Multi-Process and Interdisciplinary Approaches in Modern Coating and Surface Design

Thermomechanical action during high-performance diamond grinding of sintered cutting Al₂O₃/TiC and SiAlON ceramics leads to increased defectiveness of the surface layer of the deposited TiZrN and CrAlSiN/DLC coatings. It predetermines the discontinuous and porous coatings and reduces its effectiveness under abrasive exposure and fretting wear. The developed technological approach is based on “dry” etching with beams of accelerated argon atoms with an energy of 5 keV for high-performance removal of defects. It ensures the removal of the defective layer on ceramics and reduces the index of defectiveness (the product of defects’ density per unit surface area) by several orders of magnitude, compared with diamond grinding. There are no pronounced discontinuities and pores in the microstructure of coatings. Under mechanical loads, the coatings ensure a stable boundary anti-friction film between the ceramics and counter body that significantly increases the wear resistance of samples. The treatment reduces the volumetric wear under 20 min of abrasive action by 2 and 6 times for TiZrN and CrAlSiN/DLC coatings for Al₂O₃/TiC and by 5 and 23 times for SiAlON. The volumetric wear under fretting wear at 105 friction cycles is reduced by 2–3 times for both coatings for Al₂O₃/TiC and by 3–4 times for SiAlON. Full article

The aim of this experiment was to determine the effect of the addition of strontium oxide on the recrystallization of zirconium silicate when adding strontium oxide to the glaze composition. Zirconia glazes (four different contents) were prepared, to which strontium oxide was added in amounts of 0, 1, 3, 6, and 12 mass% SrO. The characteristic temperatures of the raw glazes were measured, based on which the maximum firing temperatures were determined. The fired glazes were subjected to a study of their phase compositions and an observation of their microstructures. An analysis of the characteristic temperatures showed a fluxing effect, but it was not as strong for all glazes. Differences in the amount of the crystalline phase of zirconium silicate obtained in the fired glazes, as well as the partial transition of zirconium silicate to the amorphous phase, were observed. Observations of the microstructure clearly indicated an increase in the homogeneity of the distribution of zirconium silicate. Full article

In recent years, the utilization of microfluidic devices for precise manipulation of small flows has significantly increased. The effective management of microfluidics is closely associated with microchannel fabrication. The fabrication method employed for microfluidic devices directly impacts the roughness of the microchannels, consequently influencing the flows within them. In this study, the surface roughness of microchannels was investigated through three different fabrication processes: PDMS lithography, PLA printing, and UV resin printing. This research compared and analyzed the surface roughness of the microchannels fabricated using these methods. Furthermore, supported by a dynamic fluid simulator, the impact of surface roughness on flow behavior was shown. Results reveal varying degrees of roughness prominence in curved regions. Comparing microfluidic device fabrication techniques is crucial to optimize the process, control roughness, analyze flow rates, and select a proper material to be used in the development of microfluidic devices. Full article

Using a synthetic antifoulant is an alternative technique to using a natural antifoulant for its economical and large-scale production characteristics. In this study, we synthesized allyl 3-oxzo[d]isothiazole-2(3H)-carboxylate (BIT-C) and a series of other heterocyclic compounds, including triazole, pyridine, and thiazole derivatives. These heterocyclic monomers were used to prepare a new series of acrylic polymers by grafting them onto the side chains. The weight change on the 42nd day was less than −0.091 mg/cm⁻², indicating that antifoulants can be released into seawater consistently and enduringly. The antibacterial and anti-algae tests revealed that all the polymers had exceptional inhibition rates on E. coli, S. aureus, Chlorella, and Chaetoceros curvisetus, with the highest inhibition rates of 99.81%, 99.22%, 92.70%, and 95.42%, respectively. Furthermore, the oyster and barnacle density and algae coverage rate were only about 200 per square meter and 10%, compared to 1800 per square meter and 100% of a blank plate after 90 days hanging in a real marine environment, showing a promising antifouling performance. This work verifies the possibility of a method for grafting different heterocycles on a single polymer to make a series of polymers that can be useful as an environmentally friendly antifouling coating. Full article

The main purpose of electromagnetic interference (EMI) shielding coatings is the insulation of sensitive devices and protect people from electromagnetic field exposure due to its effects on the human body. This paper investigates the dielectric properties, and electromagnetic shielding performances of graphite and carbon black (CB) filled epoxy matrix composites produced by the mechanical mixing method. The sample compositions were created at rates ranging from 1 to 7 wt%. Samples were analyzed by Vector Network Analyzer (VNA) using the coaxial method in the range of 1–14 GHz, including L band, S band, C band, X band and partially Ku band. After determining the scattering parameters with VNA, AC conductivity, absorption, reflection and total shielding efficiency values were calculated. At high frequencies, almost all the samples showed higher AC conductivity. CB-filled samples show higher AC conductivity than graphite-filled samples. The total shielding efficiency (SE_T) of the graphite-added samples (19–21 dB) is slightly higher than the carbon black-added samples (8–17 dB). Distinct filling ratios in graphite-added samples result in closer shielding behavior in contrast to carbon black-added samples. However, higher shielding efficiency is observed as the CB filler ratio increases. The shielding efficiencies of the samples with both types of filling materials vary little depending on the frequency. Reflection is the main mechanism of the shielding efficiency, which constitutes the majority of total efficiency for all types of samples. Full article

A crucial factor of a nitriding process of treated parts is surface roughness. Eight samples of 42CrMo4 steel were used to investigate the parameter represented by Ra. In the study, the innovative combined microhardness profiles were used to present results within the compound zone and diffusion layer. Therefore, two loads were applied in the compound zone, 5 gf, and diffusion layer, 500 gf. Observation with SEM and chemical analysis of the investigated samples showed a correlation between microstructure, nitrogen concentration and microhardness of the compound zone. XRD diffraction was used to identify the phase composition. Moreover, the X-ray photoelectron spectroscopy technique was also applied in the study. No distinct correlations between compound zone morphology and the Ra parameter were observed. The thickness value of the structure was constant and fluctuated around 20 µm in the vast majority of the examined cases. However, analysis of the results revealed a dependence between the Ra parameter and diffusion layer thickness. The values of this parameter varied in the range of 356–394 µm depending on the Ra parameter. A distinct nitrided layer was observed on the polished sample. Full article

Currently, most thermal spray coating service providers expect original equipment manufacturers (OEMs) to suggest the coating recipe, comprising of the right coating equipment, starting process parameters, type of inert gases, and robot program. The microstructure and mechanical properties may not comply in the first few runs. Feedback from a competent material testing service provider forms the initial step to adjust the parameters in the development journey, toward identifying the processing parameters required to obtain an acceptable coating. With the surge of interest in sustainable manufacturing, the time spent on trials in the future will shrink, and a more rigorous process needs to be applied to achieve the “right-first-time manufacturing” approach in thermal spraying. However, a framework for the systematic development of thermal spray parameter optimisation is lacking. This article provides a framework, based on a logical acumen, in selecting the right process parameters, using available data and prior knowledge about the thermal spraying process. To that end, the article summarises the extant developmental journey of thermal spray process parameters, by covering the aspects of equipment choice, robot and spray parameters, and how to minimise iterations, using diagnostic tools to get to the end solution most efficiently. This article, in its current form, will serve as a good guide for early career engineers and scientists or workers, to minimise the time processing window, by avoiding endless iterations to deposit a certain type of coating using thermal spraying. Besides, this work is also aimed at transforming academic research innovations to a robust and repeatable industrial manufacturing process. Full article

During the process of laser cladding IN718/WC composite coatings, the dissolution and metallurgical reaction of WC particles significantly influence the microstructures of the coatings. However, the limited experimental methods restrict direct observation and prevent a deep understanding of this complicated process. Therefore, a novel numerical model for the solidification process of IN718/WC composite coatings was proposed. The model was established with the coupled multi-phase-field model and lattice Boltzmann method. Different kinds of microstructure around WC particles were simulated by the model and verified by experiments. Subsequently, microhardness and wear tests were carried out to investigate the improved mechanical properties of IN718 coatings reinforced by WC particles. The results show that the cellular alloy reaction layer, IN718 grains, and eutectic structure are formed, in turn, around WC particles. The convection in the laser molten pool can induce double-tail-like or spindle-like WC convection diffusion bands. The hardness of these bands is higher than that of the IN718 matrix. More importantly, WC convection diffusion bands can inhibit the growth of columnar crystals, because the dissolved WC can decrease the freezing temperature of the melt. Finally, mechanical property tests show that WC particles increase the hardness of the coating and significantly improve its wear resistance. Full article

We present a novel device for generating suspension droplets and studying droplet impact against solid substrates. The proposed droplet generator extends beyond previous designs by introducing hydraulic machinery that includes separate hydraulic and test containers. This eliminates mixing between the test liquid and the hydraulic liquid above the latch that connects the two containers, thus ensuring reliable clogless operation. The device can produce droplets of controllable sizes between 0.75 and 4.4 mm, and droplets can contain suspension particles of 45 μm to 300 μm size. Repeatability tests show that, at constant control parameters, the median relative droplet size deviation from the target value is ±0.9% and the maximum relative deviation is ±9.1%. We also explore different collision scenarios, which we change from spreading to bouncing by varying the substrate wettability. In addition, the shape of the stain and the resulting spatial distribution of particles are found to be sensitive to particle size. Full article