Influence of drilling technology on wear evolution of impregnated diamond bits

Abstract

Diamond exposed on the surface of an impregnated diamond bit (IDB) is the key to breaking rock. The exposure conditions of the diamond affect the drilling efficiency and life of the bit. However, scant attention has been directed towards investigating the diamond exposure mechanism of IDBs, particularly under varying drilling process conditions. In this study, drilling experiments were conducted on granite under rotary and rotary-percussive drilling conditions using a self-developed drilling test platform. The evolution of diamond emergence on the surface of the IDB under two drilling technology conditions was evaluated; the typical characteristics of diamond wear and their causes were discussed. The results indicate that under rotary drilling conditions, the primary evolution process of diamond on a slippery IDB surface follows the sequence of Emerging→Whole→Blunt (Flat). The exposed diamond tends to be predominantly blunt and fractured, and a slippery IDB cannot be resharpened by increasing the weight-on-bit. The evolution process of a diamond under rotary-percussive drilling conditions encompasses Emerging→Whole→Fractured→Pull out, and the diamond on the surface of the bit is primarily fractured. Diamond emerges from the matrix in the form of points, lines, and planes, with different emergence states affecting its wear and failure modes. The main form of wear in diamonds is mechanical wear, which is dominated by abrasive and fatigue wear. The proportion of fractured diamonds was notably higher under rotary-percussive conditions than in rotary drilling conditions. The tail of the diamond under rotary-percussive drilling conditions was shorter than that under rotary drilling conditions. The impact effect in rotary-percussive drilling enhances the bit-rock contact, facilitating matrix wear and diamond emergence. These results provide valuable insight for optimizing the IDB design and refining drilling technology.