Research On The Mechanism And Mechanical Properties Of Surface Residual Stress In High-speed Cutting Nickel-based Superalloy

In recent years,with the rapid development of China’s aerospace industry,higher requirements have been put forward for the material properties of parts.Nickel-based superalloy has good fatigue resistance,oxidation resistance,corrosion resistance and other characteristics,widely used in a variety of harsh environment,has become a popular parts processing materials,but in the process of its poor thermal conductivity,work hardening,processing efficiency is low,tool wear is serious,is a typical difficult to machining materials.High speed cutting technology has the characteristics of small cutting force and low cutting temperature in the process of machining,which can solve the problem of difficult machining materials.After machining,the surface quality of the workpiece has a great impact on the working performance and service time of the parts.As an important part,the machined surface residual stress plays an important role in the anti-fatigue strength and the stability of the geometric dimension of the workpiece,so it is necessary to study the residual stress and mechanical properties of the machined surface.In this paper,the nickel-based superalloy GH4169 was used as the research object.The chip forming force model was established based on the basic cutting theory and the material J-C constitutive equation,and the plough force model was established based on the Waldorf slip line theory considering the arc radius of the tool tip.The temperature of the workpiece in the cutting process was investigated by using the mirror heat source method,and the cutting temperature model was established considering the shear heat source on the shear surface of the first deformation zone and the friction heat source on the back cutter surface.The internal stress field of the workpiece was calculated according to Hertz contact theory,and the residual stress prediction model was established based on elastic-plastic mechanical loading,unloading and stress-strain release.The single-factor high-speed cutting experiments were designed to measure the cutting force and cutting temperature in the cutting process,and the experimental results were compared with the predicted results to verify the accuracy of the established model.The experimental results show that the cutting force decreases with the increase of cutting speed.With the increase of feed,the cutting force becomes larger and larger.With the increase of cutting speed and feed,the cutting temperature becomes higher and higher.The residual stress was measured by X-ray diffractometer,and the experimental results were compared with the predicted model results.The influence of cutting speed and feed rate on the residual stress was analyzed.The experimental results show that the surface of the workpiece is the residual tensile stress.With the increase of the distance from the surface of the workpiece,the residual tensile stress rapidly transforms into the residual compressive stress.The residual compressive stress gradually increases and reaches the maximum value,and finally decreases slowly and tends to zero.The surface of the workpiece after cutting was observed by the white light interferometer,and the roughness of the workpiece surface,the height of the wave peak and the distance between the two peaks were analyzed under different cutting parameters.In order to further explore the mechanical properties of the workpiece surface after cutting,a UMT friction machine was used to carry out friction experiments on the workpiece after cutting,the fixed load,speed and temperature were set,the friction coefficient in the friction experiment process was derived,and the depth and width of the workpiece surface wear mark and the wear of friction pair were analyzed after friction experiment.The experimental results show that the surface friction coefficient decreases first and then increases with the increase of cutting speed.With the increase of feed,the friction coefficient becomes larger and larger,which is mainly affected by the surface roughness of workpiece after cutting.