Effect of Ti and Al Contents on Sulfidation Resistance of Nickel-base Superalloy at 873K

Abstract

Sulfidation properties of the alloys that include Ti of 1.5 to 2.0mass% and Al of 2.0 to 3.0mass% with basic composition of AISI 685, which is used as a rotor material of FCC power recovery turbine, were investigated at 873K in an atmosphere of P_S2=10^-0.5 and P_O2=10^-18.5Pa. Sulfidation amount was decreased with increasing the Al content in the alloys of including the same level of Ti. The 1.5Ti-3.0Al, 2.0Ti-3.0Al and 1.5Ti-3.5Al alloys (mass%) showed the mass gain and scale thickness less than half of AISI 685. This is due to the diffusion control of metal ions and gases by the Al-rich oxide and/or sulfide in the innermost scale layer.