Effect of laser power on the microstructure and mechanical properties of heat treated Inconel 718 superalloy by laser solid forming

The as-deposited Inconel 718 (IN718) superalloy was fabricated by laser solid forming (LSF) method under different laser power. The microstructure and mechanical properties of IN718 superalloys were analyzed by optical microscopy (OM), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), X-ray diffraction (XRD), electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM) methods after solution and homogenization‒solution‒aging (HSA) treatment. The grains of solution treated IN718 superalloys vary with increasing laser power from 1250 W to 1400 W. The Nb and Mo rich Laves phase is found in the as-deposited IN718 superalloy while being eliminated after heat treatment. Compared with the solution treated specimens, the strength and microhardness of HSA treated IN718 superalloy have been significantly improved while the elongation decreases obviously. The specimen under laser power of 1350 W has better mechanical properties than the others. The fracture surfaces of the broken tensile IN718 superalloys exhibit mostly dimpled surfaces, indicating a transgranular ductile failure mode.