Evaluation of Boride Layers on C70W2 Steel Using a New Approach to Characterization of Boride Layers

Abstract

In this study, boride layers on C70W2 steel, obtained by boronizing at temperatures ranging from 870 to 970 °C and durations from 4 to 8 h, were investigated. The characterization of the layers was carried out using a new approach based on the change in the volume fraction of the boride phase. Analysis of the change in volume fraction showed that an increase in temperature and duration resulted in thicker layers, with temperature having a greater influence. Based on the volume fraction of the boride phase, the layer is divided into compact and toothed parts. With increasing temperature, the thicknesses of both parts of the layer increased. The thickness of the toothed part was the highest after 6 h of boronizing and further prolongation of boronizing led to a decrease in the thickness. Regression equations were estimated for the prediction of the volume fraction of the boride phase, the thickness of the compact part, and that of the toothed part of the boride layer as a function of the boronizing parameters. This study has shown that characterization based on the volume fraction of the boride phase offers advantages over the conventional method based on the average thickness of the layer.