Usage of continuous cooling transformation (CCT) diagrams for laser and small-scale induction hardening

Abstract

Using standard continuous cooling transform (CCT) diagrams for finding hardness of surfaces obtained by laser or small-size induction hardening is discussed. Their misuse may lead to differences between the values obtained from the model and experimental data because unlike hardening of large surfaces, the produced heat is mostly transferred away not by convection to the environment, but mainly by conduction to the interior of the metal material at a very high rate (at the level of many hundred Kelvins per second). The paper explains the details and offers a methodology of suppressing errors based on a combination of theoretical and experimental approaches. The methodology is illustrated with an example.