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

摘要

Sulfidation properties of the alloys that include Ti of 1.5 to 2.0 mass percent and Al of 2.0 to 3.0 mass percent with basic composition of AISI 685, which is used as a rotor material of FCC power recovery turbine, were investigated at 873 K in an atmosphere of P_S_2=10~(-0.5) and P_O_2=10~(-18.5) Pa. Sulfidation amount was decreased with increasing the Al content in the alloys of including the same level of Ti. The 1.5Ti-3.Cal, 2.0Ti-3.Cal and 1.5Ti-3.5Al alloys (mass percent) 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.