Shrouding Gas Plasma Deposition Technique for Developing Low-Friction, Wear-Resistant WS2-Zn Thin Films on Unfilled PEEK: The Relationship Between Process and Coating Properties
, Christine Bandl 2, Reinhard Kaindl 1, Thomas Prethaler 1, Anna Maria Coclite 3 and Wolfgang Waldhauser 1Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Editor,
The manuscript (coatings-3256994) entitled ‘‘Shrouding gas plasma deposition technique for developing low friction-wear resistant WS2-Zn thin films on unfilled PEEK: The relationship between process and coating properties’’ can be published in the Coatings after minor revision.
My suggestions:
1- Write the keywords short, not like a sentence
2- Coefficient of friction is abbreviated as CoF in many places and COF in some places, especially on the graphic axis. It would be more accurate to make them all COF. CoF causes misunderstanding like cobalt fluoride. Or it should be the same abbreviation everywhere.
3- There are some spelling mistakes, please correct them; For examples, in line 122, Argon should be argon (not capital in sentence), in line 311, inWS2 , give space between in and WS2, in line 267, 150 A/20 L*min–1setting….. , it should be 150 A/20 L*min–1 setting, in line 158, 16 %, no space between number and percentage 16%, please check all text.
4- You can make the numbers on the graph axis in Figure 8 more legible.
5- The scientific part of the article is adequately commented. However, a detailed comparison with similar studies could have been made.
6- In some references, journal names are not abbreviated, e.g. references 7 and 34, please check this part again.
Ref.7: Metallurgical and Materials Transactions A.
Ref.34: Applied Surface Science.
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe paper presents the deposition of a low friction-wear resistant WS2-Zn thin films on unfilled PEEK using an atmospheric pressure plasma jet. The results on the improvement on the coefficient of friction of coated PEEKs were convincing, however, the manusript must be revised to address certain technical and scientific issues as listed below:
1. In the abstract, lines 19-20, the authors mentioned SEM with regard to the chemical composition, however, EDS and XPS were used for the determination of the chemical composition, hence, this section must be revised.
2. Figures 1, 2, and 3 can be deleted since the machines presented are provided by different companies and the authors did not make any alterations to these setups. If the authors would like to highlight the process, then a schematic diagram is more appropriate than showing the photos of commercially available devices.
3. Increasing the plasma jet current affected the film thickness and the tungsten component, however, the authors failed to discuss its effect on the changes in the coefficient of friction (COF). The authors discussed thoroughly the effects of changing powder gas flow but not the effects of changing the plasma jet current.
4. Did the authors perform statistical treatments on all the data presented, especially on the COF? If no statistical treatments are presented, it would seem from the visual inspection of figures 5, 6, and 7 that there is no difference if the powder gas flows were changed for all the plasma jet currents.
5. Did the authors perform aging tests on the wearability of the WS2-Zn thin films? Up to what point are the films physically and chemically stable?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsΤhe submitted paper deals with the effect of plasma spray deposition parameters of WS2-Zn thin films, deposited on PEEK, on the coating thickness and film tribological properties. It’s an interesting experimental work. My remarks are the following:
i) The novelty of this work must be highlighted in the manuscript. The authors must make clear if such coating systems applied on PEEK have been investigated by other researchers.
ii) Figure 8 is difficult to read. Since these diagrams contain all the valuable information from the investigations conducted, the author must enlarge them (the second diagram can be put down)
iii) Have the authors measured the hardness of the variously deposited coatings? In the conclusions, the authors mention that “Harder” coatings are generated by tuning the powder gas flow rate to lower 350 levels (i.e. 10 L*min–1 powder gas flow more beneficial than 20 L*min–1 powder gas flow). In addition, the Zn content variation inside the wear track represents a clear trend in terms of ductility properties, which is independent on the applied plasma current setting”. Based on which results, they claim the afore-described conclusions?
iv) According to the presented results (figures 5-7), WS2-Zn film improves the tribological performance of PEEK. However, the COF is slightly affected by the variation of powder gas flow and plasma current. Is there any explanation of this fact?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe revised manuscript sufficiently addressed all my concerns, hence, I recommend to accept the paper for publication in Coatings.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors replied satisfactorily to all reviewer's comments and the submitted work can be accepted for publication.
