The Effect of the Gas Inlet on the Fluid Field During Fabricating HFCVD Diamond-Coated Cutting Tools

Abstract

In the present study, the°uid¯eld in a process of fabricating diamond coated cutting tools using the hot¯lament chemical vapor deposition (HFCVD) method is investigated using the¯nite volume method (FVM), in which the e®ects of the inlet height, gas initial velocity, inlet radius and arrangement are illustrated in terms of the gas velocity magnitude and vector distribution near thē laments and the°ute surface of cutting tools. In the simulations, the coupling e®ect of the temperature and the gas¯eld is also considered by simultaneously calculating the temperature distribution. The simulation results suggest that either shortening the distance between the gas inlet and laments, or increasing the gas initial velocity is helpful for the reactive gas arriving at¯laments surface and being dissociated. Furthermore, increasing the inlet area is able to signi¯cantly increase the velocity of gas¯eld around the¯laments, as well as produce a much more uniform gas velocitȳ eld. Based on this conclusion, two novel multi-inlets setups are proposed to further improve the generated gas¯eld and the simulation results show that the most superior gas¯eld can be achieved with the one including 8 larger central inlets and 24 smaller outskirt inlets. Finally, an actual deposition experiment is carried out and its result indicates that adopting the optimized such inlet arrangement could generate a highly uniform and homogeneous growth environment on whole deposition area.

The Effect of the Gas Outlet on the Gas Velocity Field in Mass-Production of HFCVD Diamond-Coated Drills

“…The structure of this multiinlets arrangement is obtained according to the optimization results of our other study on the e®ect of gas inlet on the gas¯eld. 22 As illustrated in Fig. 1(b), it consists of 32 inlets which are arranged as an 8 Â 4 matrix.…”

“…The e®ect of factors relative to gas inlet has been discussed in another study. 22 Based on the obtained optimal HFCVD setup, the e®ect of gas outlet is investigated using the¯nite volume method (FVM) simulation in the present study. With the FVM method, the°ux velocity¯eld of reactive gas, as well as the temperature¯eld, are calculated simultaneously for a tailored HFCVD setup designed for mass-production of diamond-coated drills such that the temperature e®ect can be included in the generated gas¯eld.…”