Erosive Wear Behavior of High-Chromium Cast Iron: Combined Effect of Erodent Powders and Destabilization Heat Treatments
Round 1
Reviewer 1 Report
In this work, the correlation of hardness and erosive wear resistance with the microstructure of high chromium cast iron was studied. The manuscript is acceptable and of great interest, but needs some improvements for publication.
The introduction and review of the technical literature are very good. The experimental method is clear. However, I have relevant doubts about the discussion of the results. I also think that the conclusions can focus on the most important results of the manuscript. I reckon the following issues should be clarified:
Materials and Methods
1. In these high-chromium cast iron, some authors have considered it beneficial to perform tempering treatments after quenching in order to improve resistance to erosive wear. Why have you not considered this in your work?
2. For X-ray diffraction analysis, a Cu tube was used. In former investigations with Cr-alloyed iron castings, we have found that the Cu tube has difficulty in capturing any peaks emitting at low intensity. I recommend, if possible, to use a Mo tube to avoid fluorescence by reducing the background intensity so that no reflection is camouflaged.
Results
I have doubts about what phases the reagent attacks.
1. In figure 2 d) I have doubts about the phase you name. In the As-received condition, alloy 2 has 33.33% austenitic phase according to diffraction analysis. For this reason, I am surprised that no austenite is visible. In my experience, when I used the Fry reagent in this type of casting, it darkened the tempered martensite while the austenite had a light colour. Therefore, my question is: the martensite that appears labelled in the photo, is it not really austenite?
2. In Figure 4 a) I suggest you also to point out the retained austenite, since it is important as it is the receiving state. Austenite in SEM is usually seen as white plates with no apparent roughness, with martenisite needles inside. It can be seen just to the right of the M7C3 carbide label.
3. In Figure 5 a) I again have doubts about what you label as austenite and martensite. Maybe it is because of my lack of knowledge about this attack reagent, but martensite quenching is characterized by needles or plates with some roughness, while what you point out as martensite is a white plate without roughness. Inside these plates, I suppose that V shapes are martensite.
4. How is it possible that the hardness of alloy 2 is higher than that of alloy 1 after HT1 treatment, if alloy 2 has 20.15% austenite compared to 0.35% for alloy 1? Also, alloy 1 has about 25% more carbides than alloy 2. The same question arises after HT2 treatment. Please, I need further explanation on this.
5. I suggest you improve the quality of figure 9 b)
6. From Figure 10, I understand that for high (He/Ht) (as is the case for Al2O3), the ER value is independent of the He/Ht ratio. Similarly, for low He/Ht ratios, ER is dependent on this ratio. This leads to the conclusion that if the erosive powder is very hard, the hardness of the base material is indifferent to the erosive wear resistance. The hardness of the base material only influences when the erosive agent is softer. Is this correct? If so, why has the lowest ER been detected in the receiving state where there is more austenite and, therefore, it is softer? This result makes me think that the toughness of the matrix increases the resistance to erosive wear. Therefore, the hardness of the base material, is influential.
7. On the other hand, if we only focus on the data in Figure 10 for the Al2O3 erosive, it is observed that the ER decreases slightly as the ratio (He/Ht) increases. If (He) is constant (Al2O3), it means that (Ht) decreases. That is, ER decreases when the material is softer (higher content of austenite). It is important to point this out from my point of view because I have also observed this behaviour in my research. If the content of austenite has an influence on hard erosives, although logically to a lesser extent than on the softer ones, is it worthy to perform a thermal treatment when the erosive agent is extremely hard? Perhaps that would be a good conclusion.
Conclusions
1. The wording is excessively long. You include comments and explanations that are part of the results. You should simplify it a lot and focus on the most relevant conclusions you get from the work.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The article has a scientific character. The Authors applied correct research methods and used the appropriate measuring equipment. The content of the work is logically written. The manuscript contains ten figures and two tables. Figures and tables are properly prepared. Authors cited 64 literature sources.
The work concerns the resistance to erosive wear of chromium cast steels in the state after casting and heat treatment. The authors presented an interesting work, but it requires numerous improvements to be of satisfactory quality.
General remarks
1. It doesn't make sense to create a line graph for two data; better use a column chart.
2. In Figures 7,8,9, enter the error bars
Detailed comments
1. Line 107 Show the detail drawing from which the samples were cut
2. Line 116-125 More detail on HT1-3 heat treatment conditions in a separate table
3. Line 150 raw meal powder - enter the chemical composition of the abrasive in a separate table and the hardness
4. Line 151 give the uncertainty of the grain diameter measurement (write the result as X = d ± δ)
5. Line 167 give the formula instead of ER description
6. Figure 4, 5 photos are of poor quality, martensite is not clear, the remaining fragments do not allow for phase recognition, it is recommended to add the results of the EDS analysis
7. Figure 7, 8a, 8c, 9a, 9c As already mentioned, there is no point in such a plot, the straight line will always pass through two points, convert it to a column graph
8. Figure 8b, 8d, 9b, 9d photos not sharp and blurry, improve the quality of photos, it is recommended to add EDS analysis results
9. Table 2 give the measurement uncertainty (write down the result as X = d ± δ)
10. Figure 10 does not make the sense of the plot clear. Questions about this drawing:
- what do the dashed lines in the picture mean?
- Results for Alloy1 and Alloy2 are shown for different types of heat treatment or for one variant only? If for many treatments, then such a presentation does not make much sense.
- why regression notation in the form y = ax ^ b, shouldn't be ER = (He / Ht) ^ b?
11. Conclusion instead of a long description, give specific conclusions from the work in the form of points
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have considerably improved the article. However, there remains one important aspect that still needs to be clarified. I am aware that it is not the most important focus of your research, but please understand that what I am asking you to review in detail is an aspect that may raise many doubts for readers.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
Thank you for considering my comments. I will recommend publishing the work.
Author Response
The Authors would like to thank the Reviewer for his/her helpful revision that helped to improve the quality of the manuscript.
