Effect of Al2O3/YSZ microstructures on wear and mechanical properties of cutting inserts

Wear and mechanical properties of ceramic cutting inserts produced from Al2O3/yttria stabilized zirconia (YSZ) system has been investigated. The YSZ compositions were varied from 0 wt% to 100 wt%. Each Al2O3 and YSZ composition was mixed, uniaxially pressed into rhombic 80 degrees cutting inserts and sintered at 1600 degrees C for 4 h in pressureless condition. Study on the effect of the microstructure of the inserts on the mechanical and physical properties such as nose wear, Vickers hardness and fracture toughness has been carried out. Mild steel (AISI 1018) was used as the workpiece in the machining tests using the cutting inserts. The results show that 20 wt% of YSZ produced the minimum wear area. When the amount of YSZ was increased from 20 wt% to 100 wt%, the wear area also increased from 0.039 mm(2) to 0.182 mm(2). However, the Vickers hardness of the inserts decreased with the increase of YSZ, while the fracture toughness of the cutting inserts shows a continuous increase up to 60 wt% YSZ. Above 60 wt% of YSZ, the microstructure of the polished samples started to show microcracks and formed larger grain sizes of YSZ, thus hindering the transformation toughening mechanism from functioning effectively. (C) 2008 Elsevier B.V. All rights reserved.