Influence of thermo-cyclic loads and abrasive wear on durability of PDC cutters in high-temperature wells

Polycrystalline Diamond Compact (PDC) cutters suffer accelerated degradation in high-temperature wells due to the combined action of thermo-cyclic loading and abrasive wear. This study evaluates the influence of repeated thermal cycles (0–30 cycles between room temperature and 650 °C, 30 min hold) on the subsequent abrasive wear resistance of commercial PDC cutters using simplified laboratory methods. Wear performance was assessed via a modified pin-on-disc test against a granite counterface (120 N load, 1.2 m·s-1 velocity, 2000 m sliding distance, dry conditions). Results show a nonlinear increase in specific wear rate with the number of thermal cycles: from 1.29·10-8 mm3·(N·m)-1 (non-cycled reference) to 6.04·10-8 mm3·(N·m)-1 after 30 cycles, representing an approximately 4.7-fold rise. Post-cycling degradation manifests as edge microcracking, minor spallation, and increased frictional heating during abrasion (peak temperatures rising from ~500 °C to ~650 °C). The observed wear acceleration is attributed to differential thermal expansion stresses between diamond and cobalt binder, incipient graphitization in localized hot spots, and stress concentration at microcracks that promote grain pull-out and chipping under abrasive loading. These mechanisms create a synergistic feedback loop that significantly reduces cutter durability under conditions representative of deep, hot formations. The findings underscore the necessity for thermally stabilized PDC designs and optimized operational practices to extend bit life.