Structure-property processparameters correlation of laser surface melted inconel 718 superalloy

This investigation aims at improving wear, erosion, and corrosion resistance properties (in 3.56 wt% NaCl solution) of Inconel 718 by laser surface melting (LSM) using a 6 kW diode laser with power varying from 900 W to 1800 W and scan speed ranging from 20 mm/s to 80 mm/s, as the two main process parameters. The melt zone depth due to LSM varies from 372.24 to 1471.67 μm, showing significant grain refinement and improvement of surface microhardness from 297 to 341 VHN than that of as-received Inconel 718 (250 VHN). Microstructural and phase evolution following LSM was investigated in detail by scanning electron microscopy, energy dispersive spectroscopy, orientation imaging microscopy, and X-ray diffraction analysis. LSM results in a superior fretting wear resistance against the WC indenter and erosion resistance as evaluated by air jet erosion testing against alumina particles injected at a velocity of 100 m/s onto Inconel 718 after LSM. The corrosion resistance property following LSM is improved in terms of decrease in corrosion rate to 0.0002 mm/year as compared to 0.31 mm/year of as-received Inconel 718. The mechanism of corrosion has been established through a detailed post-corrosion microstructural analysis. Finally, statistical analysis by Taguchi methods suggests that 900 W of incident power and 20 mm/s of scan speed offer the optimum condition of LSM to achieve combined improvement of hardness and resistance to wear, erosion and corrosion for Inconel 718 substrate.