Microstructure and mechanical properties of a novel high Co + W polycrystalline nickel-based blade superalloy

Abstract

A novel polycrystalline nickel-based superalloy SLZhS-1R, heavily alloyed with Co + W and intended as a structural material for turbine blades in gas turbine engines, has been studied. The initial cast superalloy was prepared by vacuum induction melting in the form of an ingot with a size of Ø 100×180 mm. Compression and tensile tests were performed for the cast condition. Before compression testing, the superalloy was subjected to homogenization and heterogenization annealing, which led to an improvement of chemical homogeneity and coagulation of γ′ precipitates. As a result, the flow stresses during compression at elevated temperatures were reduced as compared to those obtained for the as-cast condition. Before the tensile testing, the superalloy was subjected to homogenization annealing (solution treatment) followed by air cooling and ageing. This improved the chemical homogeneity and led to the formation of fine γ′ precipitates with a size in the range of 0.1-0.2 µm. The obtained mechanical properties in tension were compared with those of the typical cast superalloy ZhS6U.