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High temperature coating study to reduce contact stress damage of ceramics: Final report. [ZrO/sub 2/ coatings on Si/sub 3/N/sub 4/ and SiC against contact stress]

Technical Report ·
OSTI ID:6545685
Si/sub 3/N/sub 4/ and SiC are susceptible to contact stress damage at ceramic component interfaces in gas turbine engines. Objective was to develop adherent coating compositions and procedures that will improve contact-stress damage resistance of Si/sub 3/N/sub 4/ and SiC. Yttria (Y/sub 2/O/sub 3/) stabilized zirconia (ZrO/sub 2/) coatings were applied by electron beam-physical vapor deposition (EB-PVD) to three substrate materials: reaction bonded Si/sub 3/N/sub 4/ (RBSN), sintered Si/sub 3/N/sub 4/, and sintered SiC (SSC). Several controlled substrate pretreatments (both mechanical and chemical) were used to aid in obtaining a better understanding of the mechanisms of coating adherence. Each coating/substrate system was evaluated for coating adherence before and after oxidation exposure. The coating/substrate interfaces were evaluated for microstructural characteristics. Pretreatment and coating approaches projected to improve coating adherence were selected. Specimens were prepared to evaluate the coating adherence before and after oxidation exposure. The systems exhibiting the best coating adherence after oxidation exposure were identified. Additional specimens for each of these systems were prepared for analysis of the coating thermal spall resistance, friction, and contact damage resistance. The friction and contact damage resistance of uncoated RBSN, SSN, and SSC were also evaluated.
Research Organization:
Garrett Turbine Engine Co., Phoenix, AZ (USA); Oak Ridge National Lab., TN (USA)
DOE Contract Number:
AC05-84OR21400
OSTI ID:
6545685
Report Number(s):
ORNL/Sub-84-47992/1; ON: DE87009801
Country of Publication:
United States
Language:
English