Study on the Properties of Fe-based Impregnated Diamond Bits with CaF2

Abstract:

In order to cope with drilling challenges in mining, oil and gas industries, the self-lubricating technique in material science has been introduced into the design of hot press sintered impregnated diamond bits (IDB). Such attempt aims to endow IDB with the ability to self-lubricate, so as to reduce frictional heat, prevent diamond thermal damage and improve bit service life. This paper describes an initial design where CaF2 and hBN were selected as solid lubricant additives through optimization and experiments. They were added to Fe-based matrix to prepare two groups of self-lubricating IDB matrix specimens with different lubricant concentrations via hot press sintering. The specimens’ mechanical and tribological properties were tested by a series of testing machines, and the miniature IDB were made and bench-tested. The results show that with the increase in lubricant concentrations, both groups of specimens experienced decrease in their mechanical strengths; however, the degree of such decrease differed among two groups, with hBN group dropping more dramatically. The friction coefficients of both groups dropped significantly, and the wear rate of CaF2 group first rose and then dropped; whereas that of hBN group increased substantially. The drilling footage of CaF2 group rose slightly while hBN group decreased gradually.

Key words:diamond; bit; self-lubricating; CaF2; hBN