Investigations on the Influence of Annealing on Microstructure and Mechanical Properties of Electrodeposited Ni-Mo and Ni-Mo-W Alloy Coatings
Round 1
Reviewer 1 Report
This work presents a study on investigations on the influence of annealing on microstructure and mechanical properties of electrodeposited Ni-Mo and Ni-Mo-W alloy coatings. The paper is acceptable for publication in the present form but some suggestions should be considered by the authors:
1) What is the thickness of the Ni-Mo and Ni-Mo-W coatings? Why this is not discussed by the authors? Is there an optimal thickness of the coatings?
2) The authors must give more information about the SEM and TEM images. They should try to adjust the sizes of the SEM images. The images have to be chosen with the same magnification and the scale has to be the original one.
3) Why the temperature regime of annealing was chosen at temperatures from 200 °C to 600 °C ?
4) The authors have to make some statistics and to show the nano-grain size distribution represented in histogram.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Authors,
it is my pleasure to review your interesting publication.
Here are some comments:
Abstract: Please be more precise regarding the wording of the sentences. Sometimes it’s a little bit confusing to the reader.
Gerneral comments: Please check the wording and meaning of the sentences of the whole text. Some are wrong and remain unclear to the reader (some examples are mentioned below).
The analyses of the coatings are in principal interesting, but as a substitute for hard chrome plating as mentioned in the introduction, your studies here are lacking with regard to coating adhesion on the substrate and tribological loading under corrosion environment. These both aspects are characteristic and particularly advantageous for hard chrome plating. Hard chrome plating is used for components exposed to wear at high temperatures (400 °C permanent loading or 1500 °C peak loading). Will this be fulfilled by the coatings you are investigated here?
Please change your motivation if this not the case.
Line 36: Nickel is harmful to health, also
Line 38: Nickel, W and Mo cost three times as much as chromium and are thus decidedly more expensive. Do the high prices justify the application in mass production or is it a niche application?
Line 41: ...alloy coatings are found to be…
Line54: Please remove one of the “temperature”
Line 54-55: Microcracks are desirable in hard Cr-plating absorbing lubricants applied for wear protection. The fine crack network also increases the ductility of the chromium layer, making it less brittle in relation to the high hardness. Is this undesirable with the selected layers thought as a replacement for hard Cr-plating? Why?
Line 81: scarce -> rare (scarce is an unusual wording)
Line 87: …and the influence of the annealing temperature…
Line: 98: Which acid was used for the activation?
Line 102: employed -> used
Line 10: engaged -> applied
Line 119: company name is “Bruker”
Line 118-120: The grazing incidence X-ray diffraction technique … was estimated phase composition -> unintelligible
Line 142: What is the layer thickness?
Table 1: Concentration data of the 2nd decimal place are unusual for EDS, since the measurement accuracy is 10 % and the detection limit is 0.5 %.
Figure 2b: The surface is very rough.
Line 285/ 297: First write out the long name and then later give the abbreviation (Hall-Petch)
Figure 7: The caption is incorrect, the same as Figure 6
Line 332: Please calculate and show the H/E ratio for all your measurements to be able to evaluate that this is supporting your statements
Table 2: Please keep the detection limit of EDS (0.5 %) in your mind. Hereto, see comments to Table 1.
Figure 10: Cracks are shown here. Are they due to the tribological loading? This would mean, that fatigue occured. What does it mean for the stability of the coating?
Best regards
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The research is focused on investigation the effect of annealing heat treatment on the microstructure of Ni-Mo-W coatings, their nano-hardness and tribological properties. I agree that Ni-W alloy coatings are one of the good options for hard chromium replacement due to its excellent hardness, corrosion and wear resistance [10, 11]. I also support as the authors claim that the heat treatment is an important and necessary technology to improve the mechanical performance of Ni-based coatings, such as Ni-Mo and Ni-W [27-32]. The choice of coatings is a logical combination of facts and technological knowledge in the field of both Ni-W and Ni-Mo coatings. Bearing in mind the arguments cited and the theoretical and literature introduction concerning the investigated coatings, I consider the aim of the work to be well-defined and important from a practical point of view.
Was there a sublayer (eg Ni) between the steel substrate and the Ni-Mo and Ni-Mo-W coatings?`
What was the thickness of the coatings and how was it measured?
In the case of electrolytically deposited coatings, for example, cracks may occur after the deposition process due to residual stresses. Were the residual stresses assessed? One of the standard methods of stress assessment is, for example, the method of examining the radius of curvature of the substrate after deposition (Stoney's formulas allow to convert this deflection into Pa) Is it possible, for example, to assess the stresses in these coatings using XRD methods?
Lines 106-111, Is it possible to further describe why the annealing time of 1 h was chosen. Were the influence of the annealing time and the rate of temperature rise on the properties and structure of these coatings also investigated?( Eg. Various graphs of T (t) or annealing cycles).
One of the basic tests in the investigations of anti-wear coatings is also the adhesion test in the so-called scratch tests. Were such tests were carried out?
Is it possible to show e.g. track profiles after ball-on-disk tests?
Is it possible to show e.g. sample indentation curves (Agilent G200 nanoindention tester) for the tested coatings before and after annealing?
In the case of anti-wear coatings, crack resistance assessments are also crucial, e.g. in indentation tests using Vickers or Rockwell indenters? Have such tests were done?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
