Lifetime Extension of Atmospheric and Suspension Plasma-Sprayed Thermal Barrier Coatings in Burner Rig Tests by Pre-Oxidizing the CoNiCrAlY Bond Coats
, Walter Sebastian Scheld 1, Daniel Emil Mack 1, Olivier Guillon 1,2 and Robert Vaßen 1,3Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors used microstructure analysis on the oxide formations, induced by vacuum and argon atmosphere on the metallic bond coat, and followed by the two different plasma spray methods. They compared the lifetime of the samples. They found the thermal cyclability was improved, while the pre-oxidation of the metallic bond coat was applied before the ceramic topcoat was implemented. They explained these scenes based on the experimental observations they took. After carefully reading, several recommendation and suggestions are raised.
1. The authors gave a good paper review and introduction to tell the readers what the problems they faced and the previous works were done. However, they used several acronyms but without giving a full name before usage, such as VPS, HVOF.
2. Please consider modify your title because there were no significant meaning of lamellar and columnar, even no mentioned in the text. MCrAlY bond coats shall be replaced by full composition of CoNiCrAlY bond coats. It is suggested as “Improved lifetime of thermal barrier system induced by the pre-oxidation of the metallic bond coat tested in a burner rig testing”.
3. Please check all the figures and tables in the whole text because I can only see “Error! Reference source not found”.
4. Please give a detailed description of the Table 1.
5. Please give a reference number for “A systematic study on the effect of partial oxygen ----performed by Matsumoto et al.” in the Introduction section. And it is strongly recommended to check whole paper text before re-submitted.
6. What are the chemical composition of Metco 233C and Metco 6608?
7. In Fig. 1, please indicate where the epoxy, substrate, metallic bond and ceramic bond are?
Comments on the Quality of English LanguageI do not see the figures and tables in the text, but the Error! Reference source not found. Please double check your manuscript again. Moreover, your English is understandable.
Author Response
Dear Reviewer,
Thank you very much for the quick review of the manuscript. Below you will find the detailed responses to your comments and suggestions. Furthermore, the corresponding revisions and corrections are highlighted in the manuscript in the attached file.
- The authors gave a good paper review and introduction to tell the readers what the problems they faced and the previous works were done. However, they used several acronyms but without giving a full name before usage, such as VPS, HVOF.
The entire manuscript was checked for abbreviations and all were introduced with their full names.
- Please consider modify your title because there were no significant meaning of lamellar and columnar, even no mentioned in the text. MCrAlY bond coats shall be replaced by full composition of CoNiCrAlY bond coats. It is suggested as “Improved lifetime of thermal barrier system induced by the pre-oxidation of the metallic bond coat tested in a burner rig testing”.
The title has been modified. In addition, in the introduction, it is now mentioned that lamellar coating microstructures are produced by the APS process and columnar microstructures are produced by the SPS process.
- Please check all the figures and tables in the whole text because I can only see “Error! Reference source not found”.
All errors have been corrected.
- Please give a detailed description of the Table 1.
Table 1 is now Table 2, as a table has been added giving the chemical composition and particle size distribution of the top coat materials used. Details have been added to the table of process parameters and two explanatory sentences have been added to the text.
- Please give a reference number for “A systematic study on the effect of partial oxygen ---- performed by Matsumoto et al.” in the Introduction section. And it is strongly recommended to check whole paper text before re-submitted.
The reference has been added at the end of the sentence.
- What are the chemical composition of Metco 233C and Metco 6608?
The chemical composition and particle size distribution of the two materials have been added in Table 1.
- In Fig. 1, please indicate where the epoxy, substrate, metallic bond and ceramic bond are?
The different layers in Figure 1 are now indicated. In addition, the different layers have been indicated in other images. The captions of all images where changes have been made are highlighted.
Comments on the Quality of English Language
I do not see the figures and tables in the text, but the Error! Reference source not found. Please double check your manuscript again. Moreover, your English is understandable.
The manuscript was fully checked again.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe research paper investigates what effect pre-oxidation has on different topcoats. This study compares the effect of pre-oxidation of APS and SPS coatings with the same bond coat. Modern research methods are used which affect the accuracy of the results.
1. Recommend adjustments to the title of the article, brevity in the title of the article increases the citation of the article. For example, it is possible to exclude coating structures from the title of the article, as laminar and columnar coatings are not mentioned in the text of the article, it is found only in the title of the article.
2. The abstract of the article is recommended to be edited. The abstract should briefly describe the main research methods or processing methods used, summarize the main conclusions of the article.
3. The abstract states that improved thermal cyclability has been demonstrated for coatings deposited by atmospheric plasma spraying (APS), suspension plasma spraying (SPS) and electron beam physical vapor deposition (EB-PVD) methods. However, the results obtained by EB-PVD method are not available in this work
4. In Figure 4, the designations should be changed for better clarity, preferably different shapes.
5. In Figure 5, a layer with a thickness of about 200 μm between the thin oxide layer and the substrate is clearly observed. Can you explain the formation of this layer? It is recommended to supplement with figures of APSpre-ox. and SPSpre-ox. samples.
6. In Figure 6, elemental mapping would be a great idea when studying the SEM of the cross sections.
7. When thermocycling the sample, it is recommended to apply TBС on all sides of the sample surface to avoid thermal expansion differences between the substrate and the coating.
Comments on the Quality of English LanguageIt is advisable to check your work for grammatical errors, such as the instance in Line 16 'More recently, however' and Line 303 where the word 'r.ed' is used. In particular, pay attention to the use of the words 'specimen' and 'sample', as their incorrect usage can be a common error in the text.
Author Response
Dear Reviewer,
Thank you very much for the quick review of the manuscript. Below you will find the detailed responses to your Comments and Suggestions. Furthermore, the corresponding revisions and corrections are highlighted in the manuscript attached.
The introduction has been revised. The difference between APS and SPS coatings has been explained.
- Recommend adjustments to the title of the article, brevity in the title of the article increases the citation of the article. For example, it is possible to exclude coating structures from the title of the article, as laminar and columnar coatings are not mentioned in the text of the article, it is found only in the title of the article.
The title has been modified. In addition, in the introduction, it is now mentioned that lamellar coating microstructures are produced by the APS process and columnar microstructures are produced by the SPS process.
- The abstract of the article is recommended to be edited. The abstract should briefly describe the main research methods or processing methods used, summarize the main conclusions of the article.
The abstract was revised and results have been described.
- The abstract states that improved thermal cyclability has been demonstrated for coatings deposited by atmospheric plasma spraying (APS), suspension plasma spraying (SPS) and electron beam physical vapor deposition (EB-PVD) methods. However, the results obtained by EB-PVD method are not available in this work
The EB-PVD coatings were mentioned in the abstract as the existing studies only investigated the effect of pre-oxidation of the bond coat on individual top coat systems. No comparison was ever made of the effect of pre-oxidation on different top coat systems. A comparison between APS and SPS coatings was made in this study.
- In Figure 4, the designations should be changed for better clarity, preferably different shapes.
The designations have been changed. Different shapes have been used.
- In Figure 5, a layer with a thickness of about 200 µm between the thin oxide layer and the substrate is clearly observed. Can you explain the formation of this layer? It is recommended to supplement with figures of APSpre-ox. and SPSpre-ox. samples.
The layer that can be seen is the bond coat. The different layers have now been labeled in the images. The deposition of this bond coat is described in section 2.1.
- In Figure 6, elemental mapping would be a great idea when studying the SEM of the cross sections.
The SEM images are backscattered electron images. A very typical structure for TBC systems can be seen in these images. The dark scale is the TGO, which consists of compact alumina. Due to the low atomic number of Al, it appears as a dark contrast. Since this structure is well known, an EDX mapping is not considered necessary.
- When thermocycling the sample, it is recommended to apply TBС on all sides of the sample surface to avoid thermal expansion differences between the substrate and the coating.
The layers of the specimens are designed like those of a blade in a real turbine. They cannot be coated from the inside. The selected sample geometry allows the coatings to be tested in the burner rig. The burner rig is a well-established test method that can specifically simulate the thermal conditions in a turbine. In addition, the differences in thermal expansion of the materials would remain even with an additional coating.
Comments on the Quality of English Language
It is advisable to check your work for grammatical errors, such as the instance in Line 16 'More recently, however' and Line 303 where the word 'r.ed' is used. In particular, pay attention to the use of the words 'specimen' and 'sample', as their incorrect usage can be a common error in the text.
The language of the text has been revised. Among other things, the word sample was avoided and replaced with more suitable alternatives.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article “Extended Lifetime of Lamellar and Columnar Plasma Sprayed Coatings in Burner Rig Testing due to Pre-Oxidation of the MCrAlY Bond Coats” by Jens Igel et al. is devoted to studying whether pre-oxidation has an effect on the service life of thermal gas coatings.
The article provides a comparative study of the structure and properties of coatings obtained by two different methods (APS and SPS) with/without preliminary oxidation. The authors analyzed such characteristics as phase composition, morphology, oxide layer thickness, and thermal cycling. The experimental part is well written and includes a table with the deposition parameters used. The conclusions are logical and justified. The presented manuscript is a complete and interesting study. Therefore, it can be published with minor edits.
1) Authors should change the Abstract to emphasize novelty and relevance.
2) The text contains a number of typos and inaccuracies. For example, there is no mention in the text of Figure 1 (lines 208-211), 2, etc. It is necessary to proofread the text carefully.
3) Which Al2O3 phase is shown in the XRF (α-,β, γ-)?
Comments on the Quality of English LanguageThe text contains a number of typos and inaccuracies. For example, there is no mention in the text of Figure 1 (lines 208-211), 2, etc. It is necessary to proofread the text carefully.
Author Response
Dear Reviewer,
Thank you very much for the quick review of the manuscript. Below you will find the detailed responses to your Comments and Suggestions. Furthermore, the corresponding revisions and corrections are highlighted in the manuscript attached.
1. Authors should change the Abstract to emphasize novelty and relevance.
The abstract was revised and the results were described. This should clarify the novelty of the study, the direct comparison of the effect of pre-oxidation on different topcoats.
2. The text contains a number of typos and inaccuracies. For example, there is no mention in the text of Figure 1 (lines 208-211), 2, etc. It is necessary to proofread the text carefully.
The manuscript was checked for the links to the images and tables. Furthermore, misspellings were corrected.
3. Which Al2O3 phase is shown in the XRF (α-,β, γ-)?
It should be an α-Al2O3 phase, as this is typically the dominant one in the TGO. But this has not been verified by measurements.
