Validation of thermal-kinetic-diffusion model for arc plasma surface hardening of steel

Abstract

Realistic analysis of the surface hardening pocesses during an arc plasma torch application indicates that the events taking place during a plasma torch pass should be properly looked at as a thermal-kinetic-diffusion problem. Arbitrary separation of these components may lead to erroneous evaluation of the variables and parameters that characterise the process. Consequently, a complex finite element model, which describes elementary processes of gas-solid surface interaction by the method of molecular gas dynamics, connects the transfer processes between gaseous and solid phases and takes into consideration thermal and diffusion events in the steel, has been developed. The adequacy of the mathematical model was substantiated by comparing model predictions to measurements made during surface hardening using an arc nitrogen plasma torch. It was proved that the approach gives the possibility to compute with sufficient accuracy the transient distributions of temperature and concentration fields in the steel surface layer during surface hardening using high-enthalpy gas flux.