Effect of scanning speed on the high-temperature oxidation resistance and mechanical properties of Inconel 625 alloys fabricated by selective laser melting

Abstract

The effect of scanning speed (600–1200 mm/s) on the high-temperature oxidation resistance and high-temperature mechanical properties of selective laser melting processed Inconel 625 samples was studied at 1000 °C, 1atm of pure oxygen and vacuum environment, respectively. The high-temperature tensile test showed that the ultimate tensile strength (UTS) of sample Ⅳ(171.31 MPa) with a scanning speed of 1050 mm/s was lower than that of sample Ⅲ(185.34 MPa) with 900 mm/s, which was related to the low proportion of (low angle grain boundaries)LAGBs and its highest density. Sample Ⅳ showed the best plasticity (14.5%) mainly due to the slip promoted by the high proportion of high angle grain boundaries (HAGBs). After oxidation for 40 h, the oxide scale of all samples consists of a Cr2O3 oxide layer and nickel-rich spinel oxide. The samples with a density of less than 99% had the worst oxidation resistance due to manufacturing defects that accelerated the inward diffusion of oxygen. When the density was larger than 99%, the oxidation performance of alloys mainly affected by their distinctive microstructure. According to thermogravimetric analysis, the sample Ⅳ exhibited the lowest parabolic oxidation rate, which could attribute to its weak <100> texture, grain refinement, and a high proportion of CSL boundaries.