Influence of pressure on the phase transformation and the precipitation kinetics of high-alloyed steel - experiment and simulation

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The goal of this project is to study the influence of high isostatic pressure on phase transformation behaviours of martensitic steels and duplex stainless steels and to deduce positive aspects for the heat treatment under pressure during rapid cooling. A newly developed hot isostatic pressing unit with integrated rapid cooling system, which works with a gas pressure up to 200 MPa, allows the research of phase transformation under relative high pressure. The influence of pressure and increased alloying element contents on the hardening of martensitic steels will be clarified. Besides experimental investigations, a material model for simulation will also be developed to quantitatively understand the influence of pressure during rapid cooling on the microstructure of real components and to predict the final shape of the heat-treated HIP component. The model will be applied to simulate the behaviours of densification during heat treatments under isostatic pressure (for example, HIP). The pressure change during the heat treatment and the precipitation behaviour will be considered as input variables in the FEM-model. This way, the prediction of the residual stress state subsequent to cooling under high pressure from HIP temperature is possible. Benefitting from this model, the method will help saving energy and numerous resources. Following the numerical study, optimal temperature and pressure profiles can be obtained, which can lead to fully dense components with a desired microstructure after the HIP process with integrated heat treatment.