Surface Oxidation Behavior and Wear Performance of a Fe-21.3Cr-3.5Al-0.5Ti-0.4Zr Steel
Round 1
Reviewer 1 Report
Dear authors,
This manuscript investigated oxidation and wear performance of Fe-21.3Cr-3.5Al-0.5Ti-0.4Zr in order to fabricate spot welding location pins.
The result obtained may certainly be useful in automobile industry.
However, I think that this paper can be accepted only after revision of this paper considering the comments below.
Major Comments
- How many times did the authors measure the mass gain for each sample? The authors suggested that the mass gain shown in Fig.2 presented a three-stage characteristic. However, the change in the thickness of oxide layer shown in Table 3 was not a three-stage characteristic. Please clarify this contradiction.
- It was difficult to evaluate the grain size from the surface morphologies shown in Fig.4. I think that accelerating voltage (20kV) was too high to observe the surface morphologies after oxidation. If authors have other images taken by lower accelerating voltage, please change the images.
- Relationship between the structure and the thickness and the hardness of oxide scale formed at different temperature was not clear. As an example, why was the hardness of oxide scale formed at 1340oC the highest even though the oxide scale was porous as the authors mentioned (line 142 in page 8) ? These points are important in this paper, therefore, should be discussed in more detailed.
- How much did the wear performance of the spot welding location pins which the authors suggested in this study improved comparison with an existing one?
Minor Comments
- Please capitalize Fe-Cr-“A”l. (line 32 in page 1)
- It is better that the authors add the information about oxidation atmosphere. For example, in air, in oxygen.
- In Table 2, is “wt.%” correct?
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
This manuscript has reported producing Fe-21.3Cr-3.5Al-0.5Ti-0.4Zr alloy for application of spot welding location pins in automobile industry. The experiments are well designed, and the results are credible. I think this work can be considered for publication after major revisions:
- The literature review is very descriptive and doesn't clearly highlight the current gaps in the field, which underpins the current investigation. More critical and comprehensive literature is needed.
- Experimental details section – What was the roughness of the disc?
- Experimental details section – What was the load during wear tests.
- Experimental details section – What was the diameter of sliding track during the tests?
- Experimental details section – How many times tribological tests were repeated? It is really important in such research.
- Experimental details section – What kind of pins you used in your research (rounded of flat)? If flat - how the intimate contact between samples was ensured?
- Result and discussion section – Does Figure 8 show an example or an average value of wear tests? There is no information about standard deviation of the results or error bars in tribological tests.
- Result and discussion section – Authors should point out the sliding directions on the surface texture (Fig. 10).
- What are the advantages of using this alloy over other materials used for location pins? Have the authors studied their practical application? Please, give more information.
- Carelessness of the text should be corrected (eg. page 1, line 16 and 18 – should be space after “at” and “from”; page 1, line 32 – should be Fe-Cr-Al etc.).
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Review of paper no. metals-880283-v1 titled Surface oxidation behavior and wear performance of a Fe-21.3Cr-3.5Al-0.5Ti-0.4Zr alloy by J. An et al.
The authors studied the oxidation behavior of Fe-Cr-Al-Ti-Zr alloy at 1120-1340 °C. An alumina (Al2O3) layer formation was found. Furthermore, a hardness of the layer and wear performance (weight loss due to wear) have been studied. The paper brings in some valuable corrosion results. It is written in good English. On the other hand, the annealing time was relatively short (3 h). It is not clear whether a protective scale has been actually formed on the sample surface. The data are only disclosed but not truly compared to previous studies. The discussion of the results is not sufficient. The paper has to be major revised. The following comments should be addressed on revision.
1.Chemical composition shows that carbon was also present in your materials (Table 1). Therefore, please, consider naming it as steel instead of “alloy” in the entire paper.
2.The microstructure and XRD of the substrate (Fig. 1) are results, not experimental details. As such, they should be presented within the results section.
3.The oxidation experiments are not sufficiently described. What was the oxidation atmosphere? Flowing air? Oxygen? Please, specify it.
4.How did you record the sample mass gain? By TG? Please, specify it.
5.Fig. 2 shows the specific mass gain at different temperatures. The holding time at each temperature should be disclosed in the figure caption. Furthermore, the data should not be connected by a line since they come from separate annealing experiments.
6.Fig.3 shows the composition of the oxide scale. It is surprising to see FeO among products. Your material contains a sufficient amount of Cr (21 wt. %). As such, an external Cr2O3 scale should have been formed instead of FeO. How do you explain the absence of chromia (Cr2O3) in the scale?
7.How do you explain that a significantly smaller layer thickness was found at 1300 °C compared to 1220 °C? Have you observed any layer spallation?
8.It is not sufficiently clear from your results that a protective scale has been formed on the sample surface. The scale thickness shows a large variation (Table 3). Furthermore, the data do not obey an Arrhenius relationship. The annealing time was relatively short. Was a parabolic behavior actually observed? Kinetic curves (mass gain versus time) should be presented for several temperatures. This information is important with respect to high temperature oxidation resistance of your material. The parabolic rate constants should be compared to previously studied alumina forming materials (Oxidation of Metals (2017) 88:315–326; International Journal of Hydrogen Energy 36 (2011) 4580-4587; Materials 2020, 13(14), 3152).
9.Several microscopy images (Fig. 5, 6, 7, 10) have a poor contrast. It is very difficult to distinguish the microstructure and chemical composition of the oxide scale. Please, improve the contrast of these images.
End of comments
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear authors,
This paper is acceptable for publication after minor revision.
Minor comment
・Scale bar in Fig.4,5,7,10 should be improved.
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
I accept the authors' replies
Author Response
Thanks the reviewer.
Reviewer 3 Report
Review of paper no. metals-880283-v2 titled Surface oxidation behavior and wear performance of a Fe-21.3Cr-3.5Al-0.5Ti-0.4Zr steel by J. An et al.
This is a revised version of previously reviewed manuscript. Authors answered most of my comments. The paper is acceptable for publication subject to minor revision.
Comments:
1.lines 65-66: Remove word “datum” from the sentence. It should read “Each mass gain was an average of three samples.”
2.line 79: Remove “datum” from the sentence. It should read: “Each weight loss was an average of three samples”.
3.In the conclusion you claim that “performance of your material is comparable to that made of costly material imported from abroad”. Nevertheless, you have not compared your data to similar, previously studied materials. The oxidation behavior (scale thickness) should be briefly compared to previously studied alumina-forming materials. Recent references should be cited.
4.The scale bars in Figs. 4,5,6,7 and 10 are poorly visible. They need to be sufficiently magnified.
End of comments
Author Response
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Author Response File: Author Response.pdf
