Fiber Laser Remelting and Surface Hardening of a Nickel-based Superalloy

In some specific industrial applications, employing Nickel based super-alloy components, a surface enhancement of product tribological properties is required. In this work, a recasting surface treatment (Soft Hardening) that would produce a slight increase in micro-hardness, in a localized and pre-defined zone, thus enhancing the mechanical properties of the surface, was performed. A Diode Laser, Fiber Active, Ytterbium doped, λ 1070 nm, with power variable in the range 400W -4 kW and an integrating segmented mirror, which produces an integrated laser beam (in a knife blade or rectangle), as well as a laser intensity homogenization and which was of interest to a depth of fusion, in the range 0.2 to 1.0 mm, were used. Different laser working parameters were tested. Remelted tracks, having a width 8 mm, were characterized in terms of surface visual inspection, morphology, metallographic examination as well as longitudinal and transverse micro-hardness. Moreover, a comparison was performed between properties of the remelted material and the base alloy. Laser Efficiency was also evaluated both in terms of Specific Molten Volume [mm3/s] and in Dau Unit [mm3/kJ], giving some interesting considerations vs laser power and working speed.