Effect Of Process Control On The Densification Of Cr-Prealloyed PM Steels Through Vacuum Sintering In Conjunction With Capsule-Free Hot Isostatic Pressing

Paper in proceeding, 2022

In this study, compacts of Cr-alloyed steel with admixed nickel (2wt.%) and graphite (0.3 wt.%), fabricated through cold isostatic pressing (CIP), were sintered in low vacuum at 1150 °C and at 1250 °C in a HIP furnace, followed by the capsule-free hot isostatic pressing (HIP) at 1150 °C in the same HIP furnace using argon at 100 MPa pressure. Microstructures of these compacts sintered at 1250 °C revealed the complete closure of interconnected porosity, after which densification to full bulk density was achieved by the final HIP stage. Hardness measurements and chemical analysis were also employed. Carbon as a reducing agent played a crucial part to reach very low oxygen content of 0.02% after sintering and HIP. This study demonstrates the possibility of achieving full density in high performance powder metallurgy (PM) steels through novel approach of CIP and in-situ vacuum sintering in combination with capsule-free HIP using a two-stage densification process.