Preparation of WC Reinforced Co-Based Alloy Gradient Coatings on a H13 Mold Steel Substrate by Laser Cladding
Round 1
Reviewer 1 Report
The paper deals with the characterization of the effect of grading a Co-based alloy with a certain percentage of WC, which is increased progresively.
General comments:
The overall work is interesting and covers a nice spectrum of characterization techniques for the coatings. It adds new information to the existing state of the art, what must be acknowledged to the authors. Nevertheless, rReferencing in the Introduction could be slightly improved as there is a significant amount of literature related to the field. It would be very enriching for the paper to have some applications more detailed, such as if the goal of the development is an steady state involving process such as extrusion or a high takt time press stroke type process such as forging. Regarding the Experimental Methods, information is lacking for the results to be reproduceable by other authors, so improvements are requiered in this section.On the Results and Discussion section, some interpretations are arguable and thus would requiere some further explanations. This fact is carried-out to the Conclusions sections and thus, some changes are recommended there too. Please find below my detailed comments for the suggested improvement of the weak points found in the paper, and thanks in advance for taking them into accoun; I really hope they help increasing the impact of the work.
Specific Comments:
Title: The presence of WC in the coating should be pointed out in the title of the paper. Otherwise a reader looking for a work on WC reinforced coating could skip the paper thnking it refers to Stellite grades. Please consider this suggestion "Preparation of WC reinforced Co-based alloy gradient coatings on a H13 tool steel substrate by laser cladding".
Line 23. The term "furrow" doesn't fit with a wear mechanism. Please rework the phrase to refer to the wear track geometry instead of referring to wear mechanisms.
Line 34. I would reccommend the term "hot working tool steel" instead of "hot mold steel".
Line 37. Ref. [1] can also be accompanied by other refs. such as https://doi.org/10.3390/met9060694 introducing the use of H13 also in hot stamping processes.
Line 41. Please be aware that the sentece starting with "As we all know, the failure of the mold starts in the surface" is not actually always the case and should be modified to "As we all know, the failure of the mold starts most frequently in surface ". Many refrigerated H13 tools start the failure in the internal refrigeration channel stress concentraors such as shown in the geometry of https://doi.org/10.3390/met8020102 or other sort of stress concentrators. Please account for this fact if possible.
Line 59. Regarding the more and more "tailored property demand" a few more references could be cited on specific property tuning works made with laser cladding and involving H13 steel to underline it is a field of interest in the research community, such as https://doi.org/10.1007/s11661-019-05294-x or https://doi.org/10.3390/ma12030544 .
Line 66. Please explain the term "mutation", make a reference for its explanation or use another term of your choice more frequent in the literature.
Line 67. Depending on the laser cladding conditions and the material which has been selected for the coating, this sentece would not be true. Please underline that the bonding between the coating and the substrate is a critical issue, but please avoid stating in the paper that it is "easy to lose its effects due to cracking and falling off". In fact, my experience is that some industrial tools are known to be used with cracked coatings for long production runs, so cracking is netiher always critical.
Line 71. PLease avoid introducing the whole title of the work to keep an homogeneous style in citation.
Line 72. "Mutation" again. Did you mean transition?
Table 1. Please add in the text that the table refers to the specificaiton, not he actula composition of the sample you used. Include the actual analysis of your sample if possible.
Line 85. I would expect in this paragraph to find a reference on the actual heat treamtent condition and hardness you decided to use for the H13 substrate. This information (hardness) is found further in the text but its value doesn't fit a service condition for a H13 tool steel. This is a major issue in the work that must be justified somewhere in the text. If you are using H13 in annealled condition, what is actually the point of not using a cheaper, more machinable, higher thermal conductiviy steel? Or cast iron? This explanation must be included somewhere in the text please.
Table 2. Please make a note saying this was the actual composition and who measured it (your lab or the supplier). Grade statement or specifcation would also be welcome.
Line 99. Ground, milled and oxidezed surfaces work just fine with laser cladding. Oxides even act as fluxants in the melt pool, what can be beneficial if controlled. Please just note that you decided to condition the surface instead of saying that they "need to be treated".
Line 100. Please supply particle size and distribution if possible.
Line 105. Correct the symbol for "ºC".
Line 106. Correct the symbol for "ºC" and subsititute "residual" for "thermal".
Table 3. Please add another Table with the Laser Cladding conditions so that other researchers can replicate (carrying gas, protection gas, power, powder feed, optic, number of runs or total thickness -noted in figure 4-, run length and cladding speed).
Line 118. Please change "corroded" by "etched".
Line 121. Please if possible add the value for standard deviations in addition to averages.
Line 126. Please add more information for reproducibility: pin material, pin geometry, test temperature and humidity and frequency.
Line 131. A figure explaining the exact position and orientation of the Charpy impact specimen features and the coating/substrate combination should be included. The explanations are not deterministic.
Line 139. Please add the bath volume and wheter there was any agitation or areation during the corrosion tests.
Figure 1. Please specificy which of the three coating conditions is shown in the figure.
Line 153. Please back the affirmation "very small" with a EDS line scan or similar.
Figure 3. The X-Ray diffrection pattern in these gradient coatings is very position dependent and the notes can be ambiguous. Plase consider the possibility of having 25%WC / 20%WC and 15%WC in the legend instead of the composition of the whole coating.
Figure 4. Please add error bars on the averages. An explanation behind the reason of using annealed H13 must be included somewhere in the paper. The differences are not actually relevant and this goes against the discussion and the conclusions. PLease note that, in the surface the three samples ahve 25%, 20% and 15% WC. How can it be explained that the first layer of WC15%+20%+25%, which has 15%WC is much softer that the last layer of WC5%+10%+15% having the same amount of WC? Tempering? Please explain and back it up with references if possible.
Figure 5.b. Consider the possiblity of black and white printing the text, lines are not distinguishable.
Line 207. Please address if "fine grain" refer to "grain size" or "particle size" and note it crearly i nthe text.
Figure 8, 9 and 12. Please add error bars if possible.
Line 280. Check the comments on Figure 4 and rework the conclusion accordingly if necessary please.
Thanks in advance for taking my comments into account. I hope all can be answered and the paper gets a higher impact capacity.
Author Response
Dear Reviewer:
Thank you for comments concerning our manuscript. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:
According to your suggestion, we have modified the titleof the article and marked it in red. According to your suggestions and requirements, we have modified line 23, line 34, line 41, line 66, line 72, line 99, line 105, line 106, line 118, Figure 3.and Figure 5. b., replaced and explained some words and sentences, and marked them in red. According to your suggestions, we have cited more references, such as https://doi.org/10.3390/met9060694,https://doi.org/10.1007/s11661-019-05294-x and https://doi.org/10.3390/ma12030544, and marked them in red. According to your suggestions, we havedeleted some words and sentences in line 67 and line 71. According to your requirements, we have modified Table 1.to give the specification of the actual sample and actual analysis, and marked them in red. In response to your question aboutline 85, I have given the heat treatment condition of the actual samples. In addition, the steel used in the test was H13 mold steel, not tool steel, and the “tool steel” appeared in the paper was a translation error. According to yourrequirements, we have made a note saying the actual composition in Table 2. is provided by the supplier. According to your requirements, we haveadded Table 4. to list the specific parameters of the laser cladding experiment, and marked them in red. According to your suggestion, I have added the material and geometry of the grinding specimen, test temperature and humidity and frequencyto the friction and wear test method, and marked them in red. According to yourrequirement, we have added the schematic diagram of impact test. According to your requirements, we have explained that Figure 1.shows the bonding condition of the coating and the substrate of the first sample. In response to your question aboutFigure 4., “How can it be explained that the first layer of WC15%+20%+25%, which has 15%WC is much softer that the last layer of WC5%+10%+15% having the same amount of WC?”, this phenomenon can be explained as: Due to the dilution effect of the substrate on the first cladding layer, the hard phase content of the first cladding layer is reduced, so that the hardness of the first cladding layer is not high; the density of WC hard particles is less than that of cobalt based alloy powder, so it will float up in the molten pool, resulting in a high content of hard phases on the surface of the cladding layer, thus greatly increasing the surface hardness. According to your requirements, we havepointed out the "fine grain" in line 207refer to "grain size".
According to your suggestions and requirements, we have added error bars inFigure 4., Figure 8., Figure 9. and Figure 12.We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. We appreciate for your warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you very mach for your comments and suggestions.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article is relevant and interesting. Modifying the surface of steel objects is indeed an important task. The quality of the presented materials is worthy. The structure of research does not raise questions. Recommendations to authors: Chapter 1 should be strengthened and the literature review should be more extensive. It is necessary to reveal the scale of the problem and clearly formulate the purpose of the study.
Author Response
Dear Reviewer:
Thank you for comments concerning our manuscript. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:
According to your suggestions and requirements, we have strengthened the introduction part and cited more references, revealed the scale of the problem and clearly formulated the purpose of the study. In addition, we have also carefully revised some words and sentences in the paper in order to improve the paper, and marked them in red.
We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. We appreciate for your warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you very mach for your comments and suggestions.
Author Response File: Author Response.docx
Reviewer 3 Report
The manuscript entitled “Preparation of Co-based alloy gradient coatings on surface of the H13 Steel by laser", presents a comprehensive and well thought out study on the Co-based gradient coatings with stress relieving effect with a view to bridge the knowledge gap in the emerging field of coatings. Despite the existing wealth of literature associated in this area, only a handful of papers have addressed the aspects of Co coating on H13 steel substrate.
Moreover, the research design and results are of good scientific value dissected through a critical discussion of far-reaching impact. The introduction section provides a valuable insight into the field of the study, and the necessity of the undertaken research is explained in a clear and convincing manner. The applied experimental methods are relevant and comprehensive.
The amount of the experimental and numerical data presented is quite remarkable, and its analysis highly rigorous. English is almost errorless, except for few minor misspellings and typos which can be rectified through further proofreading. Lastly, I must say that the manuscript is supplemented by an impressive number of references, despite which the contribution of the presented work stands out. To summarise, the reviewer recommends that the manuscript be published after the revisions recommended in “Comments to Author”.
A thorough proofreading is required to iron out grammatical errors and sentence structure. For example, the first sentence of the abstract maybe written as: “H13 die steel often fails as a result of physical and chemical effects such as wear, erosion and cyclic stress. Accordingly, the study evaluates Co-based gradient coating on an H13 steel featuring stress relieving effect”.The above is just an example, the whole paper needs to be carefully edited to avoid long winded sentences and grammatical errors. Please try to be as precise as possible.
Abstract 3rd line: by structure; are the authors referring to microstructure? The introduction section needs improvement; the following papers maybe cited.https://doi.org/10.1088/2053-1591/ab5bda
https://doi.org/10.1088/2053-1591/ab301c
Table 1: remain? Use remaining or balance (Bal.) Table 1 caption, write (wt.%) It will be of benefit to the wider research community as a whole to look at the future direction of this research. Thus a ‘future work’ section can add significant value. Section 2.2: Analysis methodology not “methods” What is the adhesion strength of coating? Please provide data if this is available. Conclusion: in this experiment? Does the authors mean to say, in this study?Author Response
Dear Reviewer:
Thank you for comments concerning our manuscript. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:
According to yourrequirements, we have thoroughly proofread the whole paper to eliminate wrong grammar and sentence structure, and the revised places are marked in red. According to your suggestions and requirements, we havestrengthened the introduction part and cited more references, revealed the scale of the problem and clearly formulated the purpose of the study, and marked them in red. According to yourrequirements, we have replaced “remain” in table 1 with “Bal”. In response to your question “What is the adhesion strength of coating”, it can be explained as:The coating prepared by the laser cladding method is metallurgically bonded to the substrate, and the coating and the substrate are almost integrated, so it is not necessary to measure the bonding strength of the coating and the substrate. According to yourrequirements, we have replaced “experiment” in conclusion with “study”.We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. We appreciate for your warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you very mach for your comments and suggestions.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Dear Authors,
Thanks for having taken into account my comments.
Regards,
Author Response
Dear Reviewer:
Thank you for your affirmation of our research. With your eager help, our paper has been greatly improved.
Once again, thank you very mach for your comments and suggestions.
Kind regaeds.
