Influence of a Cr2O3 glass coating on enhancing the oxidation resistance of 20MnSiNb structural steel

In this paper, a glass protective coating containing chromium oxide deposited on a high-quality 20MnSiNb structural steel was prepared by a slurry-spraying technique at high temperature. Compared with a bare sample, the effect of the coating on the steel was investigated at a temperature range from 700 °C to 1150 °C in the air. The experimental results showed the coating had significant oxidation resistance and effective descaling ability for 20MnSiNb structure steel. The coating could enhance protective effect by 86% after heating for 60 min at 1050 °C compared with the bare sample. The formation of a dense chromium and silicon compound film on the 20MnSiNb structural steel prevented the diffusion of oxygen and iron ions. Due to the difference of the thermal expansion coefficient between the coating and the steel, the coating spalled during the cooling process, which enhanced the descaling ability significantly. The sample was characterized by XRD, SEM-EDS and TG-DTA/DSC to clarify the possible protective mechanism, which was the synergy between the glass coating and the protective film formed by the migration of chromium, preventing the diffusion of oxygen and iron ions. Because of the low cost and easy handling method, the coating has potentially applicable for reheating process of 20MnSiNb structural steel.