Experimental investigation and finite-element modeling of the short-time induction quench-and-temper process of AISI 4140

Abstract

Abstract Induction hardening is a widely used surface treatment technique that has extensively been investigated. In contrast, induction tempering with short heating times ≤ 1 s has not been investigated thoroughly, nor by experiment neither by simulations. Also, the influence of rapid tempering on the residual stresses after induction surface hardening has only been investigated superficially. Induction quench and temper experiments were performed, both with heating times ≤ 1 s. A significant change of the residual stress state was observed, leading to a shift from compressive to tensile residual stresses in the surface layer. A multiphysical FE-model for the whole quench-and-temper process has been developed and validated. A good agreement with the experiments for the relevant mechanical properties hardness and residual stress could be achieved. The recently reported transformation induced plasticity during tempering has been found to play a key role in the development of residual stresses during tempering. The simulations further indicate that conventional heat treatment leads to more favorable residual stress states after tempering to a prescribed surface hardness. By accounting for tempering processes during austenitization, the hardening simulation could be generalized to different initial states and allows for the prediction of hardness minima in the transition zone.