Effects of MoS₂ on the matrix performance of hot-pressed Fe-based diamond drill bit

Diamond drill bit is a common rock breaking tool in various exploration works, but the diamond in drill bit has poor thermal stability. As heat is constantly generated during the drilling process, the self-cooling of diamond drill bit under the condition of drought and water shortage is very important to improve the drilling efficiency. In order to decrease the friction coefficient between bit matrix and rock interface under dry drilling condition and reduce the thermal damage of diamond during drilling, molybdenum disulfide (MoS₂) was added into the Fe-based diamond bit matrix, and research was performed for the effects of MoS₂ content on the relative density, Rockwell hardness and flexure strength of Fe-based bit matrix, as well as the wear loss and friction coefficient during the dry grinding with white corundum grinding wheel. Besides, the morphology and phase composition on the fracture and surface of the specimens after flexure strength test and the friction-wear test were analyzed by the test instruments such as scanning electron microscope (SEM) and the energy dispersive spectrometer (EDS). The test results show that the relative density of Fe-based matrix has little relationship with MoS₂ content within the test range, but the relative density of Fe-based matrix containing MoS₂ is increased by about 2.5% to more than 98% compared with the Fe-based matrix without MoS₂. The Rockwell hardness of Fe-based matrix increases at first and then decreases with the increasing of MoS₂ content, and the HRB value is up to 101.3 at the MoS₂ volume fraction of 8%. The flexural strength of Fe-based matrix also increases at first and then decreases with the increasing of MoS₂ content, and the flexural strength is maximized to 1 140 MPa at the MoS₂ volume fraction of 2%. The wear loss of Fe-based matrix decreases at first and then increases with the increasing of MoS₂ content, and the wear loss is minimized to 0.376 g at the MoS₂ volume fraction of 4%. The friction coefficient between the Fe-based matrix and rock interface decreases gradually with the increasing of MoS₂ content, and the minimum friction coefficient is 0.325 at the MoS₂ volume fraction of 10%. The morphology and phase analysis of the fracture of broken specimen after flexural strength test shows that the continuity of Fe-based matrix microstructure is decreased with the addition of MoS₂. Further, the morphology analysis of specimen after friction-wear test indicates that the adhesive wear and plastic deformation during frictional wear are declined with the addition of MoS₂. Generally, the research results lay a theoretical foundation for reducing diamond wear and thermal damage, increasing the wear resistance of matrix, and prolonging the bit life under dry drilling conditions.