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

Ring-rolling has proven notoriously difficult to model, control, and optimise accurately. We have studied a multi-objective optimisation for the manufacturability of aeroengine 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 degrees C at strain rates between 0.1 /s and 0.001 /s, whilst enduring a good formability between 850 to 950 degrees C and 1050 to 1100 degrees 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.