WC-Co cemented carbide has excellent cutting performance, which is a potential tool material. But when used for cutting ultra-high strength and high hardness materials, the machining accuracy and service life of the tool are significantly reduced. It was used to cut still the challenges to be solved, which led to the development of coated tools. Graphene is a potential coating material for cemented carbide cutting tools due to its excellent mechanical properties. In this paper, molecular dynamics (MD) was applied to simulate the deposition of nickel transition layer and high-temperature catalytic growth of graphene in cemented carbide. The physical vapor deposition method was used to simulate the Ni and C atomic deposition and high temperature annealing processes, and a combination of potential functions was applied to simulate the two deposition processes without interruption. The effects of deposition temperature and incident energy on the growth of graphene were analyzed. The healing mechanism of nickel-based catalytic defective graphene under high-temperature annealing was explored in detail.
Simulation Discovery：At the deposition temperature of 1100 K, the coverage of graphene is higher and the microstructure is flat. The higher temperature helps to provide enough kinetic energy of carbon atoms to overcome the potential energy barrier of nucleation, promote the migration and rearrangement of carbon atoms, and reduce graphene growth defects. Too high temperature leads to the formation of multilayered reticulation and disordered structure by carbon atoms continuously stacking up at the deposited carbon rings, which causes a low coverage rate of graphene. The increase of incident energy helps to reduce the vacancy defects in the film, but too high energy leads to poor continuity of the film, agglomeration, the stacking effect of carbon atoms and the tendency of epitaxial growth are more obvious. When the incident energy is 1 eV, the surface roughness of the film is lower, and more monolayer graphene can be grown. During annealing at 1100 K, the carbon film simultaneously underwent dissolution and nucleation in the Ni transition layer, and the nickel transition layer catalytic defect graphene healed. The graphene film became more uniform, and the number of hexagonal carbon rings increased. Appropriate high-temperature annealing facilitates the repair and reconstruction of defective carbon rings and the rearrangement of carbon chains into rings. Therefore, a high quality graphene coating was prepared after graphene deposition/ annealing at 1100 K and incident energy of 1 eV. The simulation results provide reference for the preparation of cemented carbide graphene coated tools.