PSI - Issue 60

Sarath Chandran Nair S. et al. / Procedia Structural Integrity 60 (2024) 564–574 Sarath Chandran Nair S./ Structural Integrity Procedia 00 (2023) 000 – 000

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After 6 cycles of strain cycling at 790K

After 6 cycles of strain cycling at 820K

After 9 cycles of strain cycling at 820K

After 9 cycles of strain cycling at 790K

After 12 cycles of strain cycling at 790K

After 12 cycles of strain cycling at 820K

After 15 cycles of strain cycling at 790K

After 15 cycles of strain cycling at 820K

Fig. 10. Observations of strain cycling tests of Nickel and Chromium coated specimens

6. Conclusion Qualification of thermal barrier coating was done through strain-controlled fatigue tests on test specimens. Nickel coating qualification for nominal thickness carried out. Strain cycling test on specimens is a better method to qualify the coating integrity as proto qualification takes a lot of time to realise and testing. Specimen level tests give result with less time and comparable with operating condition of actual engine. Coating integrity can be examined after each stage of testing as it progressed. The stress-strain curve clearly reveals/indicates the crack formation in coating. Since cracks and peeling of coating observed at the beginning of testing, coating parameters were modified to improve ductility of coating by reducing its hardness. Specimens prepared with improved coating parameters. Tests were done to qualify the modified coating. It is observed from the tests that no coating peeling observed on modified coating for tensile as well as compressive strain testing. Thermal barrier coating in Semi-cryogenic engine is qualified through strain-controlled fatigue tests with specimen level testing. Based on the test results, reusability of engine is ensured for the designed thermal barrier coating. Acknowledgements The authors gratefully acknowledge the academic selection committee of LPSC/ISRO for giving permission for presenting this paper in ICONS 2023. We acknowledge the continuous motivation and encouragement given by Shri. Kodati Srinivas and Shri. Viswanath for completing this technical paper. Thanks, are also due to Director, LPSC for permitting to publish this paper. References ASTM E606, Standard practice for strain-controlled fatigue testing, 2004.