Wear performance and mechanical properties of 80 wt-%Al 2 O 3 /20 wt-%YSZ cutting inserts at different sintering rates and soaking times

Abstract

A series of ceramic tools with different sintering conditions based on zirconia toughened alumina (ZTA) was produced. Experiments on ZTA cutting tools with different sintering rates and soaking times were carried out. Cutting inserts with80 wt-% alumina (Al₂O₃)/20 wt-% yttria stabilised zirconia (YSZ), in which Al₂O₃ and YSZ powders are mixed, was compacted and sintered at 1600°C using solid state sintering. Mechanical and physical properties such as wear resistance, hardness HV30, fracture toughness and microstructure were analysed. Mild steel (AISI 1018) was used as the workpiece for wear resistance study. It was observed that a slower sintering rate induces better mechanical properties on the cutting tool. With increasing the sintering rate from 2 to 8°C min⁻¹, the wear area increased from 0·0443 to 0·118 mm². The hardness of the samples decreased from 1563·5 to 1313·8 HV, while the fracture toughness also decreased from 4·709 to 3·95 MPa m^1/2. For the effect of increasing sintering soaking time from 120 to 300 min, the wear area decreased from greatest (0·1939 mm²) to lowest (0·0797 mm²). Similarly, microstructural coarsening within ZTA was found to produce a fracture toughness increase from 3·95 to 6·374 MPa m^1/2. The influence of phase polymorphic transformation on the improvement of the mechanical properties is discussed.