Laser micro-nano texturing of a polycrystalline ultra-hard cutting tool to improve wear behaviour

Polycrystalline diamond cutting tools are widely used for drilling and turning applications due to their high wearresistance and long durability, however the issue of adhesion of workpiece to the cutting tool significantly affects thecutting tool lifetime. Using a nanosecond fibre laser surface texturing of polycrystalline diamond single point cuttingtools is proposed to improve diamond wear and anti-adhesion properties in machining aluminium alloys. The textures,with topographical features’ depths and pitch ranging from tens of nanometers to tens of micrometers, were first milled using a 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 and Energy Dispersive X-Ray (EDX). The effect of different textures on the wear properties was investigated in turning tests under dry conditions. The tests were stopped every 20 passes and the wear analysed through an Alicona optical 3D measurements. The online monitoring and post-processing of the cutting forces and the microscopical characterisation of the tested cutting tools allowed the evaluation of the effects of texture design and adhesive properties. For textures depths in the order of 260 nm and post process roughness in the order of tens of nanometers, a reduction of cutting force and an improvement of antiadhesive effect were achieved in dry turning.</p

Surface engineering of ultra-hard polycrystalline structures using a nanosecond Yb fibre laser: Effect of process parameters on microstructure, hardness and surface finish

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 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, micro-indentation tests revealed an improvement of hardness from 75?GPa to 240?GPa at a depth of 350?nm, and to 258?GPa at a depth of 650?nm 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.</p

Surface engineering of ultra-hard polycrystalline structures using a nanosecond Yb fibre laser: Effect of process parameters on microstructure, hardness and surface finish

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 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, micro-indentation tests revealed an improvement of hardness from 75?GPa to 240?GPa at a depth of 350?nm, and to 258?GPa at a depth of 650?nm 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.</p

Laser micro-nano texturing of a polycrystalline ultra-hard cutting tool to improve wear behaviour

Polycrystalline diamond cutting tools are widely used for drilling and turning applications due to their high wearresistance and long durability, however the issue of adhesion of workpiece to the cutting tool significantly affects thecutting tool lifetime. Using a nanosecond fibre laser surface texturing of polycrystalline diamond single point cuttingtools is proposed to improve diamond wear and anti-adhesion properties in machining aluminium alloys. The textures,with topographical features’ depths and pitch ranging from tens of nanometers to tens of micrometers, were first milled using a 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 and Energy Dispersive X-Ray (EDX). The effect of different textures on the wear properties was investigated in turning tests under dry conditions. The tests were stopped every 20 passes and the wear analysed through an Alicona optical 3D measurements. The online monitoring and post-processing of the cutting forces and the microscopical characterisation of the tested cutting tools allowed the evaluation of the effects of texture design and adhesive properties. For textures depths in the order of 260 nm and post process roughness in the order of tens of nanometers, a reduction of cutting force and an improvement of antiadhesive effect were achieved in dry turning.</p

Microhardness and wear behaviour of polycrystalline diamond after warm laser shock processing with and without coating

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.</p

Challenges and strategies of decarbonising the steel sector

The steel sector is a foundation of modern society and is present in many aspects of our lives. The industry has over the last decade been facing increased environmental and climate pressure to lower its carbon footprint while remaining economically competitive. Decarbonizing this sector is challenging but, nevertheless, key for achieving climate goals. OECD data has shown that the sector accounts for around 6-8% of man-made global emissions from the energy sector. There have been efforts to decarbonize iron and steel production globally, and this article examines those challenges along with the strategies available to industry to achieve low-carbon and, ultimately, green steel in the coming decades.</p

Microhardness and wear behaviour of polycrystalline diamond after warm laser shock processing with and without coating

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.</p

Challenges and strategies of decarbonising the steel sector

The steel sector is a foundation of modern society and is present in many aspects of our lives. The industry has over the last decade been facing increased environmental and climate pressure to lower its carbon footprint while remaining economically competitive. Decarbonizing this sector is challenging but, nevertheless, key for achieving climate goals. OECD data has shown that the sector accounts for around 6-8% of man-made global emissions from the energy sector. There have been efforts to decarbonize iron and steel production globally, and this article examines those challenges along with the strategies available to industry to achieve low-carbon and, ultimately, green steel in the coming decades.</p

Kriging?based robotic exploration for soil moisture mapping using a cosmic?ray sensor

Soil moisture monitoring is a fundamental process to enhance agricultural outcomes and to protect the environment. The traditional methods for measuring moisture content in the soil are laborious and expensive, and therefore there is a growing interest in developing sensors and technologies which can reduce the effort and costs. In this work, we propose to use an autonomous mobile robot equipped with a state?of?the?art noncontact soil moisture sensor building moisture maps on the fly and automatically selecting the most optimal sampling locations. We introduce an autonomous exploration strategy driven by the quality of the soil moisture model indicating areas of the field where the information is less precise. The sensor model follows the Poisson distribution and we demonstrate how to integrate such measurements into the kriging framework. We also investigate a range of different exploration strategies and assess their usefulness through a set of evaluation experiments based on real soil moisture data collected from two different fields. We demonstrate the benefits of using the adaptive measurement interval and adaptive sampling strategies for building better quality soil moisture models. The presented method is general and can be applied to other scenarios where the measured phenomena directly affect the acquisition time and need to be spatially mapped.</p

Kriging?based robotic exploration for soil moisture mapping using a cosmic?ray sensor

Soil moisture monitoring is a fundamental process to enhance agricultural outcomes and to protect the environment. The traditional methods for measuring moisture content in the soil are laborious and expensive, and therefore there is a growing interest in developing sensors and technologies which can reduce the effort and costs. In this work, we propose to use an autonomous mobile robot equipped with a state?of?the?art noncontact soil moisture sensor building moisture maps on the fly and automatically selecting the most optimal sampling locations. We introduce an autonomous exploration strategy driven by the quality of the soil moisture model indicating areas of the field where the information is less precise. The sensor model follows the Poisson distribution and we demonstrate how to integrate such measurements into the kriging framework. We also investigate a range of different exploration strategies and assess their usefulness through a set of evaluation experiments based on real soil moisture data collected from two different fields. We demonstrate the benefits of using the adaptive measurement interval and adaptive sampling strategies for building better quality soil moisture models. The presented method is general and can be applied to other scenarios where the measured phenomena directly affect the acquisition time and need to be spatially mapped.</p