Corrosion and Heat Resistant Materials. Development of High-performance TiAl Exhaust Valve.

Lightweight heat-resistant TiAl intermetallic compound has a high potential for a high performance exhaust valve material to improve power output and fuel economy by increasing engine speed and reduction in valvetrain friction. In this study, to apply TiAl to exhaust valves, alloy development, process development and evaluation of TiAl exhaust valve were carried out. A new TiAl(Ti-33.5Al-0.5Si-1Nb-0.5Cr ,mass%) with excellent oxidation, hot corrosion resistant and mechanical properties has been developed for an exhaust valve material. To manufacture TiAl exhaust valves, advanced technologies such as CLV investment casting, HIP treatment, Plasma carburization improving wear resistance of TiAl were employed. Engine tests of TiAl valves were successful. A durability test confirmed excellent high temperature performance and wear resistance of TiAl exhaust valves.