The Formation of SiC Particulates and the Effects Thereof on the Microstructural and Mechanical Properties of Laser Surface Treated AISI 304 Stainless Steel
In this work the laser surface treatment of 304 stainless steel is carried out to improve the surface properties. Prior to the laser treatment process, a carbon film containing 7% SiC particles was formed at the workpiece surface. The carbon film increases the absorption of the incident laser beam energy and accommodates uniformly SiC particles at the surface. Metallurgical and morphological changes in the laser treated layer were examined using an optical microscope, a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Microhardness was measured at the laser treated surface and residual stress formed in the laser treated layer was determined from X-ray diffractograms. It was found that the microhardness improves significantly at the laser treated surface due to the presence of SiC particles, the dense layer formed, and nitride compounds formed at the surface. It was also found that residual stress at the surface region of the laser treated layer is in the order of -480 MPa; which is compressive in nature.
Keywords: CO2 laser, AISI 304 stainless steel, SiC particles, surface treatment, metallurgy, microstructure, residual stress, microhardness