High-temperature oxidation behavior of a novel γ′-strengthened superalloy manufactured by laser-beam powder bed fusion: Effect of post-heat treatment

This study systematically researched the high-temperature oxidation behavior of a gamma '-strengthened alloy based on Haynes 230 prepared by laser-beam powder bed fusion (PBF-LB). The results indicate that the experimental alloy showed a higher oxidation resistance than Haynes 230 at 1000 degrees C. The oxidation products mainly consisted of the outmost MnCr2O4-TiO2 layer, intermediate Cr2O3 layer and inner TiO2 layer. Branched Al2O3 oxides were formed in the interior oxidation zone. Post-heat treatment can increase oxidation resistance by reducing the oxidation rates from 0.0152 mg2cm- 4h- 1 to 0.0126 mg2cm- 4h- 1. The decrease in dislocation density and the precipitation of ordered gamma' phases can slow down the short-circuit diffusion and lattice diffusion rate of oxygen, and are the main reasons for this improvement. Furthermore, the gamma' phase precipitation and dislocation density reduction can provide more sites for Cr2O3 nucleation and reduce the Cr supply required for grain growth. As a result, the Cr2O3 grains on the heat-treated sample surface were smaller.