Experimental investigations on surface topography and scratching performance of silicon nitride ceramics ablated by nanosecond pulsed laser

In the processing of hard and brittle materials, such as silicon nitride (Si3N4) ceramics, machining process is often accompanied by numerous shortcomings which lead to poor efficiency and quality. In order to enhance the grinding efficiency of Si3N4 ceramics, the material's strength is weakened by a 355-nm nanosecond pulsed laser for generating microscale textural patterns on ceramic surfaces. This paper investigates the influence of overlapping rate on the material surface and the scratching characteristics of single diamond abrasive grain on the grooved and cratered surfaces to elucidate the material removal mechanism of the textured surface. Experimental results indicate that the time series of laser ablation depth follows fractal geometry, and the laser ablation products primarily consist of a mixture of silicon and silica. Laser-induced surface texturing facilitates a transition in the material removal mechanism from a mode dominated by plastic flow to a mixed mode involving both brittle fracture and plastic flow. In contrast to grooved surfaces, cratered surfaces demonstrate relatively diminished fracture impact regions and lower acoustic emission signal values, making them more suitable for machining operations under high levels of scratching force.