Spark plasma sintering of α/β-SiAlON ceramic end mill rods: Electro–thermal simulation, microstructure, mechanical properties, and machining performance

Spark plasma sintering (SPS) is a highly efficient method for the preparation of α/β-SiAlON ceramics. However, the rapid preparation of large-scale α/β-SiAlON ceramic components with reliable mechanical properties is difficult via SPS due to their near-insulating properties. In this study, high-performance α/β-SiAlON ceramic end mill rods with large aspect ratios were successfully prepared via SPS. Two different types of sintering processes (namely vertical-round-rod (VRR) and horizontal-square-rod (HSR) processes) were developed, and their effects on the phase composition, microstructure, mechanical properties, and machining performance of the α/β-SiAlON ceramic end mill rods were studied. The electric and temperature field distributions during sintering were studied through an electro-thermal simulation. The simulated and experimental temperature distributions are in good agreement. In contrast to the VRR samples, the HSR samples with a small axial size show a uniform temperature distribution and satisfactory microstructures within a certain range of dimensions, and the expected phase composition; furthermore, the elongated β-SiAlON grains are preferentially oriented in the direction perpendicular to the sintering pressure direction. As a result, the HSR samples exhibit better mechanical properties and machining performance than the VRR samples.