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  • A study on developing proce...
    Jha, Arkajyoti; Shukla, Shivam; Choudhary, Amit; Manoharan, Ramji; Muvvala, Gopinath

    Optics & laser technology/Optics and Laser Technology, January 2023, 2023-01-00, Volume: 157
    Journal Article

    •Laser surface remelting of Inconel 718 is carried out.•Correlation between scan speed, cooling rate and microstructure is reported.•Process map based on cooling rate to generate preferred microstructure is developed.•Higher cooling rates resulted in decreased elemental segregation in Inconel 718.•Higher cooling rates resulted in improved performance of remelted samples. In the area of laser material processing, laser surface remelting has been found to be an effective method of improving surface properties such as hardness, wear, and corrosion resistance. However, the scale of improvement depends on the evolving microstructure and phases, which depend on the cooling rates. Therefore, in the present study, laser surface remelting of Inconel 718 was carried out and a process-structure–property relationship with respect to the cooling rates has been developed. During the laser surface remelting process, the molten pool thermal history i.e. cooling rate, molten pool lifetime, and solidification shelf time is monitored and estimated using an IR pyrometer. The evolution of microstructure is later correlated with these parameters. With an increase in scan speed, the cooling rate is found to increase resulting in transformation of microstructure from equiaxed grains to columnar epitaxial growth. Based on the results obtained, a process map is proposed to establish a particular type of microstructure with respect to the cooling rate. Further, the effect of cooling rate and microstructure on the surface hardness and specific wear rate has also been investigated. Both surface hardness and specific wear rate got reduced with decreasing cooling rate at a slower scan speed due to grain coarsening and an increase in elemental segregation or Laves phase formation.