Effect of CaF2 and hBN on the mechanical and tribological properties of Fe-based impregnated diamond bit matrix

Two high-temperature solid lubricants, CaF2 and hBN, were added respectively into Fe-based impregnated diamond bit matrix to fabricate self-lubricating specimens of various lubricant contents by powder metallurgy method. Mechanical and tribological tests were performed on the specimens to investigate the relationship between specimen properties and lubricant content. The microstructure of the cross sections and the morphology of the worn surfaces of the specimens were analyzed using scanning electron microscopy (SEM). The results showed that the increase in solid lubricant content had a general weakening effect on the mechanical properties of the specimens, while such effect of CaF2 was less significant than that of hBN. The hardness of CaF2 specimens was found increasing slightly with CaF2 content. Improved lubricity on the sliding surfaces was observed, while the wear resistance of the two specimens behaved differently. SEM analysis showed different microstructures of the two specimens, and improved wear condition for the CaF2 specimen. However, the worn surface of the hBN specimen was found deteriorated.