Transient micro-liquid phase HIP sintering of powder metallurgy superalloys achieved by a binary composition-splitting strategy

The preparation of powder metallurgy superalloys faces a tough dilemma. Hot isostatic pressing (HIP) achieves near-net-shaping but suffers from prior particle boundary (PPB) defects, while subsequent hot deformation eliminates PPB defects but loses the near-net-shaping advantage. This paper proposes a novel transient micro-liquid phase HIP sintering method based on a binary composition-splitting strategy to get rid of the dilemma. The composition of FGH4096 was split through machine learning into a low-melting component and a high-melting component. The mixed pre-alloyed powder of these two components and the single FGH4096 pre-alloyed powder were respectively sintered. These sintering processes were carried out under the same parameters (1240 °C, 120 MPa, 2 h). The result demonstrates that the novel strategy prevented the PPB defects as micro-liquid phase separate oxides from the surface of high-melting particles. The semi-continuous bulk TiC particles along the PPBs were transformed into discrete granular TiC along the grain boundaries and within the grains. The tensile strength of the superalloys prepared by the novel strategy at 25 °C, 650 °C, and 750 °C was increased by 3.16%, 12.79% and 6.55% respectively. The fatigue crack growth life at 650 °C with a stress ratio of 0.05 was increased by 27.5%. These properties are equivalent to those of the HIP sintered + hot-deformed superalloy.