Modeling of the Process of Hot Isostatic Pressing of Single Crystals of Nickel-Based Superalloy Taking into Account Plastic Flow and Vacancy Diffusion

Abstract

A complex model of pore annihilation during hot isostatic pressing (HIP), which takes into account the simultaneous action of the mechanisms of material plastic flow and diffusive pore dissolution due to the emission of vacancies by the pore surface, has been proposed. The obtained mathematical equations are applied to analyze the kinetics of pore annihilation in single crystals of the nickel-based superalloy CMSX-4 during HIP used for this alloy in industry. It follows from the analysis that both mechanisms (plastic flow and vacancy diffusion) make comparable contributions to the reduction of pore volume under these conditions. As the HIP pressure increases, the contribution of plastic flow increases, while the contribution of vacancy diffusion decreases. Large pores shrink in volume mainly due to the mechanism of plastic flow, however, at the final stage of pore closure, the mechanism of vacancy diffusion is more active. To ensure reliable pore healing by the vacancy mechanism, HIP should be carried out at a moderate argon pressure in the HIP plant.