Study On Carbide Cutting Tool's Surface Micro-texture Processed By Nanosecond Laser And Its Correlative Mechanisms

Micro-texture tool is a new tool which can improve the cutting performance and may solve the machining problem of hard materials.In recent years,it has been found that the addition of specific patterns on cutting tool will change the surface structure,resulting in the reduction of the chip contact length,the increase of the shear angle and the reduction of the cutting force.In addition,micro-texture can collect wear debris,and make cutting fluid better enter the cutting zone,thereby reducing surface wear and increasing tool life.In this paper,two kinds of micro-textures,groove type and honeycomb type,were designed and fabricated on the surface of YG8 cemented carbide by laser machining.Based on the laser processing parameters and the micro-texture design parameters,the micro-texture is optimized.The influence of the micro-texture parameters on the surface wettability,the friction and wear properties was studied by combining theory and experiment,and the relationship between the two properties was discussed.Thus,a kind of micro-texture design and optimization idea with high wear reduction ability is obtained.Firstly,the ablation threshold theory suitable for the elliptical spot of semiconductor laser is firstly derived.Combined with the experiment,the size of the spot is obtained.The ablation threshold value of YG8 material under the action of multiple pulses and its variation rule can be used to guide the selection of laser processing parameters.Secondly,the influence of laser processing parameters on the surface micro-texture of YG8 cemented carbide was studied.The influences of laser machining parameters on the integrity and structural parameters of micro-grooves were discussed by orthogonal experiment and single factor experiment respectively.It is found that the laser power and pulse repetition frequency are the two most important factors affecting the micro-texture integrity.Different laser parameters have different effects on the micro-texture size.It provides reference for the preparation of samples in the study of micro-texture properties.Thirdly,the classical Wenzel and Cassie-Baxter contact models were used to derive the theoretical contact Angle formula for the groove and honeycomb micro-textures,and the theoretical influence rules of the micro-texture parameters were obtained.It is found that honeycomb surface is more hydrophilic than groove surface at the same texture density under Wenzel contact condition.The wettability experiments of different micro-texture surfaces found that the contact Angle increased with the increase of micro-texture density,and the depth of micro-grooves would affect the liquid penetration effect.Finally,the friction and wear experiments of the two micro-textured surfaces under dry/wet conditions were carried out.The friction coefficient and wear morphology of the two micro-textured surfaces under different textures and friction directions were compared.The wear mechanism of the surface micro-textured surfaces and the friction reduction mechanism under dry/wet conditions were analyzed.The results show that the micro-texture reduces wear by collecting wear debris under dry friction,and the stronger wear reduction ability is due to the stronger collection efficiency of the micro-texture when the friction direction is perpendicular to the microgroove direction.Micro-texture storage of cutting fluid under wet friction can achieve better lubrication effect.The wettability and tribological and wear properties caused by the change of micro-texture were compared.It was found that when the texture density was larger,the more hydrophilic the micro-texture surface was.the better the permeability was,the smaller the friction coefficient and the lower the wear was.In general,the surface with better wettability has a stronger wear reduction effect.In this paper,the micro-texture,wettability and friction and wear properties of laser-machined cemented carbide surface are studied,which provides a new reference for the preparation of micro-texture surface and the optimal design idea,and has an important guiding significance for the design of micro-texture tool.