Simulation of the hot isostatic pressing process

Abstract

This work, models the compaction of a dispersed body under the conditions of a hot isostatic pressing (HIP) cycle using the example of the manufacture of compacts from VZh159ID powder and Inconel alloy 718. For the research, VZh159ID powder of fraction -70 + 25 μm, bulk density of 3.77 g/cm3 (4.83 g/cm3 after tapping), fluidity of 2.3 g/s, specific surface area of 446 cm2/g, and average particle size was used according to Fisher 16 microns, as well as Inconel alloy 718 powder of fraction -315 + 25 microns, bulk density 3.84 ... 4.58 g/cm3 (4.52 ... 5.24 gcm3 after tapping), fluidity 1.58 ... 1.90 g/s, specific surface 330 ... 376 cm2/g and average particle size according to Fischer 19.0 ... 19.5 microns. Before the HIP cycle, the powder backfills underwent thermal degassing in vacuum, since powders with such a high specific surface are subject to rapid gas sorption. Gases on the surface of the powder body as a result of the HIP cycle can form non-metallic inclusions that reduce the properties of the compact. In the microstructure of compacts after HIP, there is no network of residual boundaries from granules (PPBs-Prior Particle Boundaries), which indicates an effective technology of vacuum degassing of the powder. Simulation of the compaction process was carried out according to the modernized equation of E. Ryshkevich, constants b were selected for the materials considered. The results of the experiments of interrupting the HIP cycle and data on the strength of the samples at high temperatures obtained by selective laser sintering were used as the initial data for modeling. The proposed modeling method is quite simple (does not require experiments on an interrupted HIP cycle) due to the shown possibility of experimentally determining the strength characteristics of alloys at elevated temperatures on samples obtained by selective laser sintering. The analysis of the obtained microstructures (estimation of porosity) of the samples after HIP, having different density values, shows a good agreement of the proposed model with the real process of compaction in the gasostatic extruder.