Wear Behavior in Micro and Nano-Structured WC-9Co-0.7VC Cemented Carbide Produced by Rapid Hot Press Sintering

Authors

Materials and Metallurgical Engineering Department, Iran University of Science and Technology (IUST)

Abstract

The effect of CaO on the formation of β- and γ-zirconia nanoparticles from α-zirconia was investigated and their stability evaluated via mechanical activation. α-ZrO2+8.5wt%CaO powder was milled for 2-150 hours with ball-to-powder weight ratios (BPWR) of 40:1 and 60:1. Structural evaluations were conducted using X-Ray diffraction and scanning electron microscope (SEM). Thermal analysis was carried out using Differential Scanning Calorimetry (DSC). Results showed that, γ-zirconia (with a cubic structure) was obtained by ball milling of α-ZrO2+8.5wt%CaO at room temperature. It was found that α to γ phase transformation began after two hours of milling and completed after 48 hours with a BPWR of 40:1. Moreover, the Williamson-Hall equation indicated that the particle size of α-ZrO2+8.5wt%CaO was reduced to 50 nanometers and reached its equilibrium point after 24 hours of milling and was unchanged after that. In addition, DSC analysis showed that β-zirconia and γ-zirconia were unstable in pure ZrO2 powder, while CaO addition led to the stabilization of ZrO2 as β-zirconia and γ-zirconia after ball milling.

Keywords