Influence of powder characteristics on the microstructure and mechanical properties of HIPped CM247LC Ni superalloy

This work investigates the influence of gas atomised powder particle size and characteristics on the microstructure and mechanical properties of hot isostatically pressed (HIPped) CM247LC nickel-base superalloy powders. Three different GA powders (particle size ranges: 53-150 mu m: 0-150 mu m; 15-53 mu m) of very similar compositions were HIPped at the gamma' solvus temperature. Microstructural analysis and tensile testing were conducted on as-HIPped samples. It was found that the fine powders promote the formation of prior particle boundaries (PPBs) decorated with carbide and oxy-carbide clusters due to the higher oxygen content per weight in fine powders, which adversely affects the mechanical properties. It was also found that coarse powder particles are beneficial for minimising PPBs and increasing the twin boundaries fraction. Nonetheless, the best balance of high temperature tensile properties was in the wide range powder (0-150 mu m). The effect of particle size was further investigated by sieving the wide range powder into two particle size distributions. Tensile testing of these conditions showed that the hot ductility could be further improved by removing the very fine powder particles. Both of the sieved powders exhibited better hot ductility than the wide range powder and also outperformed the 53-150 mu m and 15-53 mu m powders. (C) 2019 The Authors. Published by Elsevier Ltd.