Study of deposition diamond to fill pores on cobalt removal surface adopting HFCVD method

Abstract

While the presence of cobalt in conventional PCD tools had a detrimental effect on their cutting performance throughout the cutting process, cobalt removal PCD likewise had the issue of poor performance improvement. To address the issue of PCD's poor cutting performance, the pores remaining on the PCD surface after cobalt removal were filled using hot filament chemical vapor deposition (HFCVD). This relatively simple and effective approach was estimated to increase the cutting performance of PCD tools. For deposition, the carbon concentration was limited to 1%, 2%, 3%, 4%, and 5%, denoted by the numbers 1#, 2#, 3#, 4#, and 5#, respectively. SEM was used to observe the surficial and cross-sectional morphologies of the deposited PCD. The porosity of the deposited PCD surface was quantified using ImageJ software. X-ray diffraction and Raman spectroscopy were used to evaluate the diamond particle size and purity. The abrasion rate of the samples was determined using an abrasive rate tester. The flank wear of tools was then determined using a digital microscope, and the abrasion morphologies of tools were studied using an optical microscope following cutting. The results suggest that when the carbon concentration increases, the pores filling effect becomes superior and eventually inferior. The surface porosity of 2# is only 6.52%, which reaches the minimum, and that means 2# possesses the best pore filling effect. At the same time, 2# diamond grain size is the smallest, with relatively good purity and the smallest internal stress. When morphology and flank wear measures of cutting tools are compared, the tool life of 2# is almost double that of a general PCD tool. Thus, maintaining a carbon concentration of about 2% efficiently fills the pores of cobalt removal PCD, significantly improving the wear resistance and durability of the tools. In general, this study used HFCVD to deposit diamond to fill pores on the cobalt removal surface of the PCD tools. It was found that maintaining not too high carbon concentration can enhance the quality of diamond and filling ration, therefore improving the wearing performance of PCD tools. This experiment attempted to demonstrate the concept of utilizing diamond as a dense cover layer to deposit diamond grains into PCD tool pores. Then, carbon concentration was included as a significant factor in the deposition process in order to investigate the propensity of diamond pore nucleation and growth in order to fill the pores on the surface with the greatest possible quality. Finally, when the results of pore filling were compared to the results of real cutting, it was found that the cutting performance of PCD tools with improved filling was superior to that of conventional PCD tools.