Experimental investigation of laser surface processing of flexure silicon nitride ceramic

Abstract

A continuous wave carbon dioxide (CO 2) laser (λ=10.6 μm) was employed to treat the surface of Si 3N 4 MOR (modulus of rupture) bars. The effects of the CO 2 laser process on physical and mechanical properties of ground Si 3N 4 samples were investigated. Scanning electron microscopy (SEM) analysis shows that the area occupied by cavities and fracture is decreased by about 49.4% after laser treatments. Cross-sectional metallography results indicate that the secondary YSiAION phase in the Si 3N 4 ceramic is softened/melted and flowed into the defects. Four-point bending tests show that the flexural strength of the treated samples is improved to 10.9%. Fractographic analysis show that the fracture origins move from the surface to subsurface. It is concluded that laser surface processing have significant effects on fracture behavior of flexure Si 3N 4 ceramic.