Effect of W content on oxidation resistance of experimental third generation single crystal superalloy

Abstract:

The isothermal oxidation behaviors of three kinds of experimental third generation single crystal superalloys with different tungsten contents were investigated at 1100℃ in air by X-ray diffraction (XRD), scanning election microscopy (SEM) and energy disperse X-ray analysis (EDX). The experimental results showed that three kinds of alloys approximately obeyed subparabolic rate law during oxidation of 100h at 1100℃. The mass gains of 8wt. % W-containing alloy remained higher than the mass gains of 6 wt.% and 7wt.% W-containing alloys. The oxide scale exposed at 1100℃ was consist of three layers: an outer Ni(Co)O layer, an intermediate layer mainly composed of oxides and spinels, and an inner Al2O3 layer. The γ′-free layer was formed in the base alloy. In the current alloy system, the transition of oxidation mechanism happened with increasing W content at 1100℃, therefore, it was found that the alloys with a W content less 7% exhibited relative balance between oxidation resistance and solution strength.