EROSION OF MOLD-STEEL SURFACE OXIDATION AND NITRIDING LAYERS DUE TO A DIE-CASTING ALUMINUM ALLOY

摘要

The resistance to erosion due to A356 aluminum-alloy melt of H11 die steel treated with two different surface-treatment technologies (oxidation treatment and nitriding treatment) was investigated by employing a hot-dip-aluminum (immersion) experiment. The microstructure, chemical constituents, phase compositions, heat-flux variation and activation energy were analyzed, using a scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Compared to the nitrided samples, the oxidized samples have a smaller erosion area and a lower mass loss. Moreover, the nitrided samples require lower Gibbs free energy to react with the aluminum-alloy melt. Compared to the samples with the oxidation treatment, the activation energy of the reaction between the nitrided samples and aluminum alloy is smaller. These results indicate that the H11 die steel surface-treated with oxidation tends to exhibit a better erosion resistance to aluminum-alloy melt than the steel surface-treated with nitriding.