Effect of arsenic on the high temperature oxidation and hot shortness behaviour of copper-bearing steel

Abstract

To understand the disadvantages caused by As in Cu-bearing steels during hot working processes, high temperature oxidation and surface hot shortness characteristics were systematically investigated using thermogravimetry (TG), optical microscopy (OM), scanning electron microscopy (SEM) and Gleeble-3800 thermal/mechanical simulation system. Analyses of TG curves and the oxide scale morphologies showed that the oxidation kinetics for all steels obeyed the initial linear oxidation law and the later parabolic oxidation law at 950–1050 °C, while the kinetics presented two different stages of the linear oxidation law at 1100 and 1150 °C due to oxide scale separation. Increasing the As content from 0 to 0.15 wt.% decreased the oxidation activation energy and accelerated the oxidation degree of Cu-bearing steel. Cu + As enrichment indicated that an increase in As content induced the precipitation of a more hazardous Cu-rich liquid phase along grain boundaries by decreasing the solubility of Cu in austenite and the melting point of the Cu phase at 1050 °C. Furthermore, the degree of Cu + As enrichment became more serious with an increase in the oxidation temperature from 1000 to 1050 °C, and then decreased because of occlusion and faster back diffusion of Cu + As into the matrix at 1100 and 1150 °C. The hot compression results agreed well with the enrichment behaviour of Cu + As obtained from investigations of isothermal oxidation.