Cutting Performance Of Cubic Boron Nitride Coated Cutting Tools

Cubic boron nitride?cBN?is the second hardest and second most thermally conductive material next to diamond;and it has high thermal stability and excellent chemical inertness against ferrous materials at temperatures up to 1200°C,while diamond possesses extreme affinity with iron at 600°C.The unique combination of the outstanding physical and chemical properties of cBN makes it the most promising solution in machining difficult-to-cut ferrous materials.Here,we are focus on the cutting performance of cBN-coated cutting tools,involving the experiments on cutting force,cutting temperature and tool wear,as well as the finite element simulation in cutting force,cutting temperature and temperature distribution.The main conclusions are summarized as follows:?1?Cutting force and cutting temperature of cBN-coated cutting tools were experimentally investigated by dry turning hardened ductile iron.Effect of the depth of cut?a_p?and cutting speed?v_c?on cutting force?F?,cutting temperature?T?dependent on v_c,were analyzed compared to titanium aluminum nitride?TiAlN?-coated cutting tools.We found that cutting force components of F_x,F_y,F_z are increased with the increase of a_p;especially,the F_y is the most largest among the three cutting force components.With the increase of v_c,F_y is decreased significantly while the changes of F_x,F_z are not obvious.Furthermore,Cutting temperature is increased with the increase of v_c.The reduction of cBN-coated cutting tools are 16.0%,52.0%,23.8%in cutting force components of F_x,F_y,F_z,respectively and are 19.0%-21.0%in cutting temperature,compared with TiAlN-coated cutting tools under identical conditions.?2?Cutting force and cutting temperature of cBN-coated cutting tools were analyzed by finite element methods?FEM?.FE model of cBN-coated cutting tools was built based on ABAQUS analysis software,and it was validated by the simulated results compared with.experimental results involving the cutting force and cutting temperature.The evolution of cutting force and temperature field distribution of cBN-coated cutting tools were obtained;the obvious temperature gradient distribution was observed in coated cutting tools,the maximum temperature occurs at rake face,and then decreses with the increase of tool depth.Compared to TiAlN coatings on cutting tools,cBN coatings on cutting tools shows the lower temperature and higher heat dissipation due to its lower friction coefficient and higher thermal conductivity.?3?Tool wear of cBN-coated cutting tools were analyzed experimentally.The flank wear width,wear morphology and the chemical composition of flank wear were investigated.Additionally,the wear modes and mechanisms were discussed briefly.We found that the average flank wear rates of uncoated Si₃N₄,TiAlN-coated and cBN-coated cutting tools are 607?m/km,472?m/km and 103?m/km,respectively;Further,the wear modes are crater wear on rake face and flank wear land,the wear mechanisms are abrasion and diffusion for cBN-coated cutting tools.Compared to TiAlN-coated cutting tools,cBN-coated cutting tools perform lower cutting force and lower cutting temperature,less flank wear rate.Combination of the versatile properties of cBN-coated cutting tools involving lower friction coefficient,higher hardness,higher thermal conductivity make it exhibit more superior cutting performance in machining hardened materials.