Effect of trace sulfur on the hot corrosion resistance of Ni-base single crystal superalloy

The effect of sulfur on the hot corrosion resistance of Ni-base single crystal superalloy was investigated in Na2SO4 salt at 900 °C in static air. The results indicate that the corrosion resistance of the superalloy is significantly degraded even with several ppm contents of sulfur in the alloy. High sulfur content in the alloy causes the oxide layer to bulge and significantly shortens the corrosion incubation period. The accelerated corrosion process is attributed to the outward diffusion of sulfur from the alloy promoting S segregation at the oxide/metal interface and hence favors crack premature initiation.