Mechanical Performance of Heat-Treated Lean Cr-alloyed PM Steel and Predicting its Hardenability Requirements using Simulations

A lean Cr-alloy with 0.85wt.% Cr and 0.15wt.% Mo was recently introduced as a Cu-free sustainable alternative PM material. It is always necessary to ensure sufficient hardenability for a selected component and heat treatment process, and with leaner alloys more precautions are necessary. Low-pressure carburising (LPC) combined with gas quenching is preferred for carburising Cr materials, as it avoids oxidation and provides better control over case depth. However, the nature of the gas quenching process requires more alloying to achieve better hardenability compared to oil quenching. In this study to investigate the influence of alloying element on the hardenability, both Ni and graphite were varied between 0 and 2 wt.% and 0.25-0.45 wt.%, respectively for the lean Cr samples. LPC was performed after sintering, and the mechanical performance and hardenability were evaluated. In addition, using simulations, geometry aspects necessary to fulfil the hardenability requirement for high performances were explored to be able to optimise the alloying content for a given application.