Effect of Substrate Bias Voltage on Microstructure and Mechanical Properties of Cr-Nb-Ti-Zr-N-O Ceramic Thin Films Produced by Reactive Sputtering
and Fabio Ferreira 3,4
Round 1
Reviewer 1 Report
The submitted paper deals with the effect of the applied substrate bias voltage on microstructure and mechanical properties of non-equimolar Cr-Nb-Ti-Zr-N-O high entropy ceramic films. Although numerous investigations were conducted in the past by other researchers concerning the bias voltage effects, the submitted work can be characterized as partially innovative, since a different coating system is examined.
Concerning the presented results, my remarks are the following¨
1. Ιt was expected that the hardness of the coating will increase as bias voltage gets higher as it happens with the elasticity modulus. Please explain the presented results.
2. Based on the results shown in figure 7, it is evident that the substrate-coatings adhesion significantly deteriorates at the lowest bias voltage case. Moreover, according to the shown impact imprints in figure 7, the best adhesin appears in the case of the highest bias voltage. The authors have to comment this issue on their work .
Author Response
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Reviewer 2 Report
In this paper, the authors describe the effect of the substrate displacement stress on the microstructure and mechanical properties of non-equimolar Cr-Nb-Ti-Zr-N-O ceramic films of high entropy obtained by the method of reactive sputtering. The research presented in this paper is aimed at improving the mechanical characteristics of wear-resistant coatings Cr-Nb-Ti-Zr-N-O.
Nevertheless, there are several comments to the work:
1) I think that the authors need to describe in more detail the GI-XRD diffractograms of thin films. The authors describe the peaks of Cr-N, Cr-O and Nb-O, but do not pay special attention to other substances contained in the studied samples of Cr-Nb-Zr-Ti-N-O films.
2) I think that the design of the 1st figure should be changed. The values look too small compared to the axis names. Also, on the Y axis, make the values numeric, not exponential.
3) Figure 2 looks unnecessarily deformed; it should be made on a normal scale without distortion.
4) It is worth reducing the SEM of the image shown in Figure 3, or shifting the ruler, since it is cropped in the figures on the right.
5) The quality of the SEM images shown in Figure 7 should be improved.
6) Change the design of the 8th schedule. I think it should be done in the same style as Figures 1 and 2.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
ID: coatings-2437896-peer-review-v1
The authors present the results of the deposition of multi-element ceramic films by means of reactive sputtering. The structural and mechanical properties of Cr-Nb-Ti-Zr-N thin films are investigated by varying the substrate bias. Chemical analysis shows that these non-equimolar thin films have a high amount of oxygen and are composed of amorphous and nano-crystalline nanocomposite phase structures. FESEM and AFM determined that the intermediate level of the substrate bias voltage can produce a uniform surface with a minimum defect density (15%). A maximum hardness, toughness, and wear resistance of H at 24.5 GPa and H/E at 0.107 are reported from the mechanical property analysis. In my opinion, the manuscript is an interesting and relevant topic. However, the manuscript is non-organized, the abstract, the experimental results have several drawbacks. Finally, I suggest that this article should not be accepted as presented. Therefore, I suggest that the following major revisions be considered for acceptance.
1.- The abstract must contain possible applications and trends found as a result of your analysis.
2.- The Introduction, the authors write: “Multi-component coatings are highly used in various fields such as gas sensing and especially machining industries to protect metallic tools. Furthermore, to have better performance in machining (e.g. die machining and cutting tools applications), ceramic thin films are preferred rather than metallic ones [1-4]. It is due to the high hardness, thermal stability, chemical inertness and low thermal coefficient of ceramic materials [5-7].” The general reference list seems a bit thin, considering the evolution in the field within the recent years. To give the readers a much broader view, the potential application of Multi-component coatings photoelectronic devices, such as: Solid State Phenomena (Volume 286), 40-48, https://doi.org/10.4028/www.scientific.net/SSP.286.40; Journal of Alloys and Compounds Volume 726, 5 December 2017, Pages 201-208, https://doi.org/10.1016/j.jallcom.2017.07.261; Solid State Phenomena (Volume 286), 33-39, https://doi.org/10.4028/www.scientific.net/SSP.286.33; J Mater Sci 53, 1646–1657 (2018). https://doi.org/10.1007/s10853-017-1602-8; Solar Energy, Volume 173, October 2018, Pages 1025-1031, https://doi.org/10.1016/j.solener.2018.08.058, etc. should be added, so that the readers can be clear about the state-of-the-art of this topic.
In: “Multi-element thin films can be produced in medium (if the system has four elements) and high (if the system has more than four elements) entropy forms. However, it is extremely important to develop the coatings in defectless and nanostructure form to present the best performance [23-26]. Usually, reactive sputtering is a beneficial process to gain high-quality coatings. To control and design the microstructure of thin films, one can alter substrate temperature [27, 28], reactive gas type or content [29, 30], substrate bias voltage [31-33] and target power [34, 35]. Further, it is important to investigate the effect of these parameters on mechanical properties. To add to it, the optimum conditions and properties should be obtained.”
Advances in Mechanical Engineering. 2014;6. doi:10.1155/2014/373847
Vacuum, Volume 84, Issue 10, 19 May 2010, Pages 1187-1190, https://doi.org/10.1016/j.vacuum.2009.10.022
Revista Mexicana de Física , Vol. 63 No. 6 Nov-Dec (2017), https://rmf.smf.mx/ojs/index.php/rmf/article/view/382.
Advances in Mechanical Engineering. 2014;6. doi:10.1155/2014/945819
AIMS Materials Science 2016, Volume 3, Issue 2: 434-447. doi: 10.3934/matersci.2016.2.434
 Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology. 2021;235(6):1190-1202. doi:10.1177/1350650120940071
Materials Letters, Volume 220, 1 June 2018, Pages 156-160, https://doi.org/10.1016/j.matlet.2018.03.036
3.- The author can consider to emphasize the high entropy in this ceramic material, for instance, in [22] mensionated that Cr-Zr-Nb-N composed is a medium entropy alloy. It can be explained.
4.- From the results of the X-ray pattern: the authors analized the evolution of the peaks of CrO2, NbN, CrO2, Cr2N, Nb2N, CrO2, CrN and Nb2N corresponding to with the variation of the substrate vias voltage and energy. Can you explain what is happening with titanium?
5.- In the text the characteristics of SEM equipment used in this work is lost. Please insert it.
6.- Improve Figure 2; homogenize unit cm-1 (lines 128 – 129)
7.- In the SEM analysis, the authors describe macro-particles and micro-voids as the major defects. What is the relationship between defects and voids?
8.- To carry out the fracture study, the authors subject the thin films to 500mN. Why that load specifically? with a lower load the surface will not fracture?
9.- Concerning the high density of defects, the authors can mention, if these are interstitial; vacances; or dislocating? How affect the bias voltage and amount of the precursor
10.- Finally, let us see how these films are used?
Minor editing of English language required
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Τhe submitted paper can be accepted for publication in the current form.
Reviewer 3 Report
The authors have clarified and improved the presentation of the writing. In my opinion, the article can be accepted in its present form.
