A Study of Wear in Thin Coatings Applied to Convex-Concave Gearings
Round 1
Reviewer 1 Report
A study of wear in thin coatings applied to Convex-Concave gearings
MoS2 deposited on TiCN is another approach and worth to be published
What is the expected benefit of MoS2 deposited on TiCN compared to prior art?
ASTM A576-B1 is not descriptive as denomination. For readers, C45E (1.1191) or JIS S45C is easier to comprehense. The heat treatment procedure needs to be stated. Second, the authors state, that AIP (Arc-Ion-Plating) process is used at a substrate temperature of 420 °C during one hour. Such an annealing impacts the metallurgy and the slip-rolling resistance. The metallurgy after heat treatment and deposition is not described.
The correct wording for “load degree” is load stage as per ISO 14635.
In Figures 14&15 uncoated C45E test results are missing in order to illuminate the improvements by TiCN+MoS2. The paper is in view of this incomplete. Same for Figures 17&18.
Teer Coatings was a pioneer for MoS2 deposited on hard coatings. Prior art and such examples from Teet Coatings shall be referenced. MoS2 is suited for high Hertzian contact stresses, but is sensitive to humidity and MoS2 works best in vacuum. Such details are missing for readers.
How long last such a coatings and is it slip-rolling resistance?, questions not answered in this paper.
How matches sliding pin-on-disk tests with with slip-rolling in gears?
Author Response
Dear reviewer,
Thank you for taking the time to review and write comments on our article.
Point 1: What is the expected benefit of MoS2 deposited on TiCN compared to prior art?
Response 1: Coatings in gearings [20, 14]. In gearings, this layer can form a sliding layer in contact with the teeth.
Point 2: ASTM A576-B1 is not descriptive as denomination. For readers, C45E (1.1191) or JIS S45C is easier to comprehense.
The heat treatment procedure needs to be stated.
Second, the authors state, that AIP (Arc-Ion-Plating) process is used at a substrate temperature of 420 °C during one hour. Such an annealing impacts the metallurgy and the slip-rolling resistance. The metallurgy after heat treatment and deposition is not described.
Response 2: In the article designation of material is changed from ASTM A576-B1 to C45E
Heat treatment temperature 450°C.
Since the substrate tempering temperature (450 °C) was higher than the coating temperature (420 °C), no metallurgical changes in the substrate structure occurred.
Point 3: The correct wording for “load degree” is load stage as per ISO 14635.
Response 3: In the article is changed from “load degree” to “load stage”.
Point 4: In Figures 14&15 uncoated C45E test results are missing in order to illuminate the improvements by TiCN+MoS2. The paper is in view of this incomplete. Same for Figures 17&18.
Response 4: From the above figures 14&15 it can be seen that the roughness changes for both oils are almost the same, scuffing occurred at 11 stages of load. With uncoated gearings, scuffing occurred at 8 load stages [5]
Point 5: Teer Coatings was a pioneer for MoS2 deposited on hard coatings. Prior art and such examples from Teet Coatings shall be referenced.
MoS2 is suited for high Hertzian contact stresses, but is sensitive to humidity and MoS2 works best in vacuum. Such details are missing for readers.
Response 5: Teer Coatings applied MoS2 to machine parts, we did not find the possibility of applying it to gears. This is also because the gears are characterized by specific stress conditions in the teeth contact, which are not suitable for separate MoS2 (high pressures, sliding speeds and temperatures [1,2]). For this reason we used it only as a friction coating on TiCN. It is, of course, a matter of further research for its application to another hard coating.
Point 6: How long last such a coatings and is it slip-rolling resistance?, questions not answered in this paper.
Response 6: The most common gearing failurers are scuffing, pitting and fracture of the tooth. In this article we deal with the resistance of non-standard gearing to scuffing. The principle of the methodology of scuffing is based on tests on the Niemann tester, where the change scuffing depends on the change of roughness or weight loss. Therefore we did not solve the problem of slip-rolling resistance.
Point 7: How matches sliding pin-on-disk tests with with slip-rolling in gears?
Response 7: The basic laboratory method for investigating tribological properties is the Ball on disk method. However, the results of the work () have shown that these laboratory results in the case of gears are only indicative and are finally confirmed in the gears tests
Please see the attachment.
Sincerely, Roman Protasov
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear authors, respected editors of Lubricants journal!
This article has built logically. From the literature review, the need arises for the study of precisely these coatings. The methodology for creating coatings and their tests are understandable. The results has well discussed. This is a good article. But I have some comments.
- The literature review should indicate that the service life of gears can be increased through the use of various coating spraying methods.
- Why ASTM A576-B1 steel samples has hardened laser?
- Does this article need figure 4? And without this figure, everything is clear.
- In figures 5 and 6, I recommend signing where the coating is and where is the substrate. Put a scale marker in these figures.
- I recommend will discuss the two-stage dependence of the coefficient of friction (figure 9) in the text of the article.
- Why are the points connected by segments in figures 14 and 15? Draw the Rz axis in these figures.
- Why are the points connected by segments in figures 17 and 18? Is it possible to make an approximation dependence here?
I recommend correcting this article in accordance with my comments.
Yours faithfully,
reviewer
Comments for author File: 
Comments.pdf
Author Response
Dear reviewer,
Thank you for taking the time to review and write comments on our article.
Point 1: The literature review should indicate that the service life of gears can be increased through the use of various coating spraying methods.
Response 1: This literature has been added; required lifetime [13, 14,15,16].
Point 2: Why ASTM A576-B1 steel samples has hardened laser?
Response 2: Quenched which is currently the most suitable method for gearing (tooth side curve) and tempered
Point 3: Does this article need figure 4? And without this figure, everything is clear.
Response 3: This device (Figure 4) was made in the workplace of authors of the Institute of Transportation Technology and Design.
Point 4: In figures 5 and 6, I recommend signing where the coating is and where is the substrate. Put a scale marker in these figures.
Response 4: In these figures, the area of hard coating is highlighted and accordingly signed. The substrate is also signed in the drawings.
Point 5: I recommend will discuss the two-stage dependence of the coefficient of friction (figure 9) in the text of the article.
Response 5: However (in Figure 9), at a load of about 40 N, the friction coefficient increased from 0.1 to 0.5 to remove the coating. This value corresponds to the coefficient of friction of the substrate. In the case of the combined TiCN + MoS2 coating, the first phase with a low coefficient of friction is longer. This is due to the good sliding properties of the MoS2 layer.
Point 6: Why are the points connected by segments in figures 14 and 15? Draw the Rz axis in these figures.
Response 6: From the above figures it can be seen that the roughness changes for both oils are almost the same. The roughness change in FIG. 14 and FIG. 15 results from the measurement methodology FZG Test, ISO 14635-1: 2000 (12 load stages). Their interconnection is made in order to assess the trend change of Rz.
Point 7: Why are the points connected by segments in figures 17 and 18? Is it possible to make an approximation dependence here?
Response 7: The weight loss in Figure 17 and Figure 18 results from the measurement methodology FZG Test, ISO 14635-1: 2000 (12 load stages). Their interconnection is made in order to assess the trend change of weight loss.
Please see the attachment.
Sincerely, Roman Protasov
Author Response File: Author Response.docx
