Residual Stress and Distortion during Quench Hardening of Steels: A Review

Quench hardening is a widely used heat treatment process for achieving better mechanical properties in carbon steels. However, when high quench-sensitivity steel components having thin sections are quenched, they may get distorted due to thermal and phase transformation stresses. Appropriate steps have to be taken to minimize residual stresses and distortion during quenching operation in the heat-treating industry. Many factors such as quenchant type, quench severity, quenching process variables, the geometry of the component, and material properties significantly affect the evolution of residual stresses. The heat transfer from the metal surface to the quench medium is the critical physical phenomenon that drives the microstructure evolution and residual stresses during quenching. The nonuniformity in heat transfer between the heated metal and the quench medium is the key source of residual stress development in the quenched material. Modeling and simulation of the quenching process can predict the residual stress distribution in the quenched sample and the evolution of quench cracks and component failure. Optimizing quenching process conditions and selecting appropriate quenchants minimize residual stresses and distortion. One of the requirements for improving the accuracy of simulation models is the use of reliable spatiotemporal heat transfer boundary conditions. The present review addresses the evolution of residual stresses during quenching, factors affecting residual stresses such as geometry and section thickness of the quenched part, cooling uniformity, quenchant selection, and the interrelation between heat transfer and residual stresses. The methods to minimize residual stress and distortion in quenched parts are discussed.