Performance of advanced turbocharger alloys and coatings at 850–950 °C in air with water vapor

Turbochargers for transportation and power generation systems are of significant interest to improve efficiency and reduce specific emissions. As exhaust temperatures continue to increase, the oxidation resistance and mechanical properties of candidate Ni-base and TiAl alloys were investigated at 850–950 °C in wet air to simulate exhaust gas. Room temperature tensile properties were measured after exposures showing some loss in ductility and strength after 500–1000 1-h thermal cycles. At 950 °C, Ti–49Al–2Nb–1Cr was more severely attacked suggesting Ni-base alloys are needed at this and higher temperatures. Selected Ni-base alloys also were aluminized via chemical vapor deposition or a low-cost slurry process and the as-deposited chemistry and microstructure are shown. Initial coating oxidation results at 950 °C in wet air are reported.