Microstructure and mechanical properties of Hastelloy-X produced by selective laser melting

Abstract

The microstructure including defects and mechanical properties of as-deposited and heat treated (HT) Hastelloy-X manufactured by selective laser melting (SLM) technology were studied, in order to apply this technique into the manufacturing of gas turbine components. The processing parameters, including scan speed, laser power, scan spacing, and linear energy density were optimized to obtain less porosity. Heat treatment at different temperatures and times was executed to modify the microstructure and reduce the residual stress. When the linear laser energy density increased (>0.12 J/mm), the porosity decreased to ∼0.5 %. By decreasing scan spacing to 0.06 mm, the porosity was further decreased to 0.2 %. With increased HT temperature, the microstructure changed from columnar grains through partial recrystallized grains to fully recrystallized coarsened equiaxed grains. Hardness decreased with increasing HT temperature and time in the HT conditions mainly due to grain coarsening and carbide reduction.