Temperature And Gas Field Simulation And Experimental Study In The Large-capacity HFCVD System

CVD diamond films have been deposited on the surfaces of cutting tool, drawing die, mechanical seal, bearing and electrode to lower the friction and prolong their working lifetime, due to its extremely high hardness, high wear resistance, good thermal conductivity and low friction coefficient. However,, diamond-coated goods can not mass-produce due to the small capacity of existing diamond coating equipment, which seriously restricted the further promotion and application of diamond-coated products. What’s more, the diamond films on large-area substrates can not deposited in the small-capacity HFCVD system. Hot filament chemical vapor deposition has been used widely to deposit diamond films due to its advantages such as geometric simplification, low costs and operational convenience. As the larger capacity of HFCVD equipment is, the less uniform of temperature and gas flow field of substrate. So it has important theoretical and practical significance for depositing diamond films in large-capacity HFCVD equipment that studies aimed to obtain uniform temperature and gas flow field.In this present study, the three-dimensional finite volume method coupling three types of heat transfer mechanisms(radiation, conduction, and convection) is applied to predict temperature and flow distribution on the surfaces of mechanical seals and PCB milling cutters. Then, the filament arrangement, the rotational speed of substrates and the cooling water flux are studied in order to improve the uniformity of temperature distribution on the substrates. Finally, diamond films are deposited on surfaces of seals and mills with the optimized parameters obtained from the simulation results to verify the correctness of the simulation model. The main research contents are as following:1. According to FVM method, the three-dimensional finite volume method coupling three types of heat transfer mechanisms(radiation, conduction, and convection) is established to predict temperature and gas flow distribution on the substrates. What’s more, the simulation is adopted multi reference frame(MRF) and species model to realize the rotation of substrates and mixed gas in the reactor.2. Temperature and gas flow field on the surfaces of mechanical seals in large-capacity HFCVD equipment was simulated, and the results show that temperature and gas flow field is uniform to deposit diamond films by rotating of worktable and reasonable filaments arrangement. Then, the diameter of filaments, separation of filaments, distance between filaments and substrates, cooling-water flux and the rotational speed of substrates are studied in order to improve the uniformity of temperature distribution on the substrates. What’s more, the temperature distribution on substrate in the small-capacity equipment is researched to compare with the temperature distribution in large-capacity system.3. Temperature and gas flow field on the surfaces of milling tools in large-capacity HFCVD equipment was simulated, and the results show that temperature and gas flow field are uniform to deposit diamond films by rotating of worktable and reasonable filaments arrangement. Then, the diameter of filaments, separation of filaments, distance between filaments and substrates, cooling-water flux and the rotational speed of substrates are studied in order to improve the uniformity of temperature distribution on the substrates.4. Diamond films are deposited on surfaces of seals and milling tools with the optimized parameters obtained from the simulation results to verify the correctness of the simulation model. Furthermore, the cutting performance of the diamond coated milling cutters in different place to test performance of diamond films.