Effect of CoO–NiO additives on the microstructure and mechanical properties of microcrystalline corundum abrasives with in-situ formed needle-shaped LaAl11O18

Abstract

It is always challenging to synthesize corundum abrasives with high strength and toughness. In this study, pure α-Al2O3/LaAl11O18 dual-phase corundum abrasives were synthesized by the sol-gel method using pseudo-boehmite as the raw material and CoO–NiO binary additives as a sintering aid. By regulating the molar ratio of CoO and NiO in the sintering additives, dense and fine corundum abrasives were prepared at a low temperature of 1400 °C. We show that the addition of CoO–NiO additives can effectively prevent the abnormal growth of α-Al2O3 grains and facilitate the formation of LaAl11O18 s-particles between α-Al2O3 grain boundaries, resulting in final corundum abrasives consisting of equiaxed α-Al2O3 and needle-shaped LaAl11O18 grains. Moreover, the presence of the needle-shaped LaAl11O18 phase promotes the fracture toughness of corundum abrasives, and the high density of corundum abrasives also makes them retain a relatively higher hardness and strength. When the molar ratio of sintering additive (n (CoO)/n (NiO)) reaches 1: 1, the single-particle strength, Vickers hardness, fracture toughness, and maximum density of our synthetic corundum abrasives are 53.4 N, 18.9 GPa, 4.53 MPa m1/2 and 3.94 g cm−3, respectively. The process route suggested in this study is expected to guide the low-temperature synthesis of corundum abrasives with well-rounded mechanical properties.