Effect of laser texturing on the performance of ultra-hard single-point cutting tools

Abstract

This paper investigates the cutting performance and anti-adhesive properties of textured single-point polycrystalline diamond (PCD) cutting tools in machining Aluminium 6082 alloys. The micro/nano textures were first milled using a fibre laser (1064-nm wavelength) at different power intensities, feed speeds and pulse durations, and finally characterised using scanning electron microscopy, white light interferometry and energy dispersive X-ray spectroscopy. The effect of different textures on the cutting performance was investigated in turning tests under dry cutting conditions. The test was stopped at regular lengths of cut to allow analysis of height of adhesion through 3D white light interferometry. The data processing of the cutting forces and the microscopical characterisation of the tested cutting tools enabled the evaluation of the effects of texture design, friction coefficient and adhesive properties. The results indicated that feed force in tools with grooves perpendicular to the chip flow direction (CFD) was more stable (20-40 N) than the benchmark (6-41 N). Similarly, the thrust force for tools with grooves parallel to CFD and grooves perpendicular to CFD showed a homogeneous trend fluctuating between 60 and 75 N as compared with the benchmark (ranging between 73 and 90 N). For texture depth in the order of 260 nm and post process roughness in the order of tens of nanometers, a reduction of average friction coefficient (0.28 ± 0.14) was reported when using lasered inserts with grooves parallel to the chip flow direction compared with the benchmark tools (0.34 ± 0.26) corroborated by reduced stiction of workpiece material on the rake face. In machining via textured tools with grooves perpendicular to CFD, the cutting forces were reduced by 23%, and the surface quality of the machined workpiece was improved by 11.8%, making this geometry the preferred choice for finishing applications. Using grooves parallel to CFD reduced the cutting forces by 11.76%, adhesion by 59.36% and friction coefficient by 14.28%; however, it increased the surface roughness of the machined workpiece, making this geometry suitable for roughing operations. For the first time, laser manufacturing is proposed as a flexible technique to functionalise the geometrical and wear properties of PCD cutting tools to the specific applications (i.e. roughing, finishing) as opposed to the standard industrial approach to use microstructurally different PCDs (i.e. grain size and binder %) based on the type of operation.

Laser Processing of Hard and Ultra-Hard Materials for Micro-Machining and Surface Engineering Applications

“…Laser micro-textures can be classified into three main types: linear grooves ([ 76 , 92 , 100 ]), dimples ([ 101 , 102 ]), and rectangular pits ([ 58 , 103 , 104 ]). Other less used textures include elliptical ([ 105 , 106 , 107 ]), sinusoidal ([ 108 ]), chevron ([ 109 ]), and hybrid/texture combinations ([ 110 , 111 ]).…”

“… Texture dimension distribution based on the literature reviewed in this paper ([ 32 , 45 , 56 , 57 , 74 , 88 , 90 , 92 , 94 , 95 , 100 , 101 , 103 , 104 , 105 , 106 , 107 , 108 , 110 , 112 , 113 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , …”

“…The presence of micro-textures on a surface reduces the contact length between the workpiece and the cutting tool causing a general reduction in machining forces, COF, and cutting temperatures to various extents in dry cutting. Numerous studies have supported these improvements across a range of cutting tool materials: PCD (Ghosh and Pacella [ 100 ]), Su et al [ 119 ]), WC (Wang et al [ 161 ]), Titanium alloys (Niketh and Samuel [ 127 ], Costil et al [ 147 ]), PcBN (Pacella and Brigginshaw [ 94 ]), aluminium alloys (Liu et al [ 121 ], Mishra et al [ 109 ]) and Inconel 718 (Pang and Wang [ 124 ]). Textures also act as reservoirs for lubricant and debris.…”

“…Texture orientation and geometry strongly affect the frictional behaviour. Ghosh and Pacella [ 100 ] created linear grooves (width = 7 μm, depth = 260 nm and spacing = 20 μm) on the rake face of a PCD tool using a nanosecond fibre laser to investigate the effect of texture orientation in turning Al 6082. Three orientations were investigated: parallel to CFD, perpendicular to CFD and parallel to the main cutting edge (MCE) as shown in Figure 19 A.…”

“…As the chips harden, they form sharp regions and a secondary cutting edge on textures leading to a poorer surface quality on the workpiece [ 121 ]. Adhesion is heavily dependent on the workpiece material, but texturing can reduce its extent because of the reduced contact length [ 100 ]. Aluminium-based workpieces quickly reach temperatures that cause ductile behaviour causing chips to adhere to a tool [ 113 ], whereas Ti 6 Al 4 V workpieces are more likely to chip away with the pieces chemically reacting to the tool material [ 42 ].…”