Effects of Different Post-Treatments on Arc Erosion Resistance of Cold-Sprayed AgC Composite Electric Contact
, Yan Liu 1, Yanming Chen 1, Jun Zhang 1, Renzhong Huang 2, Jun Tan 3, Zhenggang Li 1 and Bing Yang 1,4,*
Round 1
Reviewer 1 Report
The material of the article is very interesting, the research carried out correctly, is undoubtedly suitable for industrial applications. It has been shown that the surface topography obtained by laser ablation increases its
hydrophobicity (contact angle 125.50), which largely eliminates moisture when the material is used for external contact. It was also shown that the coating after laser treatment has the best resistance to arc erosion,
the lowest rate of arc erosion and the lowest weight loss in the erosion process - after applying 10000 times of arc erosion compared to other treatments. The research has shown (Fig. 4) that after an 8000-fold arc
erosion, the loss of mass, unfortunately, begins to increase. I was wondering how you can try to improve this parameter. The article presents the laser treatment parameters used in these studies. However, there is no
description of the methodology of selecting parameters and the scanning method. Compressive stresses occur in the surface layer after the use of a cold spray technique to deposit the AgC composite onto the copper
substrate. On the other hand, during the next treatment - annealing in the furnace, the compressive stresses disappear and the surface topography becomes hydrophilic. The laser treatment can introduce both
compressive stresses in the surface layer and obtain the appropriate surface topography. The analysis of the presented material shows that the more peaks of unevenness there are, the more the arc energy is dissipated
and we obtain scattered, small areas of remelting and the loss of mass (craters) is smaller. Hydrophobicity is also better in this case. Why does the loss of mass begin to increase after 8000 times arc erosion? This aspect
has not been analyzed. I would suggest that as the arc erosion increases, the peaks of the roughness become blunted and the arc energy dispersion is smaller, so the craters get bigger and the mass loss increases. Most
likely, after 8000 arc strokes, roughness of 8 µm is completely blunted. Since the thickness of the AgC composite coating is 60 µm, it would be possible to design a surface topography, eg with a roughness of 15-20 µm (as long as the size of the 50 µm graphite granulate would not interfere with) to extend the arc erosion fold to the preferred fold. For this purpose, laser scanning (ablation) by the method of diffraction and interference of laser beams could be proposed. This methodology is very extensively described in the literature
(Rui Vilar-Laser Surface Modification of Biomaterials_ Techniques and Applications-Woodhead Publishing
(2016), Elsevier).The selection of laser treatment parameters (changing not only the scanning speed, but also the power density on the sample surface and the pulse duration) can be obtained using, for example, the Kiefer method of experiment planning. Final conclusion: the article can be published as is (with a slight extension of conclusions, perhaps). On the other hand, if the authors considered my recommendations for further
improvement of the surface of the composite coating as appropriate, and would carry out research in this direction, another work could be created.
Comments for author File: 
Comments.pdf
Author Response
Dear reviewer, please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
The present manuscript investigated the effect of post processing on the arc erosion resistance of AgC composite coating deposited via the cold spray method. The topic is interesting and valuable to publish after the following revision.
- Graphite is considered a lubricant. When the graphite powder is mixed with Ag powder it will not be a homogeneous mixture. Authors need to provide detailed images of the raw materials before coating.
- Which type of cold spray system was used in this process? Please outline details of that.
- How the post-processing parameters were selected? Please elaborate!!
- Detailed experimental procedures need to be added, especially the SEM and XRD analysis.
- I do not see any difference in XRD plots.
- What were the residual stresses in the coating?
- What was the surface roughness of the substrate as it will affect the adhesion of the coating?
- What is the adhesion strength of the coating?
- As this is a composite of AgC, there is supposed to be C as a carbide form. However, I do not see any carbide in the microstructure. Please provide evidence of that.
Thanks!!
Author Response
Dear reviewer, please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The reviewer has no further comments or suggestions. The aim of the paper is clear and well defined. The introduction section presents the state of art sufficiently. Experimental methods and materials were described in details. Results were presented clearly and the main effects of post-treatments on phase structure, morphologies, wettability and arc erosion resistance were discussed appropriately using SEM graphs and charts. Discussion was supported by references. SEM pictures are in high quality/resolution and were professionally presented. The trends are presented clearly. The schematic presented in Figure 6 is much appreciated. There are some minor editing issues which reviewer suggest to correct before publication:
- Please polish the text before the final submission, use past tense.
- Line 77 – Please correct MPa
- Descriptions on Figure 1 and 6 could be in publisher font: palatino linotype
- Line 109 – please use commas
- Please make sure that section 3 is justified.
- Line 126: sometimes hours and sometimes h is used. Please use one in whole text
- Line 216: “Here we give a discussion about …” sounds unprofessional. Please use The discussion about …. were given below/accordingly/etc. Please consider.
- Please, do not stick values with units ex. Line 188, 190,
- I would suggest to add some reference to discussion between lines 216 – 233.
- Line 240: ‘we investigated the surface morphologies..’ unprofessional. Please use “The surface morphologies, wettability, microstructure and arc erosion property of cold-sprayed AgC composite coating with and without post-treatment were investigated in this paper” or similar.
Overall, the manuscript itself is very well structured and well written. Figures and graphs are clear. Reviewer highly recommend the paper for possible publication in Coatings.
Author Response
Dear reviewer, please see the attachment.
Author Response File: Author Response.pdf
