency of OHMHI. The results of the study show that the presence of OHMHI in the corrosive environment significantly reduced the corrosion rate of mild steel and increased its corrosion resistance. The impedance spectra analysis indicated that OHMHI was adsorbed on the surface of mild steel, providing a protective layer. The potentiodynamic polarization study confirmed the protective role of OHMHI by showing an increase in the passive current density of the mild steel in the presence of OHMHI. The inhibitory efficiency of OHMHI was found to be 96.1%, indicating that it is an effective corrosion inhibitor for mild steel. The study also investigated the optimal conditions for the use of OHMHI as a corrosion inhibitor, with a concentration of 0.5 mM and a temperature of 303 K being chosen. The Langmuir adsorption isotherm concept was used to demonstrate the physical and chemical adsorption of OHMHI on the surface of mild steel. Morphological investigations of the uninhibited and inhibited surfaces of the mild steel specimen were examined using scanning electron microscopy (SEM) analysis. Furthermore, computational investigations using density functional theory (DFT) and experimental data were merged to explore the corrosion inhibition efficiency and mechanism of inhibition. Although the results are promising, further studies are needed to determine the long-term effects of OHMHI on mild steel corrosion and to evaluate its effectiveness under different environmental conditions. Overall, the study highlights the potential of OHMHI as an effective corrosion inhibitor for mild steel in acidic media. Full article
(This article belongs to the Special Issue Green Corrosion Inhibitors: Natural and Synthetic Organic Inhibitors)
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10 pages, 2984 KiB  
Article
Potential Lubricating Mechanism of Hyaluronic Acid for a Reduction of Albumin-Mediated Friction in the Artificial Joint System
by Chen-Ying Su, Yi-Fang Lu, Yung-Chang Lu, Chang-Hung Huang and Hsu-Wei Fang
Lubricants 2023, 11(5), 210; https://doi.org/10.3390/lubricants11050210 - 08 May 2023
Viewed by 1445
Abstract
The average lifespan of artificial joints is 15–25 years, but it is still too short for young and active patients. Human synovial albumin is easily adsorbed on the surfaces of artificial joint materials and has increased friction when subjected to conformational changes. Most [...] Read more.
The average lifespan of artificial joints is 15–25 years, but it is still too short for young and active patients. Human synovial albumin is easily adsorbed on the surfaces of artificial joint materials and has increased friction when subjected to conformational changes. Most studies have focused on the interaction between synovial fluid components and artificial joints when protein conformation has not been modified, but not on how to reduce friction and wear caused by denatured proteins. This study aimed to investigate whether hyaluronic acid could provide lubrication for albumin-mediated friction when high friction was caused by the disrupted secondary structure of albumin. Thermally processed human synovial albumin was used as denatured protein while friction testing, measurement of conformation, adsorption, and viscosity analysis were investigated. The results demonstrated that adding fresh hyaluronic acid to thermally processed albumin solution could reduce 50% of the friction coefficient caused by totally disrupted albumin. The viscosity of thermally processed albumin with fresh hyaluronic acid increased 40 times more than denatured albumin alone, and the adsorbed albumin area with fresh hyaluronic acid increased twice. The results showed hyaluronic acid provided lubrication by increasing the viscosity for friction mediated by denatured albumin, and it may provide a potential solution for prolonging the lifespan of artificial joints. Full article
(This article belongs to the Special Issue Synovial Lubricated Joints—Devices and Mechanical Behavior)
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11 pages, 5175 KiB  
Article
Effect of CH4 Flow Rate on the Tribological Behaviors of TiCN Films against Si3N4 Ceramic and Steel Ball
by Yanhong Lyu, Jianyun Zheng, Huilian Sun, Xinrong Deng, Yang Liu and Qiaoyu Zhang
Lubricants 2023, 11(5), 209; https://doi.org/10.3390/lubricants11050209 - 08 May 2023
Cited by 1 | Viewed by 1313
Abstract
Control of the structural, mechanical and tribological properties of TiCN films play an important role in its numerous applications, including the cutting tools, mechanical components, aeronautical and biomedical engineering industries. Direct-current magnetron sputtering (DCMS) system was applied to deposit TiCN films onto n-type [...] Read more.
Control of the structural, mechanical and tribological properties of TiCN films play an important role in its numerous applications, including the cutting tools, mechanical components, aeronautical and biomedical engineering industries. Direct-current magnetron sputtering (DCMS) system was applied to deposit TiCN films onto n-type silicon (100) at room temperature. The Ti-TiN interlayer was used to enhance the adhesive strength between the coating and the substrate. The composition and microstructure of the TiCN films were studied using X-ray photoelectron spectroscopy (XPS) and field-emitted scanning electron microscopy (FESEM). The mechanical properties of the films as a function of methane (CH4) flow ratio were then characterized using nano-indentation measurements. The tribological behavior of TiCN films was investigated by UMT-2MT tribometer against a Si3N4 ceramic and AISI52100 steel ball. After the tribological tests, the wear rate of the films was obtained by the 3D surface profiler and the component content of wear debris was evaluated by energy dispersive X-ray spectroscopy (EDS). The results show that the tribological properties of TiCN films are a function of CH4 flow rates. The film obtained at a 10 sccm CH4 flow rate possesses a minimum average COF value of 0.1964 and reaches 72,000 cycles against a Si3N4 ball over the test duration. Furthermore, the wear rate was only 2.076 × 10−6 mm3/N·m. Furthermore, the TiCN films exhibited longer lifespan against the Si3N4 ball than against the steel ball under the normal load of 1 N, indicating that the TiCN films present better lubricative properties when against low-hardness counterparts than high-hardness counterparts. Full article
(This article belongs to the Topic Advanced Manufacturing and Surface Technology)
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23 pages, 7561 KiB  
Article
A Mixed Lubrication Model of Piston Rings on Cylinder Liner Contacts Considering Temperature-Dependent Shear Thinning and Elastic–Plastic Contact
by Nolan Ryan Chu, Robert L Jackson, Hamed Ghaednia and Arup Gangopadhyay
Lubricants 2023, 11(5), 208; https://doi.org/10.3390/lubricants11050208 - 07 May 2023
Cited by 4 | Viewed by 1879
Abstract
This work develops a numerical methodology for predicting the performance of an automotive piston ring system by considering contact and lubrication mechanics. The rough surface contact mechanics and lubrication occurs on a scale much smaller than the size of the piston rings and [...] Read more.
This work develops a numerical methodology for predicting the performance of an automotive piston ring system by considering contact and lubrication mechanics. The rough surface contact mechanics and lubrication occurs on a scale much smaller than the size of the piston rings and therefore the key aspect of the model is an algorithm that simultaneously solves the multiple mechanisms at different scales. The finite element method will be used to model the mechanical deformations of the piston ring surfaces at large scales. The quasi-steady state model includes heat generation due to solid and viscous friction. This heat generation will then be used to predict the temperature rise and thermal effects in the lubricant and component. A statistical rough surface method that renders asperities as elastic–plastic wavy surfaces predicts the solid contact area. The modified Reynolds equation will be solved to consider the effects of mixed hydrodynamic lubrication while using flow factors formulated for actual piston and ring surfaces. The lubricant viscosity depends both on temperature and shear rate. This will allow for the regimes of boundary, mixed, and full-film lubrication to be considered. The model predicts friction for various loads and speeds that are then compared to experimental measurements. Although the contacts operate mostly in the mixed lubrication regime, the model and experiments show changes in friction with load, speed, and temperature. Full article
(This article belongs to the Special Issue Advances in Contact Mechanics)
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15 pages, 7713 KiB  
Article
Tribological Response of δ-Bi2O3 Coatings Deposited by RF Magnetron Sputtering
by Sandra E. Rodil, Osmary Depablos-Rivera and Juan Carlos Sánchez-López
Lubricants 2023, 11(5), 207; https://doi.org/10.3390/lubricants11050207 - 07 May 2023
Cited by 2 | Viewed by 1202
Abstract
Bismuth oxide (Bi2O3) coatings and composite coatings containing this oxide have been studied due to their potential applications in gas sensing, optoelectronics, photocatalysis, and even tribology. Two parametric models based on chemical features have been proposed with the aim [...] Read more.
Bismuth oxide (Bi2O3) coatings and composite coatings containing this oxide have been studied due to their potential applications in gas sensing, optoelectronics, photocatalysis, and even tribology. Two parametric models based on chemical features have been proposed with the aim of predicting the lubricity response of oxides. However, such models predict contradictory values of the coefficient of friction (COF) for Bi2O3. In this study, we deposited Bi2O3 coatings, via magnetron sputtering, on AISI D2 steel substrates to evaluate the tribological responses of the coatings and determine which parametric model describes them better. Experimentally, only coatings presenting the cubic defective fluorite-like δ-Bi2O3 phase could be evaluated. We performed pin-on-disk tests at room temperature and progressively increasing temperatures up to 300 °C using alumina and steel counter-bodies. Low wear and COFs (0.05 to 0.15) indicated that the δ-phase behaves as a lubricious solid, favoring the validity of one of the models. An alternative explanation is proposed for the low COF of the defective fluorite-like structure since it is well known that it contains 25% of anionic vacancies that can be ordered to form low shear-strength planes, similar to the Magnéli phases. Two challenges for future potential applications were observed: one was the low adhesion strength to the substrate, and the other was the thermal stability of this phase. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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16 pages, 7337 KiB  
Article
Selected Aspects of Lubrication in Die Forging Processes at Elevated Temperatures—A Review
by Marek Hawryluk, Łukasz Dudkiewicz, Jan Marzec, Marcin Rychlik and Roger Tkocz
Lubricants 2023, 11(5), 206; https://doi.org/10.3390/lubricants11050206 - 07 May 2023
Cited by 2 | Viewed by 1707
Abstract
The paper concerns selected aspects of the application of cooling–lubricating agents as well as methods and devices assigned to lubrication in hot die forging processes realized at elevated and high temperatures in the context of their effect on the quality of the forgings [...] Read more.
The paper concerns selected aspects of the application of cooling–lubricating agents as well as methods and devices assigned to lubrication in hot die forging processes realized at elevated and high temperatures in the context of their effect on the quality of the forgings and the durability of the forging instrumentation. An analysis was made of the currently used lubricants and their properties and applications in selected industrial forging processes, and a review was conducted of the presently applied cooling–lubricating systems and devices. The article also presents the authors’ own studies referring to the effect of the application of lubricating and cooling agents, the volume of the lubricant portion, the times and directions of its application, and other factors affecting tribological conditions. It also presents lubricating devices constructed based on the knowledge and experience of the authors. The elaborated systems, introduced into selected forging processes, make it possible to examine the effect of the volume and time-frequency of the applied lubricant dose on the wear of the tools and also to select and ensure the optimal tribological conditions in the process with respect to durability. The obtained research results, which were confirmed in the industrial process, indicate the great potential of implementing such devices also in other forging processes because the proposed solutions ensure greater repeatability and stability of working conditions. This increases the efficiency of production and thus significantly reduces the unit production costs, as a two-fold increase (from 8000 to 16,000 forgings) in tool life has been observed. Full article
(This article belongs to the Special Issue Cooling/Lubrication Methods in Surface Engineering and Machining Applications of Different Materials)
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16 pages, 6107 KiB  
Article
Synthesis, Wear and Corrosion of Novel Electrospark and Electrospark–Electrochemical Hybrid Coatings Based on Carbon Steels
by Iurii Benkovsky, Natalia Tsyntsaru, Serhii Silkin, Vladimir Petrenko, Vidas Pakstas, Henrikas Cesiulis and Alexandr Dikusar
Lubricants 2023, 11(5), 205; https://doi.org/10.3390/lubricants11050205 - 05 May 2023
Cited by 1 | Viewed by 988
Abstract
The electrospark deposition (ESD) technique is a low-heat-input process that has great potential for coating applications and the restoration of damaged high-value parts. Carbon steels are commonly used as a substrate material for ESD coatings. However, we demonstrated that carbon steels could be [...] Read more.
The electrospark deposition (ESD) technique is a low-heat-input process that has great potential for coating applications and the restoration of damaged high-value parts. Carbon steels are commonly used as a substrate material for ESD coatings. However, we demonstrated that carbon steels could be used successfully as the electrode tool for the ESD process. Furthermore, ESD coatings commonly have a high as–deposited roughness. In view of this, in order to reduce the roughness of the ESD coatings, electrodeposition as a tool to alter surface morphology was investigated. Hence, the micro-leveling power of several electrolytes for Ni, Fe-W, Fe, and Cr electrodeposition were evaluated. The maximum leveling effect was detected for Ni electroplated from the Watts electrolyte. Thus, the novel hybrid coatings based on an ESD layer and a subsequent layer of electrodeposited Ni were obtained. ESD layers were obtained by using the following electrode tools as anodes: several types of carbon steels (St20, St30, and St45), alloys T15K6 (WC + TiC + Co), CuNiZn; and NiCr. The morphology and structure of the obtained hybrid coatings with an electrodeposited Ni top-layer was analyzed and compared to ESD coatings from the point of view of their wear and corrosion behavior. The wear rate of the novel ESD coatings based on carbon steels was comparable with coatings obtained using the NiCr electrode tool. Moreover, for all the studied cases, the corrosion resistance of the hybrid coatings was higher than for their ESD counterparts and close to electrolytic chromium. Full article
(This article belongs to the Special Issue Friction and Wear of Coatings/Films)
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12 pages, 5358 KiB  
Article
Tribological Properties of Attapulgite Nanofiber as Lubricant Additive for Electric-Brush Plated Ni Coating
by Feng Nan and Dong Wang
Lubricants 2023, 11(5), 204; https://doi.org/10.3390/lubricants11050204 - 05 May 2023
Viewed by 1064
Abstract
In order to expand the application field of attapulgite in tribology, the tribological properties of attapulgite as a lubricant additive on electric-brush plated Ni coating were investigated using the ball-disc contact mode of a SRV-IV friction and wear tester. The worn surfaces were [...] Read more.
In order to expand the application field of attapulgite in tribology, the tribological properties of attapulgite as a lubricant additive on electric-brush plated Ni coating were investigated using the ball-disc contact mode of a SRV-IV friction and wear tester. The worn surfaces were characterized and analyzed via scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Results indicated that the friction-reducing and antiwear properties of 150 SN lubricating oil on the Ni coating were remarkably improved by an appropriate amount of attapulgite. Tribofilm mainly composed of Ni, NiO, SiO2, Al2O3, graphite, and organic compounds was formed on the worn surface under the action of attapulgite, which was responsible for the reduction of friction and wear. Full article
(This article belongs to the Special Issue Tribology of 2D Nanomaterials)
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27 pages, 13405 KiB  
Article
Research on Lubrication Characteristics of Cage-Free Ball Bearing with Local Functional Slot
by Jingwei Zhang, Yuan Zhang, Yanling Zhao and Wenguang Han
Lubricants 2023, 11(5), 203; https://doi.org/10.3390/lubricants11050203 - 02 May 2023
Viewed by 1373
Abstract
The factors affecting the lubrication effect of a ball bearing without cage and containing a functional slot are analyzed, including the structural parameters of the functional slot, the speed of the rolling element, and the deformation of the contact surface, in order to [...] Read more.
The factors affecting the lubrication effect of a ball bearing without cage and containing a functional slot are analyzed, including the structural parameters of the functional slot, the speed of the rolling element, and the deformation of the contact surface, in order to establish the initial oil volume equation. Based on the multiple mesh method and Matlab programming, the established model is solved by obtaining the distribution rules of oil film pressure, oil film thickness, and oil film flow rate between the rolling element, the conventional raceway, and the functional slot under different speed conditions, and by determining the optimal functional slot depth. Finally, through an experiment performed to verify the lubrication effect of the lubricating oil in the functional slot, the results show that the lubricating oil in the functional slot can have a lubricating effect, and the initial amount of lubricating oil needed increases with an increase in speed. Full article
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