Aluminizing for TiAl turbocharger rotor by reduced pressure metal-organic chemical vapor deposition (RPMOCVD) and the efficiency of its oxidation resistance

A complex-shaped TiAl turbine rotor has been uniformly aluminized by a metal-organic chemical vapor deposition under reduced pressure (RPMOCVD), and a thick TiAl 3 layer, which affects the oxidation resistance, can be formed on the surface by subsequent heat treatment. The oxidation resistance has been studied with an oxidation test at 1173 K for 760 ks in static air. The microstructure has been investigated by SEM, EPMA, AES, and XRD. A heat treatment at above 933 K, which is the melting point of Al, is required to enhance the oxidation resistance of TiAl. With increasing the surface roughness of TiAl, the formation of TiAl 3 increases, and consequently the oxidation resistance is more improved.