Study On Removal Mechanism In The Grinding Of CBN-WC-10Co Composites

The SPSed CBN-WC-10Co is a new composite exhibiting high strength and high hardness and better fracture toughness than CBN.Therefore,the CBN-WC-10Co composites have a widely prospect in application.However,the excellent mechanical properties of CBN-WC-10Co composites also make them very difficult to be machined.Grinding has the advantages of high processing accuracy,good surface quality and wide processing range.It is often applied in precision machining of the difficult-to-machine materials.Thus,it is an effective way to process the CBN-WC-10Co composites accurately.In this paper,the diamond grinding wheel was used to grind of CBN-WC-10Co composites;the grinding characteristics and material removal mechanism of CBN-WC-10Co composites were studied;the influence of grinding parameters on grinding force,specific grinding energy and surface quality were investigated.The main research contents are as follows:(1)Do the research on grinding forces of CBN-WC-10Co composites.The grinding force was measured with piezoelectric crystal dynamometer which revealed the effects of grinding parameters on grinding force and specific grinding energy.The results shown that both tangential and normal grinding forces increased rapidly with the increase of depth of cut;compared to the depth of cut,the table speed had little effect on the grinding force.With the increase of table speed,both the tangential grinding force and the normal grinding force rose slowly.The grinding force and the normal grinding force decreased with the increase of the wheel speed.The increase of depth of cut or table speed led the decrease of specific grinding energy.(2)Do the research on grinding surface quality of CBN-WC-10Co composites.The surface roughness was measured by using a surface profilometer.The morphology surface was observed by scanning electron microscopy.X-ray stress analyzer was applied to measure the residual stress.The results shown that with increase of the depth of cut and table speed,the scratches and accretions on the grinding surface increased.The scratches became wider and the surface roughness increased as well.The Grinding induced high compressive residual stress on the ground surface.The compressive residual stress of the WC phase increased with increase in depth of cut.However,when the grinding depth was large,the compressive residual stress decreased for CBN phase due to the fracture of the CBN particles.(3)Analyze the removal mechanism of CBN-WC-10Co composites.With the increase of the maximum undeformed chip thickness,the surface roughness increased and the surface texture of the workpiece deteriorated,the brittleness removal ratio increased and the grinding energy decreased at the same time.The CBN-WC-10Co composites had two types of removal modes.For WC-Co,the material removal was dominated by inelastic deformation.For CBN particles,however,the prevalence of removal mechanism was via brittle fracture.