Microstructures, Corrosion Resistance and Wear Resistance of High-Entropy Alloys Coatings with Various Compositions Prepared by Laser Cladding: A Review

Round 1

Reviewer 1 Report

The article provides an overview of the state of the art on microstructures, corrosion resistance and wear resistance of high entropy alloys coatings. The work contains 7 figures, 1 tables and 50 references.

The review requires careful text editing. The main editorial notes for the work are given below:

- the record of the M2B phase should be corrected,

- figure 2 should be enlarged and figure 2f is of poor quality,

- figure 4 should be enlarged. In terms of content, it is stated that the work is relatively short, as for the review, it contains few drawings.

In terms of identifying wear and corrosion properties, the content is insufficient. For example, there is no analysis of the type of damage, views of the wear zone. It is recommended to significantly supplement the work with information on the tribological properties of the layers. This issue is important due to the given topic of the work.

Author Response

  Thank you very much for your great works and comments. We have carefully revised the manuscript. The revisions can be found in the revised version, and are shown with red font. The responses to your questions are as following.

Question 1

The article provides an overview of the state of the art on microstructures, corrosion resistance and wear resistance of high entropy alloys coatings. The work contains 7 figures, 1 tables and 50 references.

The review requires careful text editing. The main editorial notes for the work are given below:

(1) The record of the M2B phase should be corrected

(2) Figure 2 should be enlarged and figure 2f is of poor quality

(3) Figure 4 should be enlarged. In terms of content, it is stated that the work is relatively short, as for the review, it contains few drawings.

Answers:

    Thanks very much for your kind comments. We have revised the manuscript according to your suggestion.

(1) We have modified this problem based on comments. The M₂B phase has been changed to M₂B phase.

(2) We have modified this problem based on comments. Figure 2 has been enlarged and the quality of figure 2f has been improved.

(3) We have revised it. Figure 4 has been enlarged. The contents of Figure 4 are described in detail as follows:

 Figure 4 shows the SEM diagram of the cross-section morphology of coatings with differ-scanning rate ranging. It can be seen that the coating, fabricated at a scanning rate of 3 mm/s, possesses irregular cellular dendrites and granular carbide particles. With the scanning rate increasing, the dendrites become more regular and uniform in size. Compared with those coatings fabricated at various scanning rates, the HEA coating (P = 3.0 kW and v = 4 mm/s) exhibited more homogeneous and denser microstructure with no obvious microcracks. It show that slow scanning speeds reduced the content of W-rich particles and restrained the crack initiation while large scanning rates exhibited large numbers of cracks and W-rich particles because of the relatively lower laser energy.

Question 2

In terms of identifying wear and corrosion properties, the content is insufficient. For example, there is no analysis of the type of damage, views of the wear zone. It is recommended to significantly supplement the work with information on the tribological properties of the layers. This issue is important due to the given topic of the work.

Answers:

We have added statements on the identification of wear and corrosion in the revised manuscript. The added statements are presented as follows:

(1) Bingqian Wu et al. [36] studied the effect of Si content on the microstructure and wear resistance of FeCoCr0.5NbSi0.4 HEAs coating, the results showed that with the increase of Si content, the microstructure of the coating changed obviously, the M2B phase decreased, the eutectic structure also disappeared gradually, and the wear resistance of the coating at FeCoCr0.5NbSi0.4 was the best. During wear, the phases with low hardness values are fatigued off by the cyclic action of the WC balls, while the phases with higher hardness are not worn off, which shows that the wear mechanism of the FeCoCr0.5 NiBSi0.4 high-entropy alloy coating is mainly fatigue wear.

(2) Wenjun Hao et al. [37] did similar research, the results showed that the appropriate addition of Si can reduce the melting point of the alloy and improve wetting ability. Si also plays a role in grain refinement and improves the hardness and wear resistance of the alloy. The main form of wear on the surface of CoCrFeNi high-entropy alloy coating is adhesive wear, with the increase of Si content, the main wear mode changes to abrasive wear.

(3) Xulong An et al. [41]studied the effect of WC particles on the microstructure and properties of laser cladding HEA SiFeCoCrTi coating, and found that after adding WC, the microstructure of the coating changed from cellular dendrite to dense and fine dendrite, and the hardness of the coating increased, the friction coefficient decreased and the wear resistance improved. Alloy surface wear is a combination of abrasive wear and oxidation wear, and the wear surface is rough.

(4)Haijiang Wang et al. [43] studied the effects of laser power, scanning speed, and diamond content on the microstructure and wear resistance of FeCoCrNi-Mo composite coating. It is found that the laser cladding process parameters have a significant impact on the dilution ratio, graphitization, and wear resistance of the composite coating. As the laser power decreases, the wear area increases and the plough marks on the wear surface of Si3N4 balls increase. When the laser power was 3000 W, the wear area and the number of plough teeth increased sharply and the wear mechanism changed from adhesive wear to abrasive wear with the best wear resistance of the coating. When the laser power is 3000 W and the scanning speed is 50 mm/s, the composite coating has a uniform microstructure, the lowest dilution ratio, and the best wear resistance. It exhibited a mixed wear mechanism of adhesive wear and abrasive wear.

(5) Can Huang et al. [50] studied the dry sliding wear behavior of laser cladding TiVCrAlSi HEA coating on Ti-6Al-4V substrate. To avoid cracking, the substrate was preheated at 450 ℃. The results showed that there are only a few microcracks and pores in the coating section, and the coating has good metallurgical bonding ability. The Ti-6Al-4V substrate undergoes severe abrasive wear and adhesive wear. the wear surface morphology of the TiVCrAlSi high-entropy alloy coating indicates that the tests occur in a light wear state, with the main material loss mechanisms being oxidation, minor adhesive material transfer, and fragmentation and spalling of the adhesive material (including oxides).

(6) Meiyan Li et al. [51] studied the effect of ultrasonic shock treatment on the microstructure and properties of laser cladding Al0.5CoCrFeMnNi HEA coating. The results showed that ultrasonic impact did not change the phase structure of the coating, and there was an obvious solidification boundary in the cladding layer. After one impact, a thin plastic deformation layer was formed. With the increase of impact times, obvious impact marks appeared on the surface. In addition, the original precipitates at the solidification boundary were broken into smaller precipitates, and the particles inside the brain also had cracks. The minimum surface roughness and maximum surface hardness of the ultrasonic impact layer can be obtained by one impact, and the corrosion resistance of the impact layer was good. Corrosion morphologies showed that typical intergranular corrosion occurred on the surfaces of both kinds of layers while extensive corrosion pits appeared on the cladding coating surfaces.

Reviewer 2 Report

The paper ”Microstructures, corrosion resistance and wear resistance of high entropy alloys coatings with various compositions prepared by laser cladding: A review” is suitable for publication in Coatings Journal.

The research review summarizes the important topics of HEA coatings with good discussions. Just a point of view, I consider 50 references are a bit too few for a review article. In rest is ok.

Author Response

  Thank you very much for your great works and comments. We have carefully revised the manuscript. The revisions can be found in the revised version, and are shown with red font. The responses to your questions are as following.

Question 1:

The paper Microstructures, corrosion resistance and wear resistance of high entropy alloys coatings with various compositions prepared by laser cladding: A review” is suitable for publication in Coatings Journal.

The research review summarizes the important topics of HEA coatings with good discussions. Just a point of view, I consider 50 references are a bit too few for a review article. In rest is ok.

Answers:

Thanks very much for your kind suggestion. We have added 10 references in the revised manuscript.

The added references are shown as follows.

6. Xu, X.D.; Guo, S.; Nieh, T.G.; Liu, C.T.; Hirata, A.; Chen, M.W. Effects of mixing enthalpy and cooling rate on phase formation of AlxCoCrCuFeNi high-entropy alloys. Materialia. 2019, 6, 100292.
7. Otto, F.; Dlouhý, A.; Somsen, C.; Bei, H.; Eggeler, G.; George, E.P . The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy . Acta Mater. 2013, 61, 5743–5755.
8. Munitz, A.; Kaufman, M.; Nahmany , M.; Derimow, N.; Abbaschian, R. Microstructure and mechanical properties of heat-treated Al1. 25CoCrCuFeNi high entropy alloys. Mater. Sci. Eng. A. 2018, 714, 146–159.
9. Ni, C.; Shi, Y .; Liu, J.; Huang, G. Characterization of Al0.5FeCu0.7NiCoCr high-entropy alloy coating on aluminum alloy by laser cladding. Opt. Laser Technol. 2018, 105, 257–263.
10. Li, J.; Huang, Y .; Meng, X.; Xie, Y . A Review on High Entropy Alloys Coatings: Fabrication Processes and Property Assessment. Adv. Eng. Mater. 2019, 21, 1900343.
11. Shon, Y .; Joshi, S.S.; Katakam, S.; Rajamure, R.S.; Dahotr, N.B. Laser additive synthesis of high entropy alloy coating on aluminum: Corrosion behavior. Mater. Lett. 2015, 142, 122–125.
12. Hua, N.B.; Wang, W.J.; Wang, Q.T.; Ye, Y .X.; Lin, S.H.; Zhang, L.; Guo, Q.H.; Brechtl, J.; Liaw, P .K. Mechanical, corrosion, and wear properties of biomedical Ti–Zr–Nb–Ta–Mo high entropy alloys. J. Alloys Compd. 2021, 861, 157997.
13. Sun, Z.; Zhang, M.; Wang, G.; Yang, X.; Wang, S. Wear and corrosion resistance analysis of FeCoNiTiAlx high-entropy alloy coatings prepared by laser cladding. Coatings. 2021, 11, 155.
14. Qiua, X. Microstructure and corrosion properties of Al2CrFeCoxCuNiTi high entropy alloys prepared by additive manufacturing.J. Alloy. Compd. 2021, 887, 161422.
15. Wen, X.; Cui, X.; Jin, G.; Liu, Y .; Zhang, Y .; Fang, Y . In-situ synthesis of nano-lamellar Ni1.5CrCoFe0.5Mo0.1Nbx eutectic highentropy alloy coatings by laser cladding: Alloy design and microstructure evolution. Surf. Coat. T echnol. 2021, 405, 126728.

Reviewer 3 Report

- Abstract is way too long. Author should shortened the first part.

- In Introduction would be better to cite authors separately and not only write [7-18] or [19-25].

- Author should add to the end of Introduction usage in praxe if is some? Or is only theoretical?

- Author should check and correct all figures in his manuscript because some are not readable att all, in some is too big (a), (b)... text in figures should have similar size of font like other text in manuscript.

Author Response

  Thank you very much for your great works and comments. We have carefully revised the manuscript. The revisions can be found in the revised version, and are shown with red font. The responses to your questions are as following.

Question 1:

Abstract is way too long. Author should shortened the first part.

Answers:

Thank you for your comments. We have revised it. The modified part is as following:

Nowadays, high entropy alloys (HEAs) have become a hot research topic in the field of coating materials. However, HEAs have a large wide range of compositional systems, and the dif-ferences in composition inevitably lead to the significant variations in the matching process pa-rameters of laser cladding and post-treatment methods, which in turn give the coatings a broad range of microstructures and protective properties. Therefore, it is crucial to review and summarize the research progresses on laser cladding HEAs coatings to provide a reference for obtaining high-performance HEAs coatings and further expand the ap-plication of HEAs coatings. This work described the working mechanism of laser cladding and illustrates the advantages and drawbacks of laser cladding in detail. The effects of the addition of alloying elements, process parameters and post-treatment techniques on the microstructures and properties of the coatings were thoroughly reviewed and analyzed. In addition, the correlations between the chemical compositions of HEAs, process parameters of laser cladding, post-treatment techniques and the microstructure and protective properties of the coatings were investigated and summarized. On this basis, the future development direction of HEA coating was outlined.

Question 2:

In Introduction would be better to cite authors separately and not only write [7-18] or [19-25].

Answers:

Yes, we have corrected it in the revised manuscript.

Question 3:

Author should add to the end of Introduction usage in praxe if is some? Or is only theoretical?

Answers:

Yes, it is only theoretical.

Question 4:

Author should check and correct all figures in his manuscript because some are not readable att all, in some is too big (a), (b)... text in figures should have similar size of font like other text in manuscript

Answers:

We have checked every Figures carefully. The Figures with this error have been revised.

Round 2

Reviewer 1 Report

Thank you to the Authors for taking into account my comments. I will recommend publishing the work.