Hot Isostatic Pressing (HIP) is widely used today to eliminate internal defects in components to achieve improved material properties like ductility and fatigue. With today’s modern HIP systems there are possibilities to incorporate more process steps into the HIP process. These process steps can be stress relief, solutionizing, quenching, ageing, tempering etc. performed in the same equipment during the same cycle which makes a very effective process route. This presentation will focus on the possibilities to perform solutionizing and quench directly in the HIP system for a typical QT steels and evaluate how HIP quench compares to water and oil quench as well as how the austenite to perlite transformation react under pressure.

Hot isostatic pressing or HIP has been used for diffusion bonding, casting densification, and powder consolidation. Continuous advances in HIP equipment design have allowed increasingly rapid cooling, recently reaching a point where true high-pressure gas quenching is now possible within the HIP unit. This capability further enables the integration of a heat treat and HIP processing. Within the heat treat industry, high pressure gas quenching has been an area of significant development, however, where typical high pressure gas quenching equipment offers quench pressures up to 15 or 20 bar, common HIP pressures are 1000 bar or higher. The ability to quench from HIP pressures appears to offer heat treat options not previously available. This paper examines ultra-high pressure gas quenching (from 1500 bar) within the HIP unit from a heat treating point of view using AISI 4140 steel, a well characterized, medium hardenability alloy, comparing the properties and microstructure of ultra-high pressure gas/HIP quenched steel to conventional water and oil quenched results.