Assisted nitriding of Inconel alloy: microstructural analysis

Laser gas assisted treatment of pre-prepared Inconel 625 surface is carried out. A carbon film accommodating 5% TiC particles is formed at the surface prior to laser treatment process. The presence of carbon film hosts uniformly distributed TiC particles at the surface and enhances the absorption of incident laser beam. Metallurgical and morphological changes in the laser treated layer are examined using electron scanning microscope, energy dispersive spectroscopy and X-ray diffraction. The microhardness and the residual stress formed at the laser treated surface are measured. The X-ray diffraction technique is incorporated to measure the residual stress at the treated surface. It is found that laser treated surface is free from asperities including cavities, pores, and microcracks. Laser treated layer is almost 50 μm thick and it extends uniformly below the surface. The residual stress measured is on the order of 500 MPa.