Investigations into Power Plant Alloys’ (Inconel 718) Oxidation Resistance by Compound Composite (Cr2O3 + YSZ) Coatings
Round 1
Reviewer 1 Report
Manuscript number: coatings-2261637-peer-review-v1
Title of the manuscript: Investigations on Power Plant Alloys (Inconel 718) Oxidation Resistance by Compound composite (Cr2O3+YSZ) Coatings
Comments and Suggestions for Authors
The objective of the study was to estimate oxidation resistance of nickel-based superalloys EN8 and EN8/Yttria stabilized zirconia (YSZ)/Cr2O3 to high temperature in the open air at 1050°C for approximately 12, 24, 48, and 14 100 hours. Results indicate that the EN8 alloy exhibited greater weight variations over 48 hours at high temperatures, but coated EN8 exhibits higher performance under longer exposure than EN8 alloy.
I have found that the manuscript summarizes well experimental results, but I have some questions and observations for authors.
1. Line 57. TBCs means thermal barrier coatings. Please use all terms for the first time and after that used the abbreviations.
2. Line 96-100. Rewrite the sentences because are too ambiguous.
3. Line 181 thickness of 175m?
4. Figure 1 is not mentions in the manuscript text.
5. Line 180 Figure 2- SEM and XRD, but XRD is in Figure 3.
6. Line 190. Figure 3d does not exist.
7. Line 213 mentioned fig. 4b after 100h. Figure explained SEM and XRD after 24h. Correct this.
8. Figures 3-6 is for uncoated EN8? Do you have same results for coated EN8 to make some differences and observations?
9. Please check, explain and renumbered all the figures.
10. For more reliable results, did you think of doing electrochemical tests to evaluate corrosion resistance of coatings?
Author Response
Reply to Reviewer-1’s Comments
The objective of the study was to estimate oxidation resistance of nickel-based superalloys EN8 and EN8/Yttria stabilized zirconia (YSZ)/Cr2O3 to high temperature in the open air at 1050°C for approximately 12, 24, 48, and 14 100 hours. Results indicate that the EN8 alloy exhibited greater weight variations over 48 hours at high temperatures, but coated EN8 exhibits higher performance under longer exposure than EN8 alloy.
I have found that the manuscript summarizes well experimental results, but I have some questions and observations for authors.
- Line 57. TBCs means thermal barrier coatings. Please use all terms for the first time and after that used the abbreviations.
Reply: Carried out.
- Line 96-100. Rewrite the sentences because are too ambiguous.
Reply: Rewritten.
- Line 181 thickness of 175m?
Reply: Corrected
- Figure 1 is not mentions in the manuscript text.
Reply: Mentioned
- Line 180 Figure 2- SEM and XRD, but XRD is in Figure 3.
Reply: Corrected.
- Line 190. Figure 3d does not exist.
Reply: corrected.
- Line 213 mentioned fig. 4b after 100h. Figure explained SEM and XRD after 24h. Correct this.
Reply: Corrected.
- Figures 3-6 is for uncoated EN8? Do you have same results for coated EN8 to make some differences and observations?
Reply: for 3-6 for coated after different oxidadation period whereas Figure 2 D for uncoated after 100 hours of oxidation.
- Please check, explain and renumbered all the figures.
Reply: carried out.
- For more reliable results, did you think of doing electrochemical tests to evaluate corrosion resistance of coatings?
Reply: We are going to extend our work for molten salt environment in next technical papers.
Reviewer 2 Report
Comments for author File: 
Comments.pdf
Author Response
Reply to Reviewer-2’s comments
Reviewer 2
Improving the oxidation resistance of power plant alloys is certainly an interesting topic. There are numerous publications dealing with the use of atmospheric plasma spray to produce composite coatings. The manuscript is not carefully written, the description of the experiments is incomplete, experimental results are only presented but not evaluated, parts of the discussion are not supported by the experimental results. The whole paper must be carefully rewritten. Typographical errors are to correct. Some of the errors are listed below.
Abstract
Line 13: Typo. It must say (8% Y2O3).
Reply: Carried out.
Line 15: XRD means X-ray diffraction analysis. In the entire work, neither diffractograms nor 2-theta values of reflections from crystals are given, nor corresponding data discussed. Keywords The analytical methods used should be added.
Reply: Changed.
Introduction
Line34: Typo. It must say Inconel 718.
Reply: yes, carried out.
Line 37: Typo: The atomic symbol is Nb.
Reply: done.
Line 57: Abbreviations (here TBC) must be introduced the first time they are used. Methods and Materials
Reply: carried out.
Lines 119, 120: The correct term is chemical composition, not chemical makeup. Table 1 gives the composition of the substrate EN8. What about the data in Table 2? That is not clear. Is this the chemical composition of the three coating materials applied in the coating process (i.e., the starting materials)?
Reply: corrected.
Explain the terms top, bottom, and bond coating in connection with the information on the production of the coatings. Also, correct the typo on element C. It must be 0.005. What about the high value of V (vanadium)? Where does the metal come from?
Reply: Corrected in Table 1 and 2.
Line 122: Add the cast material name for better understanding.
Reply: Corrected
Line 124: Length, width and height are three dimensions. Consequently, it must be 30x10x3 mm3 .
Reply: Corrected.
Line 137-140: YSZ (a mixture of ZrO2 and Y2O3) and Cr2O3 in a ratio of 60:40 were sprayed on the substrate as indicated in the section. How was it done, simultaneously or sequentially? And what about the NiCrAlY bond coat listed in Table 2?
Reply: Corrected.
Line 145: The data were collected, not calculated.
Reply: corrected.
Line 154: In the Spray settings column, unify the units of measure. Use the symbols V for volts and A for amperes.
Reply: Corrected.
Lines 157-160: The information on the thermal tests needs to be formulated more clearly. Which samples were tested at a constant temperature of 1050°C? Why was the cyclic thermal loading only studied with the substrate material EN8. More clarity is needed to describe the procedure. There was no five-hour interval between each cycle, but each cycle lasted five hours (20 cycles of 5 hours each). The sample was heated from 900°C to 1050°C in 30 minutes. What happened afterwards? Was the temperature kept at 1050°C? How long? This information needs to be added.
Reply: corrected.
Line 166: It becomes clearer if Dm/mm2 is written here.
Reply: ∆ is added here.
Line 173: It should read EDS percent …
Reply: carried out
Lines 174-175: Where are the XRD analysis results?
Reply: They are EDS results no XRD results are included.
Line 177: For all devices used (sputtering, measuring), the name of the device, manufacturer and country should be given, as is the case here with the scanning electron microscope.
Reply: Provided.
Check lines 147, 172, 174. Results and Discussion
Reply: corrected
Line 183: Since yttria is not an element, you must write yttria stabilized zirconia.
Reply: Corrected.
Lines 181-183: Figure 1 shows the cross-sectional SEM image of the coating. In the text it is discussed that there is no interaction between the YSZ and the Cr2O3 layer. What do you conclude that from? Where is this visible? This conclusion is here without any evidence. At least elementary mapping of the elements of interest would need to be made to see if the two layers have the stated composition.
Reply:
Linn 190: There is no Figure 3d. You probably mean Figure 2d.
Reply: Corrected.
Line 192: All SEM images are distorted, i.e., compressed in the x direction.
Reply: Corrected.
Lines 203, 213, 218: As the figure numbering in the text is incorrect, the discussion cannot be followed. XRD data are not reported.
Reply: Figure numbering is corrected. Instead of XRD, EDS data are reported.
Lines 229, 233, 239, 243: The figures show an SEM image, an EDX spectrum and the intensity values of the peaks in the EDX spectrum, respectively. The tables given must be reduced to the essential information (element, weight %, atomic %, error %). In order to be able to compare the results of the oxidation processes of different durations, the data should be compiled in a table. This makes it easier to see changes in the composition. In addition, the captions must indicate whether the respective EN8 sample is coated or not. There are several elements determined in SEM/EDX that are not mentioned in Tables 1 and 2, where the composition of the support material and the coating materials is given. About 10 wt.-% P in one sample or 3.8 wt.-% Na in another sample – where do the large amounts of impurities come from?
Reply: Corrected.
Lines 249, 250: The conclusion about the phases of the coating is not proven. Only the missing XRD data can support the discussion here. The whole phase discussion only makes sense if the appropriate XR diffraction studies are presented.
Reply: presently, EDS data only provided as we are not using XRD.
Line 313: The mass gain has the unit mg/cm2 . Figure 7 shows data from four samples. Where are the corresponding SEM images and EDX data?
Reply: Figures 2-6 holding Sem and EDS data of this graph.
Lines 187, 193, 246: More typos. Discussion and conclusions are not supported by the results presented here. Inaccuracies and missing information in the experimental part and errors in the evaluation of the experimental results require a complete revision of the manuscript. References The citation style must be consistent and correspond to the style specified by the editor.
Reply: carried out.
Reviewer 3 Report
Reviewer's comments:
Although the oxidation resistance of (Cr2O3+YSZ) coatings on Inconel 718 alloy was investigated, some major revisions must be made before publication.
1. The test conditions of XRD should be supplemented, such as scanning speed, diffraction target, scanning current and voltage.
2. Please supplement the XRD spectrums before and after the oxidation of the YSZ/Cr2O3 coatings.
3. I suggest that the authors merge Figures 3-6, give the mass percentage and the atomic percentage, and remove the useless data.
4. In the introduction, the research background should be comprehensively summarized and discussed. Some important surface-coating techniques should be mentioned and discussed, such as halide activated pack cementation (HAPC) and hot dip silicon-plating (HDS). I suggest the author add the following missing references. Improving oxidation resistance of TZM alloy by deposited Si–MoSi2 composite coating with high silicon concentration; Synthesis of Si-NbSi2 coatings on Nb substrate by hot dip silicon-plating method under the various deposition temperatures; Microstructure and oxidation behavior of Si-MoSi2 coating deposited on Mo substrate at 600 °C and 900 °C in static air; Microstructure evolution and growth mechanism of Si-MoSi2 composite coatings on TZM (Mo-0.5Ti-0.1Zr-0.02 C) alloy.
5. For Figure 1. Please provide cross-sectional SEM image of the polished coating, and the YSZ and Cr2O3 layers should be marked in Figure 1.
6. References 1, 7 and 8 are too old. Please replace them with the latest report below. Evolution of surface morphology, roughness and texture of tungsten disilicide coatings on tungsten substrate; Formation of MoSi2 and Si/MoSi2 coatings on TZM (Mo–0.5Ti–0.1Zr–0.02C) alloy by hot dip silicon-plating method; Oxidation protection of tungsten alloys for nuclear fusion applications: A comprehensive review.
7. The figure captions of Figs. 3-6 is incorrect, the “XRD spectrum” should be replaced by “EDS spectrum” .
8. Please give the specific phase composition in Figs. 3-6, and the horizontal dimension of Figure 2 has been shortened, please give the correct SEM image.
Author Response
Reviewer 3 Reviewer's comments:
Although the oxidation resistance of (Cr2O3+YSZ) coatings on Inconel 718 alloy was investigated, some major revisions must be made before publication.
- The test conditions of XRD should be supplemented, such as scanning speed, diffraction target, scanning current and voltage.
Reply: There are no XRD analysis and EDS analysis was performed.
- Please supplement the XRD spectrums before and after the oxidation of the YSZ/Cr2O3 coatings.
Reply: There are only EDS spectrum not XRD. EDS spectrum is provided.
- I suggest that the authors merge Figures 3-6, give the mass percentage and the atomic percentage, and remove the useless data.
Reply: Corrected.
- In the introduction, the research background should be comprehensively summarized and discussed. Some important surface-coating techniques should be mentioned and discussed, such as halide activated pack cementation (HAPC) and hot dip silicon-plating (HDS). I suggest the author add the following missing references. Improving oxidation resistance of TZM alloy by deposited Si–MoSi2 composite coating with high silicon concentration; Synthesis of Si-NbSi2 coatings on Nb substrate by hot dip silicon-plating method under the various deposition temperatures; Microstructure and oxidation behavior of Si-MoSi2 coating deposited on Mo substrate at 600 °C and 900 °C in static air; Microstructure evolution and growth mechanism of Si-MoSi2 composite coatings on TZM (Mo-0.5Ti-0.1Zr-0.02 C) alloy.
Reply: Added
Reply:5. For Figure 1. Please provide cross-sectional SEM image of the polished coating, and the YSZ and Cr2O3 layers should be marked in Figure 1.
Reply: Provided
- References 1, 7 and 8 are too old. Please replace them with the latest report below. Evolution of surface morphology, roughness and texture of tungsten disilicide coatings on tungsten substrate; Formation of MoSi2 and Si/MoSi2 coatings on TZM (Mo–0.5Ti–0.1Zr–0.02C) alloy by hot dip silicon-plating method; Oxidation protection of tungsten alloys for nuclear fusion applications: A comprehensive review.
Reply: Added.
- The figure captions of Figs. 3-6 is incorrect, the “XRD spectrum” should be replaced by “EDS spectrum”.
Reply: Replaced.
- Please give the specific phase composition in Figs. 3-6, and the horizontal dimension of Figure 2 has been shortened, please give the correct SEM image.
Reply: carried out.
Round 2
Reviewer 1 Report
accept in present form
Author Response
Dear Sir/Mada, Thanks for your valuable suggestions to improve our paper and we appreciate your efforts. Regards Corresponding authorReviewer 2 Report
Comments for author File: Comments.pdf
Author Response
Dear Sir/Madam,
We appreciate your efforts and suggestions for improving article and we tried our level best to reply to your comments. We all thank you.
Regards
Corresponding author
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
Most comments have been incorporated into the revised manuscript.
It must be pointed out that there are still some discrepancies between the intensity of the Fe and Cr labeled EDS peaks on the one hand and the composition of the samples given in Table 4 (see Fig. 6c). The question also arises as to why no Cr Kα peak can be seen in the EDS spectra 3b, 5b and 5c, but the Cr content is given as over 50%.
Authors should carefully review and compare these data.
In addition, information should be added in Table 4 as to whether the composition given is in weight% or atom%.
Author Response
Dear Reviewer, Thanks for your overall suggestions in the view of improving the paper level. Regards Authors.
It must be pointed out that there are still some discrepancies between the intensity of the Fe and Cr labeled EDS peaks on the one hand and the composition of the samples given in Table 4 (see Fig. 6c). The question also arises as to why no Cr Kα peak can be seen in the EDS spectra 3b, 5b and 5c, but the Cr content is given as over 50%.
Authors should carefully review and compare these data.
Reply: modified.
In addition, information should be added in Table 4 as to whether the composition given is in weight% or atom%.
Reply: Added.
