Interfacial Bonding Controls Friction in Diamond–Rock Contacts

Understanding friction at diamond–rock interfaces is crucial to increase the energy efficiency of drilling operations. Harder rocks usually are more difficult drill; however, poor performance often observed for polycrystalline diamond compact (PDC) bits on soft calcite-containing rocks, such as limestone. Using macroscale tribometer experiments with a tip, we show that limestone rock (mostly calcite) gives much higher coefficients compared hard granite quartz) in both humid air and aqueous environments. To uncover physicochemical mechanisms lead kinetic diamond–calcite interface, employ nonequilibrium molecular dynamics simulations (NEMD) newly developed reactive force field (ReaxFF) parameters. In NEMD simulations, calcite than quartz when water molecules included interface. We water-lubricated diamond–quartz contacts due increased interfacial bonding former. For diamond–calcite, bonds mostly form through chemisorbed trapped between tip substrate, while mainly direct tip–surface inside contacts. types, rate bond formation increases exponentially pressure, which indicative stress-augmented thermally activated process. The shown be linearly dependent number during steady-state sliding. agreement behavior suggests also controls macroscale. anticipate improved fundamental understanding provided by this study will assist development bit materials coatings minimize reducing bonding.