Research On The Machined Surface Quality For Ti(C,N)-based Cermet Cutters Based On FEM

Machining of metal is an important processing technique applied widely in the manufacture. Various sophisticated equipments are developed continually,which call for good quality of components increasingly. Residual stress and work hardening have become the important factors affecting service properties and life of the components seriously.Therefore,research on the surface quality of components,which are machined by cutters made of new materials,have important significance for optimizing cutting parameters and promoting the quality of workpieces.Firstly, the Ti(C,N)-based cermet cutters were prepared according to the liquid-phase sintering method and the material properties were measured and calculated.Secondly, machining finite element models with different cutting speed and feed were created.Then the rule of cutting speed and feed affecting the residual stresses existing in the surface layers and interior of workpieces were obtained and analyzed by considering mechanical and thermal stresses synthetically.According to the actual cutting conditions,machining finite element models with different cutting speeds and feeds were created,from which the rules of cutting speeds and feeds affecting equivalent strain in the surface layers and depths of deformation layers were obtained.Thirdly,the experiments that blanks of 45 steel were machined by the prepared Ti(C,N)-based cermet cutters were carried out.Then metallic phase and microhardness of the specimens gotten from the workpieces were tested and the rules of cutting speeds and feeds affecting the two work-hardening assessment indexes, surface hardening and depth of hardened layer were obtained,which proved the conclusions obtained from the finite element analysis.Finally,the mechanisms of surface hardening were illustrated in the viewpoints of microscope and thermo-mechanical coupling.Through the above researches,some important conclusions are drawn as follows:Firstly,the stresses in the surface layers are all tension stresses.When feed is fixed, maxium surface tension stress,maxium interior compression stress and the level of compression stresses all increase with cutting speed increasing.Cutting speed influence the depth of tension stresses layer morderately.The level of residual compression stresses increases with feed increasing,while the rules of surface maxium tension stress varying with feed are not constant in the conditions of different cutting speeds. Secondly,the rules of cutting speed and feed influencing the depth of hardened layer and surface hardening are different.The depth of hardened layer and surface hardening all first increases and then decreases with cutting speed increasing.The depth of hardened layer first declines and then increases with feed increasing,while the extent of surface hardening first increases and then decreases.Additionally,some conclusions are drawn through further discussions about the experiment results as follows:Serious work-hardenings are tend to happen in the semi-finishings carried out in mediate speeds and the surfaces may be softened in the turnings with high speeds.The conclusions of the issue indicate that the FEA of metal cutting could not only provide a qualitive and quantitative method of analyzing residual stresses and work-hardenings in machined workpieces,but also predict the surface quality of workpieces machined by cutters made of new materials,which has instructional significance to practical productions.