On Optimising Ring-Rolling Manufacturability of C&W Nickel Superalloys for Aero-engine Turbine Disc

Abstract

Ring-rolling has proven notoriously difficult to model, control, and optimise accurately. We have studied a multi-objective optimisation for the manufacturability of aero-engine turbine disc by integrating (1) geometrical constraint, (2) alloy design, and (3) process parameters. Accurate computational models based on accurate experimentation which allow for knowledge-based choice of the manufacturing variables represent an important step towards an optimised ring-rolling process. Optimal ring-rolling formability is found by (1) minimising the adiabatic heating effect and stress intensity feature (geometrical constraint); (2) developing a new C&W M647 nickel-based superalloy with an optimal ring-rolling formability at temperatures from 950 to 1050∘C at strain rates between 0.1 /s and 0.001 /s, whilst enduring a good formability between 850 to 950∘C and 1050 to 1100∘C over strain rates between 10/s and 0.1/s (alloy design); and (3) implementing a feedback framework to control and optimise the process parameters. Within the optimal regime, mechanical behaviour is characterised by stable and homogeneous deformation. The findings are used to construct a processing map, on which the dominant deformation mechanisms are identified and used to develop a high-fidelity numerical tool, deducing a range of safe operating windows for an optimal crack-free result using a reduced processing time. The results indicate a major improvement of ring-rolling manufacturability by cutting more than 80 per cent of processing time whilst maintaining a crack-free condition.