Effects of Design/Processing Parameters on Performance of PDC Drag Cutters for Hard-Rock Drilling
by J.L. Wise and D.W. Raymond at Sandia National Laboratories
C.H. Cooley and K.E. Bertagnolli at US Synthetic Corporation
Sandia National Laboratories and U S Synthetic Corporation have jointly conducted a multifaceted, baseline experimental study to support the development of improved drag cutters for advanced drill bits. This study, which involved the production and laboratory testing of different nonstandard cutter lots, evaluated the influence of variations in selected design and processing parameters on cutter loads, wear, and durability in hard-rock environments. The focus was on drag-bit cutters that incorporated ultrahard PDC (Polycrystalline Diamond Compact) overlays (i.e., diamond tables) on tungsten carbide substrates. Parameter variations selected for the test cutters included changes in cutter geometry, material composition, and processing conditions. Geometric variables were the diamond-table thickness, the chamfer design for the cutter edge, and the diamond-table/substrate interface configuration. Material and processing variables for the diamond table were, respectively, the nominal diamond particle size and the pressure that was applied during cutter production. Complementary drop-impact, granite-log abrasion, linear cutting-force, and rotary drilling tests examined the response of cutters from each lot. A wide range of behavior was observed from lot to lot, and analyses of the test results assessed the relative merits of these lots, allowing identification of features contributing to improved cutter performance in hard-rock (e.g., geothermal) drilling applications.