Tribological studies on laser surface melted Hastelloy C-276

Abstract

Hastelloy C-276 was laser surface melted in a nitrogen environment in order to improve the wear resistance. The metallurgical characterisation was performed using optical microscopy, scanning electron microscopy with electron dispersive spectroscopy (EDS) and X-ray diffraction analysis. At a particular laser power and scan speed combination, significant grain refinement was achieved with finely dispersed cell-like structure which improved the hardness up to 390 HV0·3. The EDS point analysis indicated nitrogen diffusion at the cost of nickel depletion. The absence of Cr₂N or CrN is a positive aspect in preserving the intrinsic corrosion characteristics of the alloy. The wear rates of the laser treated specimens were significantly lower by a factor of 2·5. Potentiodynamic polarisation corrosion test on the laser treated specimens also exhibited reduced corrosion rates compared to the base material.