CMAS Corrosion Resistance of Plasma-Sprayed YSZ and Yb2O3-Y2O3-Co-Stabilized ZrO2 Coatings under 39–40 KW Spraying Power
Leshchynsky Volf
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsReview
of the manuscript “Comparative study of the CMAS corrosion resistance of plasma-sprayed YSZ and Yb2O3-Y2O3 co-stabilized ZrO2 coatings under different spraying power”
Currently, great attention has been paid to the damage on TC called the calcium–magnesium–aluminum–silicates (CMAS) environmental attack. CMAS is the result of melting mineral debris containing silica, such as dust, sand, and ash, and the penetration of the molten CMAS into the porosity or the inter-columnar spaces of deposited YSZ. Yttrium from the coating is depleted during this process. So, the paper topic is actual and hot at this moment. The authors clearly show that “…Compared to YSZ coatings, YbYSZ coatings have lower thermal conductivity, higher hardness and elastic modulus, longer lifetime under thermal cycling-CMAS conditions, and lower penetration and degradation depths. Under thermal cycling-CMAS coupling conditions, the optimal power range for the longest thermal cycling lifetime for both coatings is 39-40 kW.” The paper is clear and useful. The scientific level is high. English is good. I recommend the manuscript for publication with minor revisions. Some comments are below.
Line 85: The absence of a detailed description of the powder before paragraph 2.1, “Deposition of the TBCs”, is a notable gap in the manuscript. Such a description is crucial for readers to fully understand the context and implications of the subsequent sections.
Lines 222- 224: It is difficult to understand the sentence “…By comparing the cross-sectional morphology of the two coatings at different power levels in Fig. 2, it can be clearly observed that although the preparation process parameters for the two coatings do not differ significantly, there is a considerable difference in their porosity”. The influence of power on the porosity is clearly seen in Fig.2. There are no other technology parameters that affect the porosity.
Lines 227-231: The information “…The images obtained using the above method were processed with the image analysis software ImageJ [43]. The pore structures in the images were extracted and converted to binary images, and the contrast was adjusted. The porosity of the coating was calculated as the ratio of the pore area to the total area in the selected images. The porosity of the sample was taken as the average porosity of the selected positions” needs to be presented in the p.2 “Experimental procedure.
Lines 237-238: The authors’ explanation “….This is because the YbYSZ coating, compared to the YSZ 237 coating, is doped with ytterbium, which increases the crystallinity of the coating to some extent” needs to be proved
Line 290: The authors do not share the influence of porosity and alloying on the thermal conductivity in p. 3.2.1. Thermophysical properties of as-sprayed coatings.
Lines 379-380: The authors state “…At higher spraying power, the coating is denser with fewer inherent defects, effectively blocking CMAS penetration.” However, there is no explanation of inherent defects' influence on thermal conductivity.
Line 402: Unfortunately, the authors do not show the grain morphology and do not analyze the influence of the grain boundaries on the thermophysical properties in p. 3.3.2. Cross-sectional morphology of coatings under thermal cycling-CMAS coupling conditions
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsDear authors of the article.
The presentation of material needs to be improved. Please correct my comments in the PDF file.
Show the original results obtained also in the conclusions.
After correction, the article may be recommended for publication.
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors1) Please expand the introduction and include more works on YbYSZ TBCs. Analyse the deposition parameters, microstructure and CMAS corrosion resistance.
2) Did you sunblast the BC after deposition to increase roughness? If not why?
Did you heat-treat the BC for diffusion and improved adhesion to the substrate?
3) Add a table with the chemical composition of the MCrAlY, YbYSZ and YSZ powders used in this work.
4) Figure 5: Several peaks have not been assigned to a phase.
5) "Within the scope of this study, the hardness and elastic modulus of the YbYSZ coatings are greater than those of the YSZ coatings"
This is not true. According to figure 7a, hardness values are comparable. Any differences fall within the experimental standard deviation.
6) Fig12k: How many different measurement were conducted per configuration? Error bars appear to be very consistent for CMAS corrosion penetration.
7) What is the coefficient of thermal expansion of the YbYSZ compared to YSZ? Are there any concerns of premature spallation due to different coefficients of thermal expansion with BC and substrate?
My closing comment is that this is a good work with many interesting results and good analysis.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsDear authors.
I have carefully reviewed the article you corrected.
You took my comments into account and corrected the conclusions.
I think the title of the article can also be corrected.
Your article may be recommended for publication.
Comments for author File: Comments.pdf
To improve your understanding of what you write in the future, you need to logically connect your results with facts and pictures.
Author Response
Comment 1: I have carefully reviewed the article you corrected. You took my comments into account and corrected. I think the title of the article can also be corrected. Your article may be recommended for publication.
Response: Respond: Thank you for your suggestion. Changes have been made to the title of the paper and to the errors in the paper. Relevant changes can be seen in the revised draft.
