Hot working of platinum group metal-modified Ni-base superalloys for thermal protection system applications

Platinum group metal-modified nickel-base superalloys are being investigated for use in thin gage applications, such as thermal protection systems, due to their strength and inherent oxidation resistance at temperatures in excess of 1000 °C. This paper summarizes deformation behavior and microstructure evolution during multi-hit hot forging and subsequent hot rolling of an experimental two phase γ-Ni + γ′-Ni3Al alloy with a composition of Ni–15Al–5Cr–3Pt–2Ir–0.3Hf (atomic %) with C, B, and Zr additions for grain-boundary refinement and strengthening. The feasibility of hot rolling this material to a final thickness of 250 μm and obtaining a nearly fully recrystallized microstructure was demonstrated. However, an anomalous grain-growth behavior was also observed at the surface in the intermediate and final rolled product.