Heat-resistant cast gamma-TiAl alloy with high niobium addition for passenger vehicle turbochargers

The development of a heat-resistant cast TiAl alloy for turbine wheels in commercial passenger vehicle turbochargers is reviewed. High concentration of Nb is effective in securing the antioxidation resistance and high-temperature strength, both required for this application, and the appropriate Nb concentration is 7 at.%. Furthermore, minute additions of Cr, Si, and Ni also bring about improvements in properties. The anti-oxidation resistance and high-temperature strength of the turbine wheel material made of the developed alloy are far superior to conventional TiAl alloys with low Nb, and the effect of the high Nb concentration is clearly demonstrated. Also, as a result of engine endurance testing, satisfactory durability was confirmed in the actual usage environment. (AU)