The use of lasers for near-net shape manufacturing of cutting tools, made of ultra-hard materials such as polycrystalline diamonds, is recently becoming a standard processing step for cutting tool manufacturers. Due to the different machinability exhibited by microstructurally different composites, the laser processing parameters and their effects need to be investigated systematically when changing the material. In this context, the present paper investigates the effects of a fibre laser milling process (nanosecond pulse duration) on surface topography, roughness, microstructure and microhardness of two 2 microstructurally different polycrystalline diamond composites. Pockets were first milled using a pulsed ytterbium-doped fibre laser (1064 nm wavelength) at different fluences, feed speeds and pulse durations, and finally characterised using a combination of Scanning Electron Microscopy, White Light Interferometry, Energy Dispersive using X-Ray (EDX) and micro hardness analyses. For laser feed speed in the region of 1000 mm/s, microindentation tests revealed an improvement of hardness from 75 GPa to 240 GPa at a depth of 350nm, and to 258 GPa at a depth of 650nm below which the microstructure is preserved as confirmed by microscopy images of the analysed cross sections. For fluences in the region of 11.34 Jcm-2 a variation of cobalt binder volume between the two composites causes a change in milling mechanism. At fluences below 20 Jcm-2 , the proposed milling process for CTM302 resulted in a microstructural change (ultra-hard grain size and Cobalt binder weight), better surface integrity (140 nm) and improvement of micro hardness (up to 258 GPa). The properties achieved through the proposed process achieve better hardness and roughness when compared to laser shock processing. To the best of authors' knowledge, it is reported for the first time that an increase of hardness accompanied by improved surface roughness can be achieved on polycrystalline diamond through low-energy laser processing.
Spotted wing drosophila, Drosophila suzukii, is a serious invasive pest impacting the production of multiple fruit crops, including soft and stone fruits such as strawberries, raspberries and cherries. Effective control is challenging and reliant on integrated pest management which includes the use of an ever decreasing number of approved insecticides. New means to reduce the impact of this pest that can be integrated into control strategies are urgently required. In many production regions, including the UK, soft fruit are typically grown inside tunnels clad with polyethylene based materials. These can be modified to filter specific wavebands of light. We investigated whether targeted spectral modifications to cladding materials that disrupt insect vision could reduce the incidence of D. suzukii. We present a novel approach that starts from a neuroscientific investigation of insect sensory systems and ends with infield testing of new cladding materials inspired by the biological data. We show D. suzukii are predominantly sensitive to wavelengths below 405 nm (ultraviolet) and above 565 nm (orange & red) and that targeted blocking of lower wavebands (up to 430 nm) using light restricting materials reduces pest populations up to 73% in field trials.
Cutting tools made of ultra-hard materials such as polycrystalline diamonds offer superior wear resistance in precision machining of Aluminium alloys. However, the wear properties of these materials are dependent on their microstructural characteristics such as grain size and binder percentage. In this context, the present paper evaluates the effects of two low-energy fibre laser processes (nanosecond pulse duration) on microstructural changes of polycrystalline diamond composites and consequently investigates wear and friction characteristics and micro hardness properties. Pockets were first achieved using a single mode SPI pulsed fibre laser (1064 nm wavelength) inducing both laser shock processing (LSP) and laser peening without coating (LPwC) and characterised using a combination of scanning electron microscopy (SEM), white light interferometry, energy dispersive X-Ray (EDX) and micro hardness analyses. The as-received and processed materials were tested on a pin-on-disc for the evaluation of their wear performance. An analytical model based on the asperities of pin and disc after wear test is proposed to predict the trend of wear performance of different laser-processed materials. LSP with vinyl and quartz at a scanning speed of 500 mm s-1 achieved a micro-hardness of 110 GPa at a depth of 632 nm. LPwC at 0.8 GW cm-2 produced hybrid microstructures which share characteristics of laser shock processing and selective laser melted structures. For laser feed speed in the region of 1000 mm s-1 , micro-indentation tests revealed an improvement of hardness from 70 GPa to 95 GPa at a depth of 670 nm for LPwC. Tribotest revealed enhanced wear performance for all laser-processed pins and reduced coefficient of friction also validated by increased material removal rate when compared to the as-received material. To the best of authors' knowledge, it is reported for the first time that an improvement of wear performance can be achieved on polycrystalline diamond through LSP and LPwC.
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