Study on the three-dimensional topography of the machined surface in laser-assisted machining of Si3N4 ceramics under different material removal modes

Abstract The surface topography directly impacts the component performance. However, the two-dimensional (2D) surface roughness parameters in the previous studies have been inefficient and inadequate to describe a surface. In this study, with the help of a confocal laser scanning microscope and a scanning electron microscope, the three-dimensional (3D) topography of a machined Si3N4 surface using laser assisted machining (LAM) under different material removal modes was comprehensively characterised and compared using the standard ISO 25178–2:2012 surface texture parameters. The relationship between the 3D topography parameters and service properties was analysed. LAM is effective for machining ceramics with a high hardness and high brittleness. Different material removal modes were obtained by changing the power of the laser and were inferred by comprehensively analysing the macroscopic and microscopic topography of the chips, tool wear, and machined surface. In ductile material removal mode, the surfaces are anisotropic and cutting marks are clearly visible. Decreasing the power of the laser increases the value of the height and functions parameters. Decreasing the power of the laser also decreases the value of the hybrid and feature parameters.