Effects and mechanisms of an alternating current field on pack boriding

An alternating current field (ACF) was applied to AISI 1045 steel samples and boriding media for enhancing pack boriding. Effects of the ACF on temperature changes of treated samples, reaction extents of boriding media, as well as on boride layers' growth and hardness distribution, were investigated for revealing mechanisms for the enhancement. A temperature rise caused by the ACF is detected, and it increases with increasing ACF current and decreases with increasing furnace soaking temperature. Reactions of boriding media are proved being intensified by the ACF. Pack boriding, in terms of boride layer thickness, is enhanced by the ACF, and the enhancement is increased with increasing the ACF current. The Vickers' hardness distribution along the boride layers depth to the substrate can be optimized by applying ACF. It is shown that the temperature rise caused by the ACF is not the main reason for enhancing boride growth and modifying layers' phases. Mechanisms for the ACF's effects are given by concerning the ACF's thermal and non-thermal functions. The non-thermal effect is more effective than the thermal effect in intensifying reactions and diffusions in pack boriding.