Sputter deposition of TiC on TiAl

Abstract

Titanium aluminide, gamma-TiAl, is an advanced material developed for high temperature applications. To improve high temperature oxidation resistance of materials, various techniques have been proposed. Two prominent approaches are alloying element addition and coating. Silicon carbide, having excellent high temperature oxidation resisting characteristics, is suggested for use as coating on TiAl to promote its high temperature stability. For high temperature applications, it has been observed that SiC and titanium alloys easily form an interfacial reaction zone consisting of TiC. The direct contact between SiC and TiAl, thus, is considered undesirable when used at high temperatures. Since TiC is the reaction product between SiC and TiAl and since the CTE, coefficient of thermal expansion, of TiC, 7.5 [times] 10[sup [minus]6]/[degree]C, is between that of SiC, 4.5 [times] 10[sup [minus]6]/[degree]C, and TiAl, [approximately]10 [times] 10[sup [minus]6]/[degree]C, a TiC layer would provide a reasonable bridge between SiC and TiAl. It serves the purpose as a diffusion barrier and a functionally gradient interlayer. This study examines the application of TiC film with sputter deposition on the surface of TiAl as an intermediate layer before SiC is coated on TiAl specimens.