Promoted Mechanical Properties and LBE Corrosion Resistance of FeCrAlTi-ODS Coatings Deposited by Magnetron Sputtering
, Jianwei Zhang 1, Zhigang Li 1,2,* and Hongtao Zhao 1,2,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript “Promoted mechanical properties and LBE corrosion resistance of FeCrAlTi-ODS coatings deposited by magnetron sputtering” deals with the deposition and characterization of FeCrAlTi-ODS coatings, targeted for an application regarding Lead cooled fast reactors. The manuscript is well organized and clearly written describing first the deposition process and then presenting the results regarding the characterization of such coatings, in line with the proposed application.
Nevertheless, some issues have to be addressed and clarified before being accepted for publication:
Abstract: please define ODS when using it for the first time
Line 16 an 17, please rephrase or condense the two sentences. Use of “being” is inappropriate the second sentence
Line 18, nickel is misspelled.
Results and discussions:
Line 151-152 please clarify what “intensity for the magnetron ion splash” means. The bias voltage usually affects the conditions to the substrate, arriving fluxes and energy, not the magnetron sputtering process, at the target.
Line 161-162 , a quite vague and confusing explanation is given for the differences between composition of the target and the coating. First of all, the target composition obtained by the same method should be given as reference to provide comparison. Second of all, the differences are typically related to : different sputtering yields of elements, different transport to substrate , due to atoms size and mass, effects of re-sputtering selectively the growing film when increasing the bias voltage. Please clarify all these aspects.
Line 163-164 it is unclear why the shape of the sputtering race-track, assuming that this is phenomena in question, would affect the differences in composition. It can affect certainly the uniformity of the coating, and this is an aspect that should also be discussed.
Lines 168-188, describes and explains the differences thickness between the three conditions (different bias voltage). This can be significantly simplified by taking into account the two main phenomena the lead to this: (i) higher re-sputtering of the growing film, when increasing the bias voltage, (ii) higher density of the coating, due to higher energy of impinging ions. These aspects have to be discussed in relation to experimental conditions, i.e. low pressure and small distance from target to substrate. Please clarify this section.
Line 192, please clarify what does “element migration” means in this case.
Line 211, it is said that the film is amorphous but has two peaks. Please clarify
Lines 213-214 a misleading explanation is given for the peak height behavior, when increasing the bias. Most probably it is due to increased crystallinity of the coating, it is a known effect when increasing the energy of ions arriving to substrate, and has no relation with the substrate (grazing incidence and relatively thick coating). Please clarify.
Line 229-230 it is said “the content of metallic Y in the film is not existent”. Please rephrase and/clarify. The content is not detectable, bellow detection limit or something similar.
Figure 7, the AFM images are presented and roughness values are discussed (line 245). Please double check the S2 sample. It appears that is more strongly dependent on the roughness of the substrates, judging by the lines that one can assume that correspond with the polishing of the substrate. S1 and S3 are in line with wht one should expect. A reference of raw substrate, without coating, could also be useful when interpreting the variations.
Lines 248-251 an explanation is given, regarding the “cleaning” effect of Ar ions. This is true, but keep in mind that the Ar ions also produce sputtering of the coating itself, so the smoother surface corresponds also to a ion polishing of the coating by Ar ions.
Section 3.2 mechanical properties, please justify the choice of the maximum load that was used, in relation with the penetration depth, the coating thickness and the “10% rule”, the depth that the indenter is calibrated for when using the Olliver&Pharr model.
Figure 8, it would seem more logical to present the values as Sub, 1, 100, 200V, it would avoid the drop between the maximum and minimum values of the parameters.
Figure 9, please give more space between curves, the overlapping makes them difficult to see. A reference curve with the uncoated substrate would also be useful.
Line 350 it is said “ the remaining thickness of the coating is relatively small.” Please explain this and give values in the context of smaller thicknessed of S3 samples (before corrosion ). Does it decrease even more?
Line 386 it is said “has not been cleaned with the mixed solution”, apparently making reference to a cleaning procedure that was not detailed in the text. Please clarify
Author Response
Comment 1：Abstract: please define ODS when using it for the first time
Response 1：Thank you for your suggestion. ODS has been defined in the abstract.
Comment 2：Line 16 an 17, please rephrase or condense the two sentences. Use of “being” is inappropriate the second sentence
Response 2：Thank you for your suggestion. According to your suggestion, the sentences in line 16 and line 17 have been modified to "The hardness (H) reaches 11.52 GPa (twice that of the bare substrate), and the elastic modulus (E) reaches 172.89 GPa", and the wrong spelling of Ni element has been corrected.
Comment 3：Line 151-152 please clarify what “intensity for the magnetron ion splash” means. The bias voltage usually affects the conditions to the substrate, arriving fluxes and energy, not the magnetron sputtering process, at the target.
Response 3：Thank you for your suggestion. The "intensity for the magnetron ion splash" refers to the energy and flux of ions bombarding the substrate during magnetron sputtering, modulated by the substrate bias voltage. While the bias does not directly affect target sputtering, it enhances ion energy at the substrate, promoting denser coatings, improved mechanical properties, and altered thickness. This mechanism is central to the study’s demonstration of how bias voltage optimizes FeCrAlTi-ODS coating performance.
Comment 4：Line 161-162 , a quite vague and confusing explanation is given for the differences between composition of the target and the coating. First of all, the target composition obtained by the same method should be given as reference to provide comparison. Second of all, the differences are typically related to : different sputtering yields of elements, different transport to substrate , due to atoms size and mass, effects of re-sputtering selectively the growing film when increasing the bias voltage. Please clarify all these aspects.
Response 4：Thank you for your suggestion. Firstly, the original explanation is too vague; the content of each element in the coating should be compared with the composition of the target material. Secondly, the differences in the sputtering yield of elements in the coating are related to their atomic mass and radius. The higher oxygen content is due to the significant adsorption of oxygen during the magnetron sputtering process. Additional explanations are given in the manuscript.
Comment 5：Line 163-164 it is unclear why the shape of the sputtering race-track, assuming that this is phenomena in question, would affect the differences in composition. It can affect certainly the uniformity of the coating, and this is an aspect that should also be discussed.
Response 5：Thank you for your suggestion. The sputtering race-track’s shape indirectly influences coating composition and uniformity by causing local variations in sputtering yield and atom flux. While the study focuses on bias voltage effects, integrating discussions of race-track dynamics would improve the mechanistic understanding of compositional deviations and uniformity trends. This is particularly relevant for multi-element coatings like FeCrAlTi-ODS, where sputtering yield disparities between elements are significant.
Comment 6：Lines 168-188, describes and explains the differences thickness between the three conditions (different bias voltage). This can be significantly simplified by taking into account the two main phenomena the lead to this: (i) higher re-sputtering of the growing film, when increasing the bias voltage, (ii) higher density of the coating, due to higher energy of impinging ions. These aspects have to be discussed in relation to experimental conditions, i.e. low pressure and small distance from target to substrate. Please clarify this section.
Response 6：Thank you for your suggestion. When a negative bias voltage is applied to the substrate, energetic ions (e.g., Ar⁺, sputtered metal ions) bombard the growing film. At sufficiently high bias voltages (e.g., 200 V), these ions gain enough energy to eject atoms from the film surface (re-sputtering), reducing net deposition rate. At low pressures, ions experience fewer collisions with gas molecules, preserving their kinetic energy. This amplifies both re-sputtering and densification effects. The short path minimizes ion energy dissipation, ensuring ions strike the substrate with energies close to those predicted by the bias voltage.
Comment 7：Line 192, please clarify what does “element migration” means in this case.
Response 7：Thank you for your suggestion. "Element migration" here specifically refers to the selective dissolution and diffusion of metal elements in the 316L steel substrate under LBE corrosion. The FeCrAlTi-ODS coating effectively inhibits this process by forming a protective oxide film, thereby enhancing the corrosion resistance of the material.
Comment 8：Line 211, it is said that the film is amorphous but has two peaks. Please clarify
Response 8：Thank you for your suggestion. Due to the lack of atomic long-range order in the coating, the GIXRD spectrum shows a broad and diffuse diffraction peak. The authors classify the film as 'amorphous,' but the broad peak might be misinterpreted as a crystalline feature. Additionally, the diffraction peaks from the substrate material may also influence the results. XPS analysis (Figures 6b-f) reveals Y2O3 and metal oxides, which are amorphous or nanocrystalline in nature, as prepared during the magnetron sputtering process.
Comment 9：Lines 213-214 a misleading explanation is given for the peak height behavior, when increasing the bias. Most probably it is due to increased crystallinity of the coating, it is a known effect when increasing the energy of ions arriving to substrate, and has no relation with the substrate (grazing incidence and relatively thick coating). Please clarify.
Response 9：Thank you for your suggestion. The increase in the GIXRD diffraction peak of the coating is independent of the incident angle and the thickness of the coating. The relevant paragraphs have been deleted, see lines 207-220 in this paper.
Comment 10：Line 229-230 it is said “the content of metallic Y in the film is not existent”. Please rephrase and/clarify. The content is not detectable, bellow detection limit or something similar.
Response 10：Thank you for your suggestion. The description in the text has been changed to “The absence of a metal Y 3d peak at 155.6 eV suggests that the content of metallic Y in the film is below the detection limit”.
Comment 1 1：Figure 7, the AFM images are presented and roughness values are discussed (line 245). Please double check the S2 sample. It appears that is more strongly dependent on the roughness of the substrates, judging by the lines that one can assume that correspond with the polishing of the substrate. S1 and S3 are in line with wht one should expect. A reference of raw substrate, without coating, could also be useful when interpreting the variations.
Response 11：Thank you for your suggestion. Different samples were prepared under the same process conditions for coating preparation. Within a lower bias voltage range, the migration of deposited atoms on the substrate material's surface is restricted, preventing effective filling of micro-defects. The coating grows along the substrate's contour. As the bias voltage increases, Ra significantly decreases to 2.2 nm, resulting in a more dense and smooth surface, reducing the coating's surface roughness.
Comment 12：Lines 248-251 an explanation is given, regarding the “cleaning” effect of Ar ions. This is true, but keep in mind that the Ar ions also produce sputtering of the coating itself, so the smoother surface corresponds also to a ion polishing of the coating by Ar ions.
Response 12：Thank you for your suggestion. Your opinion is very correct. In the process of magnetron sputtering, Ar ions have a cleaning and ionic polishing effect on the substrate material. This mechanism shows that the bias in the process of magnetron sputtering can regulate the bonding force and surface morphology of the coating.
Comment 13：Section 3.2 mechanical properties, please justify the choice of the maximum load that was used, in relation with the penetration depth, the coating thickness and the “10% rule”, the depth that the indenter is calibrated for when using the Olliver&Pharr model.
Response 13：Thank you for your suggestion. According to the results of multiple experiments, in the nanoindentation test, 20 mN is selected as the maximum load, and the '10% rule' is applied: To avoid interference from the substrate on the hardness measurement of the coating, the indentation depth should not exceed 10% of the coating thickness (hmax≤0.1×Tcoating). The indentation depth of the substrate material is approximately 450 nm (Figure 8a). The maximum depth of the coating sample was about 300 nm (Figure 8a), which is significantly less than 10% of the coating thickness. The Oliver&Pharr model requires a deep enough indentation to distinguish between elastic and plastic deformation stages, usually requiring hmax≥50 nm. The indenter depth meets the calibration requirements of the Oliver&Pharr model to ensure accurate hardness and modulus of elasticity data (Figure 8b).
Comment 14：Figure 8, it would seem more logical to present the values as Sub, 1, 100, 200V, it would avoid the drop between the maximum and minimum values of the parameters.
Response 14：Thank you for your suggestion. According to your opinion, the Figure 8 has been modified.
Comment 15：Figure 9, please give more space between curves, the overlapping makes them difficult to see. A reference curve with the uncoated substrate would also be useful.
Response 15：Thank you for your suggestion. According to your opinion, the Figure 9 has been modified.
Comment 16：Line 350 it is said “ the remaining thickness of the coating is relatively small.” Please explain this and give values in the context of smaller thicknessed of S3 samples (before corrosion ). Does it decrease even more?
Response 16：Thank you for your suggestion. The description in the thesis that 'the remaining thickness of the coating is relatively small' is unreasonable, so the relevant description has been deleted. The smaller thickness specifically refers to the fact that the initial thickness of the S3 coating (5.73 μm) is smaller than that of the S1/S2 coatings, resulting in a relatively smaller remaining thickness after LBE corrosion.
Comment 17：Line 386 it is said “has not been cleaned with the mixed solution”, apparently making reference to a cleaning procedure that was not detailed in the text. Please clarify
Response 17：Thank you for your suggestion. "Has not been cleaned with the mixed solution" means that it has not been cleaned with the 1:1:1 CH3COOH, CH3CH2OH, and H2O2 mixed solution mentioned in Chapter 2.2. A large amount of LBE residue may still remain on the coating surface. The additional explanations were written in the manuscript.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe article considers anticorrosion materials for lead cooled fast reactors. The coatings investigated by the Authors are FeCrAlTi-ODS alloy. The introduction part is sound and the reason for research is well explained. Methodology part is also well described but there are certain issues concerning devices description. There is lack of information about ultrasonic device, magnetron sputtering device, tube furnace, GIXRD device, FESEM microscope type, X-ray emission spectrometer and atomic force microscope. If information about producer and type of these devices will be provided the Materials and method part will be complete. For Results and discussion part i have issues of editorial mater:
Table 3 and 4 no explanation of units
Figure 3 description does not explain which data is from which sample
Line 231 Table 5 instead of Table5.
Additionally I have two issues concerning text structure:
line 16 wrong unit notation GPa instead of Gpa
line 133 observed instead of observe
line 168-173 wrong font
After providing corrections above I recommend this article for publishing.
Author Response
The article considers anticorrosion materials for lead cooled fast reactors. The coatings investigated by the Authors are FeCrAlTi-ODS alloy. The introduction part is sound and the reason for research is well explained. Methodology part is also well described but there are certain issues concerning devices description. There is lack of information about ultrasonic device, magnetron sputtering device, tube furnace, GIXRD device, FESEM microscope type, X-ray emission spectrometer and atomic force microscope. If information about producer and type of these devices will be provided the Materials and method part will be complete. For Results and discussion part i have issues of editorial mater:
Comment 1：Table 3 and 4 no explanation of units
Response 1：Thank you for your suggestion. The units in Table 3 and Table 4 have been supplemented in the manuscript.
Comment 2：Figure 3 description does not explain which data is from which sample
Response 2：Thank you for your suggestion. Figure 3 shows the cross-sectional morphology and EDS energy spectrum of the S3 sample (the alloy coating prepared under 200 V bias)
Comment 3：Line 231 Table 5 instead of Table5.
Response 3：Thank you for your suggestion. Table5 has been revised to Table 5
Additionally I have two issues concerning text structure:
Comment 4：line 16 wrong unit notation GPa instead of Gpa
Response 4：Thank you for your suggestion. The unit has been changed to GPa
Comment 5：line 133 observed instead of observe
Response 5：Thank you for your suggestion. observe has been revised to observed
Comment 6：line 168-173 wrong font
Response 6：Thank you for your suggestion. In this manuscript, the editor has set the same font.
After providing corrections above I recommend this article for publishing.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsPromoted mechanical properties and LBE corrosion resistance of FeCrAlTi-ODS coatings deposited by magnetron sputtering
Reviewer comments for Manuscript coatings-3636577
- The abstract is well written. The abstract should encompass an introduction, a methodology, a summary of the conducted work, a knowledge gap, a contribution to the existing body of knowledge, and a conclusion. The hardness unit in the abstract should be changed to a Vickers hardness unit or BHN. GPa unit should be used for Tensile Strength, Young Modulus and Yield strength.
- The introduction is well written and cited. However, the last paragraph of the introduction should clearly state the objective or aim of the research. There should be a thorough discussion of past and present research. What is the contribution of this research to the body of knowledge? What specific gap in knowledge does this research aim to address? The introduction should be more elaborate and well-detailed. A paragraph on 316L stainless steel substrate should be discussed in the Introduction. Why is magnetron sputtering better than all other techniques? This should be justified in the introduction.
- The experimental procedures were well written. The section should detail the execution of the experiment, including all process parameters. Any equipment used should also be mentioned in this section. The description and the name of each piece of equipment should be stated in this section.
- How did the authors arrive at the process parameters? Were the process parameters taken from the literature? Were the parameters optimized? Was design of experiment (DOE) used to optimize the process parameters? This needs to be stated in this section. Optimized process parameters always have an influence on the outcome of coatings.
- What is the percentage purity of each powder? This should be stated in the experimental procedures section.
- How were the powders mixed? This should be stated in Section 2.
- What is the specification of the AFM?
- The results and discussion sections are well written and elaborated. The authors vividly explained the microstructural evolution of the composite coatings. But the results should be corroborated by the literature.
- A clear interface is visible between the alloy coating and the 316L substrate material, with no detectable pores on the surface of the alloy coating and the 316L steel substrate, indicating a strong adhesion between the FeCrAlTi-ODS alloy coating and the substrate….. Was this by physical examination?
- The thickness 133 of the FeCrAlTi-ODS coatings prepared under different negative bias voltages varies…… The measurement of coating thickness should be shown in the cross-sectional analysis of the coating. The thickness of the coatings can be measured by using Optical Microscopy.
- When the bias voltage is excessively high, it can lead to some adverse effects… Like what? Coarsed microstructures? This should be explained.
- The coating is stable and there is no element migration. The coating part contains a large amount of O element, which is related to the large amount of oxygen adsorbed during the magnetron sputtering process….. What was the Argon gas flow rate during the experimental procedure? This could be responsible for excess oxygen absorption.
Excess oxygen in coatings can have several effects depending on the specific coating material and application. In some cases, it can lead to improved properties like hardness and wear resistance, especially in certain thermal spraying processes. However, excessive oxygen can also negatively impact properties like surface energy, mechanical properties, and corrosion resistance, particularly in materials like amorphous carbon or certain metal alloys.
- Samples 1, 3 and 5 had excess oxygen while samples 2, 4 and 6 showed the opposite. What was responsible for this behaviour?
- All grammatical errors should be corrected in the manuscript.
- Recent references from 2021-2025 should be added to the manuscript.
- The paper should be accepted after the major corrections.
Comments on the Quality of English Language
This has been addressed in my comments
Author Response
Comment 1：The abstract is well written. The abstract should encompass an introduction, a methodology, a summary of the conducted work, a knowledge gap, a contribution to the existing body of knowledge, and a conclusion. The hardness unit in the abstract should be changed to a Vickers hardness unit or BHN. GPa unit should be used for Tensile Strength, Young Modulus and Yield strength.
Response 1：Thank you for your suggestion. Thank you for your kind comments on the manuscript. The hardness mentioned in this paper is the nano hardness and elastic modulus measured by the nano indentation instrument, where the unit of nano hardness is GPa.
Comment 2：The introduction is well written and cited. However, the last paragraph of the introduction should clearly state the objective or aim of the research. There should be a thorough discussion of past and present research. What is the contribution of this research to the body of knowledge? What specific gap in knowledge does this research aim to address? The introduction should be more elaborate and well-detailed. A paragraph on 316L stainless steel substrate should be discussed in the Introduction. Why is magnetron sputtering better than all other techniques? This should be justified in the introduction.
Response 2：Thank you for your suggestion. As you said, the purpose of this paper is：“Theobjective of this research is to identify effective anti-corrosion materials for fast reactors that use lead-bismuth eutectic (LBE) as a coolant”. In the introduction, the description of 316L stainless steel substrate and magnetron sputtering technology is added: “The base material selected is 316L austenitic steel for nuclear use, which is widely used as structural material in many reactors.” and “The coating deposition technology selected for this study is magnetron sputtering. The magnetron sputtering method offers advantages such as high deposition rates, excellent film continuity, and relatively low operating temperatures”. The revised content has been highlighted.
Comment 3：The experimental procedures were well written. The section should detail the execution of the experiment, including all process parameters. Any equipment used should also be mentioned in this section. The description and the name of each piece of equipment should be stated in this section.
Response 3：Thank you for your suggestion. The process parameters, experimental procedures and equipment descriptions involved in the manuscript are described in detail in Chapter 2, which can be seen in Chapter 2.1 (Deposition of FeCrAlTi-ODS coating), 2.2 (LBE corrosion tests) and 2.3 (Coating characterization) respectively.
Comment 4：How did the authors arrive at the process parameters? Were the process parameters taken from the literature? Were the parameters optimized? Was design of experiment (DOE) used to optimize the process parameters? This needs to be stated in this section. Optimized process parameters always have an influence on the outcome of coatings.
Response 4：Thank you for your suggestion. Parameters such as base pressure (3×10-4Pa), substrate temperature (150℃), sputtering pressure (0.6 Pa), Ar flow rate (120 sccm), deposition time (4 h), and target-substrate distance (4 cm) were chosen based on typical magnetron sputtering practices for ODS alloys and corrosion-resistant coatings. The approach was not a formal Design of Experiments (DOE) (e.g., orthogonal arrays or response surface methods) but a targeted single-factor optimization. By comparing outcomes at three discrete bias levels, the authors identified the optimal bias voltage (100 V for S2 coating) that yielded the thinnest, most compact structure with superior hardness (11.52 GPa) and LBE resistance. This targeted optimization directly influences the coating outcomes, as demonstrated by the superior performance of the S2 coating (100 V bias) compared to others.
Comment 4：What is the percentage purity of each powder? This should be stated in the experimental procedures section.
Response 4：Thank you for your suggestion. In this experiment, the alloy target is composed of two types of powders: a mixed metal powder of Fe-18Cr-13Al-8Ti and a dispersed oxide Y₂O₃ powder accounting for 8% of the total mass fraction. This has been supplemented in the manuscript.
Comment 5：How were the powders mixed? This should be stated in Section 2.
Response 5：Thank you for your suggestion. The FeCrAlTi-ODS coating was prepared by magnetron sputtering technology, and the target used is a metal-ceramic composite oxide. The composite target is prepared by powder metallurgy method, in which metal powder and ceramic powder in a certain proportion are fully mixed, and then formed by pressurization and sintering. The prepared target has a diameter of 76.2 mm and a thickness of 3 mm, and a copper backplate is inlaid on the back of the target to enhance its electrical conductivity.
Comment 6：What is the specification of the AFM?
Response 6：Thank you for your suggestion. The two-dimensional and three-dimensional morphology of the alloy coating analyzed by atomic force microscope mentioned in the manuscript is 5*5mm
Comment 7：The results and discussion sections are well written and elaborated. The authors vividly explained the microstructural evolution of the composite coatings. But the results should be corroborated by the literature.
Response 7：Thank you for your suggestion. The author cites more literature in the manuscript to verify the correctness of the conclusion.
Comment 8：A clear interface is visible between the alloy coating and the 316L substrate material, with no detectable pores on the surface of the alloy coating and the 316L steel substrate, indicating a strong adhesion between the FeCrAlTi-ODS alloy coating and the substrate….. Was this by physical examination?
Response 8：Thank you for your suggestion. It's not just a simple physical examination, as stated in Section 2.3, SEM with energy-dispersive spectroscopy (EDS) was used to examine the cross-sectional and surface morphologies of the coatings. Fig.1(a-c),2(a-c),and 3(a-c) show SEM images of the coating-substrate interface, which visually confirm the absence of pores and the clear boundary. The cross-sections were embedded in epoxy resin, ground, polished, and gold-sprayed before SEM observation (Section 2.3), ensuring high-resolution imaging of the interface.
Comment 9：The thickness 133 of the FeCrAlTi-ODS coatings prepared under different negative bias voltages varies…… The measurement of coating thickness should be shown in the cross-sectional analysis of the coating. The thickness of the coatings can be measured by using Optical Microscopy.
Response 9：Thank you for your suggestion. As you mentioned, the FeCrAlTi-ODS coating thickness measurements in the manuscript were determined by combining SEM characterization and EDS line scanning. The Fig. 5(a, c, e) shows cross-sectional SEM images of coatings S1, S2, and S3, with measured thicknesses of 6.88 μm (0 V), 6.70 μm (100 V), and 5.73 μm (200 V).
Comment 10：When the bias voltage is excessively high, it can lead to some adverse effects… Like what? Coarsed microstructures? This should be explained.
Response 10：Thank you for your suggestion. Higher bias voltage may lead to reduced coating thickness and deposition rate, As shown in Fig. 5, the coating thickness decreases from 6.88 μm (0 V) to 5.73 μm (200 V). High bias voltage enhances ion bombardment and back-sputtering, which reduces the net deposition of atoms onto the substrate, as described by Equation (2) [35, 36]. Fig. 10(e,f) and Table 5 show that the S3 coating (200 V) has more LBE residue (0.75 at.% Pb) on the surface after corrosion compared to S2 (0.14 at.% Pb). This suggests that high bias voltage may alter the oxide layer structure (e.g., FeCr₂O₄), making it less compact and reducing its protective effect. Secondly, it will also affect the mechanical properties of the coating and the corrosion resistance of the coating to LBE.
Comment 11：The coating is stable and there is no element migration. The coating part contains a large amount of O element, which is related to the large amount of oxygen adsorbed during the magnetron sputtering process….. What was the Argon gas flow rate during the experimental procedure? This could be responsible for excess oxygen absorption.
Response 11：Thank you for your suggestion. Firstly, Table 2 clearly indicates that the Ar flow rate was set to 120 sccm throughout the deposition process. This value is maintained constant for all coatings (S1, S2, S3) prepared under different bias voltages. Secondly, Table 4 shows that there is a large amount of O element in the coating structure, while the content is low in the substrate. Due to the incomplete guarantee of vacuum environment in the subsequent EDS test process, a large amount of adsorbed oxygen exists on its surface. The relevant description may not be accurate, and the relevant description has been deleted in the manuscript.
Comment 12：Samples 1, 3 and 5 had excess oxygen while samples 2, 4 and 6 showed the opposite. What was responsible for this behaviour?
Response 12：Thank you for your suggestion. The positions you mentioned are from Table 4, not multiple samples. Positions 1, 3, and 5 represent the coating structures prepared under different bias voltages, containing various coating elements. The higher oxygen content is due to a significant amount of adsorbed oxygen on the coating surface, which can be verified by XPS analysis. Positions 2, 4, and 6 show the EDS elemental distribution of the substrate material, 316L steel, which does not contain coating elements such as Al, Ti, or Y. The primary elements are Fe and Cr, with no significant differences observed at these points.
Comment 13：All grammatical errors should be corrected in the manuscript.
Response 13：Thank you for your suggestion. All grammatical errors will be checked in the revised manuscript.
Comment 14：Recent references from 2021-2025 should be added to the manuscript.
Response 14：Thank you for your suggestion. Currently, references from 2021-2025 account for about 50% of the total. And add some references in the revised manuscript.
Comment 15：The paper should be accepted after the major corrections.
Response 15：Thank you for your kind comments.
Author Response File: Author Response.pdf
