Causes of Distortion during High Pressure Gas Quenching Process of Steel Parts

Quench hardening is a necessary process for improving the mechanical and fatigue performance of load bearing steel components, but liquid quenching can lead to large distortions. High pressure gas quenching is becoming a more popular choice, with the assumption that a slower cooling rate will lead to less distortion. While true for certain geometries, nonlinearities in distortion response can make understanding the dimensional change of a component difficult due to the inherently complex behavior during quenching. Through the use of modeling, and a specially designed coupon, the out-of-round distortion of an eccentric bore is examined for common high pressure gas quenching conditions. The causes of distortion are examined and explained using the model, with insights into why the cooling rate has a nonlinear relation with distortion.