Hiroyuki Kawaura

New surface treatment using shot blast for improving oxidation resistance of TiAl-base alloys

Abstract A new surface treatment using shot blasts with WO 3 powder has been developed. This has been most effective in improving the cyclic oxidation resistance of TiAl-base alloy in air and in a diesel engine exhaust gas atmosphere of up to 1223 K. This effect is attributed to the formation of an Al 2 O 3 layer in an oxidation atmosphere. The above layer is supposed to be formed as follows: Since the WO 3 powder is shot repeatedly during the surface treatment, a WO 3 layer adhering to the substrate is formed on the surface. This layer causes the preferential oxidation of aluminum at the early stage of oxidation, resulting in the formation of a sound and continuous Al 2 O 3 layer. The developed surface treatment gives the same oxidation resistance as that of nickel-base superalloy Inconel 713C up to 1223 K, and is applicable to complex-shape parts with as-cast skin surfaces, such as turbocharger wheels.