Fatigue tests of un-HIP'ed γ-TiAl engine valves for motorcycles

This paper presents some fatigue test results on motorcycle valves obtained by permanent-mould cast γ-TiAl alloy, which is an excellent alternative material for engine valves because of its low density and elevated temperature strength. Since the production and machining of γ-TiAl valves are very expensive, particular care was paid to meeting reliability requirements while trying to reduce costs. The development of high quality low-cost γ-TiAl alloy engine valves was obtained without performing a hot isostatic pressing (HIP) process. The valves were mounted onto an actual motorcycle engine and a racing-type fatigue test was then positively overcome. A contribution to the evaluation of the effect of the intrinsic defects that are typical of centrifugal mould technology on the fatigue behaviour of castings was also given.