Abstract
Polycrystalline diamond (PCD) tools are widely used in industry due to their outstanding physical properties. However, the ultra-high hardness of PCD significantly limits the machining efficiency of conventional abrasive grinding processes, which are utilized to manufacture PCD tools. In contrast, electrical discharge grinding (EDG) has significantly higher machining efficiency because of its unique material removal mechanism. In this study, the quality and performance of PCD tools machined by abrasive grinding and EDG were investigated. The performance of cutting tools consisted of different PCD materials was tested by high-speed turning of titanium alloy Ti6Al4V. Flank wear and crater wear were investigated by analyzing the worn profile, micro morphology, chemical decomposition, and cutting forces. The results showed that an adhesive-abrasive process dominated the processes of flank wear and crater wear. Tool material loss in the wear process was caused by the development of thermal cracks. The development of PCD tools’ wear made of small-sized diamond grains was a steady adhesion-abrasion process without any catastrophic damage. In contrast, a large-scale fracture happened in the wear process of PCD tools made of large-sized diamond grains. Adhesive wear was more severe on the PCD tools machined by EDG.
Highlights
Due to the ultra-high hardness and excellent thermal conductivity, polycrystalline diamond (PCD) tools have been extensively applied in the manufacturing of turbine blades, blade disks, fuselage, and medical implants, which are made of hard-to-machine materials such as titanium alloys, carbon fiber reinforced plastics, tungsten carbide, and various metal matrix composites [1,2,3,4,5,6]
The surface roughness of the tools machined by electrical discharge machining (EDM) was about 100 nm larger than that machined by abrasive grinding
Cobalt can be found on the surface of tool 002A (Figure 3a), while large-sized diamond grains were found on the surface of tool 302A, and pool-like cobalt was found between the diamond grain boundaries (Figure 3c)
Summary
Due to the ultra-high hardness (up to 10,000 HV) and excellent thermal conductivity (around 1000 W/mK), polycrystalline diamond (PCD) tools have been extensively applied in the manufacturing of turbine blades, blade disks, fuselage, and medical implants, which are made of hard-to-machine materials such as titanium alloys, carbon fiber reinforced plastics, tungsten carbide, and various metal matrix composites [1,2,3,4,5,6]. The hardness of PCD is ultra-high, abrasion, adhesion, chipping, and chemical diffusion could be found on the worn PCD tools in the machining of Ti alloys due to the severe cutting conditions. Li et al [27] further investigated the wear mechanism of the PCD tools machined by different grinding methods in turning of Ti6Al4V. By testing the performance of the cutting tools via turning Ti6Al4V at 160 m/min, it was found that flank wear width (VB) of the ground PCD tool was the largest, followed by those of the tools machined by “two-step” and “three-step” EDG. The performance of different PCD tools in high-speed machining of titanium alloy was comprehensively investigated. The worn profile, micro morphology, chemical decomposition, and cutting forces were analyzed to compare the performance of the different PCD tools in the cutting processes
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