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

Abstract

In the processing of hard and brittle materials such as silicon nitride (𝑆𝑖 3 𝑁 4 ), machining is often accompanied by numerous shortcomings which lead to poor processing efficiency. In order to enhance the grinding efficiency of silicon nitride ceramics, the material's strength is weakened through a 355 nm nanosecond pulsed laser for generating microscale textural patterns on ceramic surfaces. This paper investigates the influence of overlap rate on the material surface and the scratching characteristics of single diamond abrasive grains 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 diminished fracture impact regions and lower acoustic emission signal values, thereby making them more suitable for machining operations under high levels of scratching force.