Laser gas assisted nitriding of alumina surfaces

The laser control melting can be applied to improve the structural and tribological properties of alumina surfaces. In this case, the laser remelting provides a homogeneous structure while the assisting gas diffuses into molten layer forming the nitride compounds in the irradiated region. Since the process is rapid, local heating with controllable depth and cost effective, the laser remelting provides several advantages over the conventional surface treatment techniques. In the present study, laser melting and gas assisted nitriding of alumina pellets are carried out. Morphological and metallurgical changes after the laser treatment process are examined using scanning electron microscopy (SEM), optical microscopy and X- ray diffraction (XRD), and indentation tests. It is found that two regions are formed in the laser irradiated zone. The first region below the surface is dense and composes of alpha-Al2O3 and AlN while in the second region, which is below the first region, randomly stacked lamellae structure is observed.