For hard rock drilling in coal mine, the drilling efficiency and service life of polycrystalline diamond compact bit are very low. To overcome these shortcomings, the bionic technology is applied to the design and processing of polycrystalline diamond compact bit. The bit body and polycrystalline diamond compact cutter are designed as bionic structures, and the test of the bionic polycrystalline diamond compact bit is carried out. Test results show that, when drilling in fine sandstone with hardness greater than 9, the performance of the bionic polycrystalline diamond compact bit is significantly improved. Comparing with the Φ113-mm concave polycrystalline diamond compact bit, the service life and drilling efficiency of the A-type bionic polycrystalline diamond compact bit increase by 54% and 230%, respectively, the service life and drilling efficiency of the B-type bionic polycrystalline diamond compact bit increase by 345% and 204%, respectively, which show that the bionic design of polycrystalline diamond compact bit can provide a new research idea for hard rock drilling in coal mine. Also the test results indicate that, when processing the bionic polycrystalline diamond compact cutter, the linear cutting process will cause thermal damage to the diamond layer of polycrystalline diamond compact cutter, while the cold grinding process shows higher comprehensive performance, therefore the one-time synthesis of bionic polycrystalline diamond compact cutter is the future research direction.

Fatigue fracture is the main failure form of mining drill pipe joints, which directly leads to the occurrence of drill pipe drop accidents. Based on the principle of engineering bionics, the spine structure and kinematic behavior characteristics of cheetah were studied; the bionic design and trial production of drill pipe joints were carried out. For the bionic drill pipe joint, it separates the torsion transmission function from the connection function, and when the torsion transmission function of the joint fails, the connection function is still effective, so as to achieve the effect of “breaking the bones and connecting the ribs.” The mechanical and flow field properties of the bionic drill pipe joint were analyzed. Mechanical test results showed that, for the bionic drill pipe joint, the average tensile capacity was 555.48 kN and the average torsion capacity was 8914.13 N·m, which met the mechanical performance requirements. The flow field numerical simulation results showed that, when the drilling fluid velocity field and pressure field were stable and change evenly, there is no risk of leakage. The study results can provide a new research idea for the research and development of mine drill pipe joint with long life and antidropping function.

The double-connection structure of bionic joints of mining drill pipes has solved the problem of drill drop caused by fatigue cracks. However, with low-melting-point elastic–ductile alloy filling in the bionic joint, the thread on the joint cannot be hardened by high-temperature surface hardening treatments such as quenching and nitriding, making it prone to thread gluing or excessive wear. In this paper, the feasibility of diamond-like film deposition on the surface of a bionic drill pipe thread was studied. A tungsten transition film was used to improve the thickness of the film and the interfacial bond strength between the film and the substrate. The test results show that the total thickness of the DLC film is about 3~5 μm, the roughness is less than 2 μm, the hardness of the film reaches 24.4 GPa, the friction coefficient is 0.04, and the critical load is 56 N. SEM and EDS analyses show that the tungsten film and the bionic joint thread form a metallurgical structure. The morphology of the diamond-like carbon film is uniform and dense, and there is no obvious stratification between the substrate material. The joint with a diamond-like coating treatment has a longer service life than joints receiving conventional high-temperature nitriding treatment.

In order to improve the wear resistance, impact toughness and other comprehensive properties of PDC cutter, a new type of graphene-enhanced PDC cutter was developed by taking advantage of the excellent mechanical and thermal properties of graphene. T...