Damage Grading Evaluation of Thermal Barrier Coatings under CMAS Corrosion

Round 1

Reviewer 1 Report

The authors of the work applied a very interesting method to simulate the thermal cycling-CMAS coupling condition of the barrier coating. However, the article can be recommended for publication after correcting a number of comments:

In the Introduction, only the convection (plasma spraying) method of applying barrier coatings is considered, but there are others. I consider it possible to cite them and indicate the reason for choosing plasma spraying.

Setting up an experiment. The spraying parameters of Thermal barrier coatings YbYSZ and YSZ differ by 5-10% (current, Carrier gas flow rate, Spray distance), the porosity, hardness, length and density of cracks in the coating differ by approximately the same amount (taking into account the measurement error). It is not clear enough what still affects the significant increase in Lifetime during thermal cycling (in the case of using YbYSZ): changing the spraying modes or using a different powder. I would like to see the rationale for changing the spraying modes.

Specify the brand and manufacturer of all materials and equipment used, in particular: initial powders and substrate material, calcium magnesium aluminum silicate, atmospheric plasma spraying, hardness tester...

The graph (Line 232, Fig. 6a) indicates the crack length for YbYSZ-VI and YSZ-VI of about 90 and 115 mm, respectively, but this is not at all confirmed by figures 5f and 5I. In Fig. 5f, a crack of more than 200 mm is clearly visible, and Fig. 5L cracks are barely visible. It needs to be adjusted (possibly show the crack trajectory in Figs. 5f and 5I).

Of the 26 references, only 6 are from the last 5 years, possibly more recent publications exist.

Describe methods for measuring porosity, length, and density of cracks in a coating.

I would also like to recommend making a number of small corrections, for example:

Line 14, 39 - CMAS, move transcript from Introduction to Abstract

Line 81 - "The metal substrate used is GH-5188" needs more information about GH-5188

Line 82 - replace the letter "phi" with the sign of the diameter

Line 88 - "The same granulation process" it would be nice to specify which process

Line 90 - it is necessary to indicate the amount of ytterbium in the ceramic powder, but it is better to give the chemical composition of both powders

Line 94, Fig. 1c and f - increase image resolution or font size - captions are hard to read

Line 128 - "The diffraction Angle range" no capitalization needed

Line 156 - "of.thermal cycling" extra dot

Line 266, Fig. 8 - the authors need to explain the reason for such a significant drop in the intensity of diffraction patterns on samples Yb-III and Yb-IV

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The research addresses an important and relevant topic related to thermal barrier coatings used in high-temperature environments, specifically under thermal cycling and CMAS corrosion conditions. The investigation of YSZ and YbYSZ coatings provides insights into their potential application and performance in real-world scenarios.

Some Suggestions for Improvement:

While the research indicates that YbYSZ coating outperforms YSZ coating with an 83% increase in life, the paper lacks a comparative analysis of these results with other relevant research studies. 

The paper briefly discusses failure modes, but there is scope for more in-depth analysis of the failure mechanisms observed in both coatings. 

The paper does not include a section on limitations and potential future research directions. 

The paper provides experimental results without mentioning statistical analyses. Incorporating statistical tests to assess the significance of observed differences between the coatings and life stages may strengthen the study's scientific validity.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have presented quite interesting work on to simulate the thermal cycling-CMAS coupling condition of the barrier coatings. All comments have been corrected and the work can be published in present form.