Experimental study of WC–Co cemented carbide air impact rotary drill teeth based on failure analysis

Abstract

Air impact rotary drilling technology is applied widely in the oil drilling industry; however, bit tooth damage results in reduced bit life and low efficiency rock breaking thereby limiting the popularity and application of air percussion drilling technology. Tooth failure analysis showed that the main failure modes include wear of the middle tooth and fracture and shedding in the side tooth. Reasons for failure include the poor wear resistance and impact toughness of WC–Co carbides, which cannot withstand harsh downhole working environments. An experimental study of WC–Co carbides was performed to attempt to extend bit life. Inhibitor vanadium carbide (VC) and chromium carbide (Cr3C2) (ratio 1:3) were doped into WC–Co cemented carbide to prepare a sample WC–8%Co–0.2%VC–0.6%Cr3C2 using high-energy ball milling, molding, low-pressure sintering, and grain growth inhibition. The properties of different WC carbide grain sizes, such as the hardness, wear area, wear amount, tooth impact cracking time, and microstructure features, were analyzed to measure the wear resistance and impact toughness of carbide. Fine-grain carbide was found to exhibit the best abrasion resistance, which is suitable for the middle tooth. Coarse-grain carbide displays optimized impact toughness, which is suitable for the side tooth. Ultrafine cemented carbide with excellent wear resistance and anti-impact toughness is suitable for the middle and the side tooth. In this way, the impact and abrasion resistance of the tooth can be improved significantly and the bit life increased.