Synthesis, Microstructural Evolution, and Wet Wear Performance of an Fe55-Based Coating Reinforced with CeO₂ and TiN Particles Fabricated via Plasma Beam Spraying

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have provided significant data and analysis to demonstrate superior wear resistance of an optimal coating composition on Fe55. They have analyzed microstructural limitation of adding TiN and CeO2 into the Fe55 and optimized this reinforced coating for enhanced performance.

This work provides significant advancement towards material coatings as well as effect of microstructure on mechanical properties of materials. This manuscript can be accepted after addressing the specific comments listed below:

Have the authors collected any XRD data on these coatings? XRD would produce significant data on the lattice interactions of these materials and provide support to the microstructural analysis detailed in this study

Have the authors conducted any thermal study with this material? It would be curious to know the operating temperature limits (upper and lower) and can significantly impact the use cases of this material.

Is there any chemical limitation to this coating? Since the primary use of this material is valve technology, would a corrosive gases like ammonia and silane have any effect on the composition?

Although determining the long term effect will take significant time for data collection, it might be interesting to collect some electrochemical data like polarization curves to compare the corrosion behavior of the reinforced material against Fe55.

Author Response

 

Comments1: Have the authors collected any XRD data on these coatings? XRD would produce significant data on the lattice interactions of these materials and provide support to the microstructural analysis detailed in this study

Respone1: We appreciate the valuable comments from the reviewers. In our preliminary work, XRD analysis was conducted to determine the phases and lattice changes in the microstructure. However, in this study, we found that due to the low addition levels of TiN and CeO₂, their characteristic peaks were not detected in the XRD data. Additionally, the Ni content in the Fe55 weld layer exceeds 5%, resulting in a fully Fe-Cr-Ni microstructure , which overlap with the α-Fe characteristic peaks. However researchers confirm that the phase in Fe55 is γ-Fe and Cr₇C₃ in “Microstructure and wear behavior of (Cr,Fe)₇C₃ reinforced composite coating produced by plasma transferred arc weld-surfacing process. Surf. Coat. Technol. 2006, 201, 863–867”. To avoid raising concerns among reviewers and readers regarding the absence of TiN and CeO₂ characteristic peaks, we have decided not to include the XRD data in the manuscript to prevent potential misunderstandings. Thank you for your understanding.

 

Comments2: Have the authors conducted any thermal study with this material? It would be curious to know the operating temperature limits (upper and lower) and can significantly impact the use cases of this material.

Respone2: We sincerely appreciate the valuable comments and suggestions provided by the reviewers. In the initial design phase of this material, we focused primarily on valves for red mud transport pipelines and alumina transport pipelines, which operate within a temperature range of 75–85°C. Therefore, our initial design did not account for broader temperature applications beyond this range. However, we find your suggestions highly insightful. In future studies, we plan to conduct further tests on the weld layer’s thermal shock resistance within the 0–200°C temperature range. We will also investigate how temperature affects the weld layer’s corrosion resistance and wear resistance, thereby comprehensively characterizing its performance at different temperatures and expanding its potential applications. Thank you once again for your constructive feedback, which has greatly enhanced the scope of this study.

 

Comments3: Is there any chemical limitation to this coating? Since the primary use of this material is valve technology, would a corrosive gases like ammonia and silane have any effect on the composition?

Respone3: We sincerely appreciate the valuable comments provided by the reviewers. The valve material was specifically designed for use in red mud and alumina transport pipelines operating under alkaline conditions. Our industrial-scale experiments have demonstrated excellent performance of the valve sealing surfaces in these alkaline environments. However, we have not yet evaluated the corrosion resistance of the sealing surfaces in acidic environments or under exposure to corrosive gases. In future work, we plan to conduct comprehensive testing of the valve’s corrosion resistance under acidic and gaseous conditions to better understand its performance in diverse corrosive environments. This will enable further optimization of the material composition and microstructure, thereby expanding the material’s application potential in a broader range of industrial settings. Thank you for your constructive feedback.

 

Comments4: Although determining the long term effect will take significant time for data collection, it might be interesting to collect some electrochemical data like polarization curves to compare the corrosion behavior of the reinforced material against Fe55.

Respone4: We sincerely appreciate the valuable feedback provided by the reviewers. Currently, we are preparing a follow-up manuscript to specifically investigate the corrosion resistance of the weld layer in both reducing and oxidizing environments, aiming to assess the long-term serviceability of the valve in corrosive conditions. In the current submission, the focus has been on studying the microstructural evolution and friction and wear behavior of the valve. Electrochemical testing and related work will be addressed in future studies to further refine our comprehensive research framework. Thank you again for your invaluable suggestions.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper titled with “Synthesis, Microstructural Evolution, and Wet Wear  Performance of an Fe55-Based Coating Reinforced with 0.02wt% CeO2 and 2wt% TiN Particles Fabricated via Plasma Beam Spraying ” presents the application plasma beam spraying to create Fe55 alloy coatings with CeO₂ and TiN added to improve microstructure and wear resistance. Also, they investigated the co-working effect of CeO₂ and TiN  for the he most uniform microstructure with fully equiaxed grains  and no co-lumnar grains. The authors presented a problem that is potentially of interest to the readership. The study seems very interesting but it can be accepted after addressing the following comments:

1. The title seems limited to 0.02wt% CeO2 and 2wt% TiN, but the study optimize the effefect for different composition. I would suggest to rewrite the title for the broader perspectives.
2. Abstract must be updated by removing + sign and write in written words properly.
3. Last paragraph of introduction must be updated. Please write in words. Remove mathematical languages like + signs. Include your contribution and novelty as well.
4. Remove the line 108 “To further investigate the relationship between the co-addition 108 of CeO₂ and TiN and the grain boundary drag effect.” For repeating words.
5. Write caption ins consistent way. In figure 2 replace micrographs with SEM micrographs
6. Figure 3 caption you must elaborate OM graphs at first use.
7. In Figure 3 why did you use only one OM micrograph for FC2 sample? Why did use three for Fe55?
8. Authors must update figure 3 and its caption as well for better understanding.
9. Figure 4 numbering and caption is inconsistent. Must be updated for better understanding.

Author Response

Comments1: The title seems limited to 0.02wt% CeO2 and 2wt% TiN, but the study optimize the effefect for different composition. I would suggest to rewrite the title for the broader perspectives.

Respone1: We sincerely appreciate the valuable comments provided by the reviewers. Our original title indeed focused narrowly on a single chemical composition ratio, and we have taken your suggestion to expand the scope very seriously. The corresponding amendments have been made accordingly, and the revised title of the manuscript is now:

“Synthesis, Microstructural Evolution, and Wet Wear Performance of an Fe55-Based Coating Reinforced with CeO₂ and TiN Particles Fabricated via Plasma Beam Spraying.”

 

Comments2: Abstract must be updated by removing + sign and write in written words properly.

Respone2: Thank you for your valuable suggestions. The ‘+’ sign in the abstract has been removed as advised

 

Comments3: Last paragraph of introduction must be updated. Please write in words. Remove mathematical languages like + signs. Include your contribution and novelty as well.

Respone3: Thank you for your valuable suggestions. The ‘+’ sign in the abstract has been removed as advised

 

Comments4: Remove the line 108 “To further investigate the relationship between the co-addition 108 of CeO₂ and TiN and the grain boundary drag effect.” For repeating words.

Respone4: Thank you for your valuable suggestions, necessary revise has made

 

Comments5: Write caption ins consistent way. In figure 2 replace micrographs with SEM micrographs

Respone5: Thank you for your valuable suggestions, necessary revise has made

 

Comments6: Figure 3 caption you must elaborate OM graphs at first use.

Respone6: Thank you for your valuable suggestions, necessary revise has made

 

Comments7: In Figure 3 why did you use only one OM micrograph for FC2 sample? Why did use three for Fe55?

Respone7: Thank you for your valuable suggestions, The captions for Figure 3a (Fe55 optical micrograph) and Figures 3b/3c (SEM micrographs) have been revised to accurately describe the images.

 

Comments8: Authors must update figure 3 and its caption as well for better understanding.

Respone8: Thank you for your valuable suggestions, necessary revise has made

 

Comments9: Figure 4 numbering and caption is inconsistent. Must be updated for better understanding.

Respone9: Thank you for your valuable suggestions, necessary revise has made

 

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript deals with the plasma spraying coating of a 1025 carbon steel substrate by a Fe55 alloy filled with ceria (CeO2), titanium nitride (TiN), and a mixture of both. The ceramic filling is required to reduce the coating fragility due to the significant hardness variation related to the presence of a precipitated carbide (Cr7C3) hard phase in the welding area. Wet sand wear tests and slurry erosion experiments were performed in order to evaluate the tribological performance of different coatings. Such mechanical tests showed as the alloy filling by both ceria and titanium nitride powders leaded to the lowest hardness variability and therefore to the best tribological behaviour (wear resistance) of the alloy because the resulting microstructure was balanced and characterized by low leakage risks.

This manuscript has been carefully prepared, only the Experimental Section requires a few improvements; indeed, the suppliers for the Fe55 alloy, CeO2 powder, and TiN powder have not been provided (it is written just: ‘commercial source’) and these information are strictly required. In addition, the Supplier of the 1025 carbon steel substrate could be given. Both the producer and model of the Planetary-ball-mill used for the Fe55 and ceramic filler blending must be provided.

- The sentence: ‘spatial uniformity of nano-CeO2 dispersion’ (line 137) should be replaced by the sentence: ‘homogeneity of nano-CeO2 dispersion’.

- The acronym rpm is usually adopted to indicate the revolutions per minute; please, replace RPM with rpm.

- Contrast in the EDS maps given in Figure 2 should be increased, because some images (see a-2, a-3, e-3, etc.) are very dark and difficult to see.

- It could be useful to provide some more information about the hardness measurements that have been shown in the manuscript, like for example the type of hardness (Vickers?) and a Table with the average values and the related standard deviations point-by-point could be added.

- Figure 10 should be improved because for example the EDS spectra contained in this picture are so small that signals and Tables cannot be read.

- Figure 14a (and some others in Figure 14) has not been discussed in the manuscript text. All figures in this picture should be shortly discussed in the manuscript text.

 

Author Response

Comments1: The sentence: ‘spatial uniformity of nano-CeO2 dispersion’ (line 137) should be replaced by the sentence: ‘homogeneity of nano-CeO2 dispersion’.

Respone1: Thank you for your valuable suggestions, necessary revise has made

 

Comments2: The acronym rpm is usually adopted to indicate the revolutions per minute; please, replace RPM with rpm.\

Respone2: Thank you for your valuable suggestions, necessary revise has made

 

Comments3: Contrast in the EDS maps given in Figure 2 should be increased, because some images (see a-2, a-3, e-3, etc.) are very dark and difficult to see.

Respone3: Thank you for your valuable suggestions, necessary revise has made, the brightness of the image has been accurately calibrated

 

Comments4: It could be useful to provide some more information about the hardness measurements that have been shown in the manuscript, like for example the type of hardness (Vickers?) and a Table with the average values and the related standard deviations point-by-point could be added.

Respone4: Thank you for your valuable suggestions, necessary revise has made. New table was added into manuscript.

 

Comments5: Figure 10 should be improved because for example the EDS spectra contained in this picture are so small that signals and Tables cannot be read.

Respone5: Thank you for your valuable suggestions, necessary revise has made. New image was replaced into manuscript.

 

Comments6: Figure 14a (and some others in Figure 14) has not been discussed in the manuscript text. All figures in this picture should be shortly discussed in the manuscript text.

Respone6: Thank you for your valuable suggestions, necessary revise has made.

 

 

 

 

Reviewer 4 Report

Comments and Suggestions for Authors

The authors present a well-structured and comprehensive study on Fe55-based coatings modified with CeO₂ and TiN to improve wear resistance, using plasma spraying. The work is technically sound, the microstructural characterization is detailed, and the wear analysis is thorough.

The synergistic effect of CeO₂ and TiN is clearly demonstrated in terms of grain refinement, eutectic phase behavior, and surface performance under wet wear and erosion conditions. The mechanisms of nucleation, drag effect, and hardness uniformity are convincingly supported by both microstructural evidence and wear test data.

However, several clarifications, rhetorical adjustments, and minor additions would strengthen the manuscript’s clarity and impact:

1. The paper successfully relates grain morphology and hardness uniformity to wear resistance. However, a brief quantitative correlation (e.g., wear volume loss vs. % equiaxed grains or hardness variation range) would better support the conclusion.
2. The grain boundary drag vs. solute depletion mechanisms are well described, but the sequence of events during solidification is somewhat scattered. A schematic timeline showing particle interactions and phase formation would help the reader follow the logic.
3. Some phrases are repeated across multiple sections (e.g., "grain drag effect", "eutectic structure refinement", “synergistic effect”). Rephrasing or consolidating would improve flow.

4. • Abstract, line 26: “CeO₂ attached to TiN surfaces” -> consider “CeO₂ was adsorbed onto TiN surfaces”

   • Line 292: “dendritic coalescence... becomes facilitated” -> revise to “is enhanced” or “is promoted”

   • Replace phrases like “play as nucleation sites” -> “act as nucleation sites.

Author Response

Comments1: The paper successfully relates grain morphology and hardness uniformity to wear resistance. However, a brief quantitative correlation (e.g., wear volume loss vs. % equiaxed grains or hardness variation range) would better support the conclusion.

Respone1: We sincerely appreciate your valuable comments. During the study, we identified this issue and attempted to establish a mathematical model by correlating variables such as friction-induced mass loss rate, grain size, and hardness. Unfortunately, we were unable to refine this model effectively due to its non-linear behavioral outcomes. In future work, we plan to employ molecular dynamics (MD) simulations and finite element (FE) analysis to gain deeper insights into the relationship between friction and microstructure. This approach will enable a more comprehensive understanding of the mathematical relationships among grain size, microhardness, and friction-induced mass loss, thereby facilitating the development of a robust computational framework.

 

Comments2: The grain boundary drag vs. solute depletion mechanisms are well described, but the sequence of events during solidification is somewhat scattered. A schematic timeline showing particle interactions and phase formation would help the reader follow the logic.

Respone2: Thank you for your valuable suggestions, the schematic timeline was added into manuscript as an image

 

Comments3: Some phrases are repeated across multiple sections (e.g., "grain drag effect", "eutectic structure refinement", “synergistic effect”). Rephrasing or consolidating would improve flow.

Respone3: Thank you for your valuable suggestions, necessary revise has made

 

Comments4: Abstract, line 26: “CeO₂ attached to TiN surfaces” -> consider “CeO₂ was adsorbed onto TiN surfaces”

Line 292: “dendritic coalescence... becomes facilitated” -> revise to “is enhanced” or “is promoted”

Replace phrases like “play as nucleation sites” -> “act as nucleation sites.

Respone4: Thank you for your valuable suggestions, necessary revise has made