Effect of milling on microstructure, mechanical properties and wear resistance of Al2O3/Ni cermets

This research investigates the effects of ball milling on microstructure, mechanical properties and tribological behavior of Al2O3/30wt%Ni cermet. For this purpose, the primary powders of alumina and pure nickel were either mixed using a turbula mixer or milled using a planetary ball mill. The mixed or milled powders were consolidated by spark plasma sintering at 1250 °C and 30 MPa, and the properties of the produced composites were investigated. The results showed that the milling process caused the formation of a layer of nickel particles on the surface of the alumina particles, which improved the sintering process. As a result of the milling, the distribution of nickel particles in the alumina matrix and the bonding quality between them improved and the microstructural porosity was also reduced. The hardness of the mixed or milled composites was measured as 576 and 858 Vickers, respectively. In addition, the friction conditions in the milled composite became more stable and its friction coefficient decreased compared to the mixed sample. The wear rate for mixed and milled composites was calculated to be 0.00414 and 0.00081 mm3/m, respectively. The results of the wear surface analysis showed that the formation of the tribo-layer plays an essential role in the wear behavior of alumina-nickel cermets.