Oxidation Behavior of (W, Re)-Bearing Single Crystal Nickel-Base Superalloys

Four kinds of single-crystal Ni-base superalloys (12Ta–7.5Cr–5Co–4.8Al–1.9Mo–1Ti, balance Ni in wt%) containing (0–3) wt%W and (1–4) wt%Re were cast, and oxidized at 1000 °C for up to 275 h in air. In the as-cast condition, the microsegregations of (Cr, Co, Mo, W, Re) in the dendrites and (Al, Ti, Ta) in the interdendritic regions were observed. The γ/γ′ eutectic phases formed in the interdendritic regions. The oxidation rate of the cast alloys was comparable to that of the 2nd generation alloys, displaying relatively good oxidation resistance due primarily to the formation of stable alumina and chromia on the surface. Especially, the alloy with 2 wt% W and 2 wt% Re showed the best oxidation resistance among the four alloys. Uniform oxidation occurred in the dendrite area, whereas nodular oxidation occurred in the interdendrite region. Graphic Abstract