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1562 |
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Wednesday, June 04, 2008, Room 05 9:40 AM Characterization 1 Modern characterization offers a good possibility for proofing the reliability and the performance of thermal sprayed coatings |
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Thermal expansion response of thermally sprayed coating |
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Miryan Bejarano* / Center for Thermal Spray Research. Materials Science and Engineering Department
SUNY Stony Brook University, USA Alfredo Valarezo/ Center for Thermal Spray Research/ SUNY Stony Brook University, USA Andrew Gouldstone/ Center for Thermal Spray Research/ SUNY Stony Brook University, USA Sanjay Sampath/ Center for Thermal Spray Research/ SUNY Stony Brook University, USA |
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Thermal mismatch within a coating-substrate system is ubiquitous in thermal spray (TS), during processing, heat treatment and many high temperature applications. Much effort has been spent to model, measure and/or predict the resulting thermal stresses in such cases. For accurate analysis, correct values of thermal expansion parameters (e.g., CTE) are critical. Typically, usage of bulk values is a common practice, but experiments show that TS coatings behavior may deviate strongly from these, due to its unique architecture and microstructure features. In this work, we performed a systematic study of expansion behavior, across a wide range of TS materials and processes (APS, HVOF-DJ-JP and -JK). Using a horizontal differential dilatometer, coatings were thermally cycled, with dimensional changes recorded in each heating and cooling stage. Results were analyzed in the context of 'reversible' aspects (e.g., anisotropy, texture) and 'irreversible' aspects (e.g. phase changes, oxidation, sintering, cracking). In all cases, coatings were sprayed under diagnostics, also allowing correlation of expansion behavior with initial in-flight particle state. |