METAL-CERAMIC STRUCTURE GRADUALLY CHANGED IN COMPOSITION

摘要

An improved durability turbine air seal comprises a metallic substrate, a metallic bond coat on the substrate, a continuously graded metal-ceramic layer on the bond coat and an outer layer of pure ceramic. The continuously graded metal-ceramic layer consists of a ceramic material having a reduced oxygen permeability compared to the zirconia material used in the prior art and a metallic material having a high resistance to oxidation. The seal is fabricated by plasma spraying with controlled subtrate temperatures to induce in the sample a controlled strain distribution so as to make the seal resistant to failure in service. Other concepts for reducing the liability of the seal to failure by oxidation are described.