High temperature oxidation behavior of IN738LC alloy formed by selective laser melting

The high temperature oxidation behavior of selective laser melting processed IN738LC alloy at different temperatures was studied using isothermal oxidation testing. The phase composition and oxide layer morphology of the oxidation products under various temperature conditions were characterized by X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and the oxidation mechanism was discussed. The results reveal that the oxidation kinetic curves of the deposited samples at 900 and 1000 °C show parabolic law, and the oxidation rate constants kp are 2.54 × 10–4 and 7.68 × 10–4mg2/cm4·h, respectively, where the oxidation products at different temperatures are composed of Al2O3, Cr2O3, and TiO2, which meet the complete oxidation resistance level. Element Cr preferentially oxidizes to produce Cr2O3 during the initial oxidation, Ti atoms at the interface extend the diffusion to the surface of the sample through the Cr2O3 layer to produce TiO2, while the Al atoms rapidly diffuse along the fine columnar grain boundaries toward the oxide–metal interface and finally form a dense Al2O3 layer. The holes formed under the oxide film at 1000 °C will reduce the adhesion between the oxide layer and the substrate, meanwhile adversely affecting the oxidation resistance of the sample.