High Temperature Coating Study to Reduce Contact Stress Damage of Ceramics
Abstract
Silicon nitride (Si3N4) and silicon carbide (SiC) ceramics are susceptible to contact stress damage at ceramic component interfaces in gas turbine engines. The objective of this research program was to develop adherent coating compositions and procedures that will improve contact-stress damage resistance of Si3N4 and SiC. Yttria (Y2O3) stabilized zirconia (ZrO2) coatings were applied by electron beam - physical vapor deposition (EB-PVD) to three substrate materials: reaction bonded Si3N4 (RBSN), sintered Si3N4, 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. Based on the results, 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 speci- mens 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1987
- Accession Number
- ADA344767
Entities
People
- J. Schienle
- J. Smyth