Laser irradiation of AISI 316L stainless steel coated with Si3N4 and Ti

AISI 316L stainless steel was laser surface treated with different compositions of Si3N4 and Ti under various laser-processing parameters to improve its surface hardness through reinforcement of Ti-based silicides. The laser-treated regions exhibited improved surface hardness (250–1000 HV), variations in the surface morphology (smooth and bowl like) and presence of cracks and pores depending upon the Si3N4–Ti composition and laser-processing parameters. The study shows that when the Si3N4–Ti composition is 75–25 wt% and laser parameters are 1.5 kW laser power and 1.0 m min−1 scan speed, a laser-treated region with high hardness of about 800 HV and smooth surface morphology as well as free from pores and cracks is observed. The X-ray diffractometer (XRD) and Energy-Dispersive Spectroscopy (EDS) analyses show that the laser surface-treated region has reinforced phase of Ti5Si3 and retained austenitic structure. The reinforced phase gives rise to very high hardness (or wear resistance) and also a corrosion resistance.