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 VRR samples, HSR samples with a small axial size show a uniform temperature distribution and satisfactory microstructures within a certain range of dimensions as well as the expected phase composition; furthermore, 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.