Development of Protective Coatings for Columbium Alloy Gas Turbine Blades

摘要

Four developmental cycles of candidate selection, screening test and evaluation were performed on coatings for columbium turbine blade airfoils and root sections. Candidate coatings included numerous fused silicide compositions, silicided sintered underlays, and fused silicides plus glass, ceramic, soft metal, and flame sprayed overlays. The first three developmental cycles employed thermogravimetric analysis, isothermal furnace tests, slow cyclic tests, thermal fatigue torch tests, ballistic impact plus furnace oxidation tests, and prestrain plus oxidation tests as screening criteria. Extensive coating and coating processing compatibility studies were carried out with the aim of preventing deleterious reactions between root and airfoil coatings and degradation of the substrate alloy mechanical properties. The program was concluded with a series of advanced simulated environmental tests and mechanical property evaluations.