Machining of aluminium nitride ceramic with a hAJM process using SiC abrasives: Experiments and simulation

Abstract

Extreme hardness makes aluminium nitride (AlN) ceramic machining costly. Hot abrasive jet machining (hAJM) erodes a target profile by indentation of an air-hot abrasive stream comprising fine hot SiC grains for cutting AlN ceramic materials without thermal deformation. This study is intended to analyze the material removal rate (MRR) in the hAJM process of AlN ceramic. The Box-Behnken design of experiments was used to test 15 sets of machining limitations (abrasive temperature, compressed air pressure, and nozzle angle) (BBDOE). Computational fluid dynamics (CFD) modeling was used to establish a relationship between machined profile shape and erosive flow. Hot abrasives in hAJM improved material removal efficiency. SEM investigation of the machined surface indicated fracture initiation, propagation, and erodent particle embedment. Depending on the percentage concentration and mesh size of the abrasive grains, they are dispersed randomly throughout the medium. The predicted results from simulation and those obtained from experimental observation are compared to describe the relative importance of hAJM constraints. Moreover, the analysis revealed that abrasive temperature, nozzle angle, and air pressure significantly influenced the machined surface profile and material erosion. Improved hole quality, material erosion, and impact collision of abrasives were obtained under machining with the vertically positioned nozzle.