Creep-feed Deep Grinding Of Particulate Reinforced Titanium Matrix Composites

Particulate reinforced titanium matrix composites have high specific strength,high specific stiffness,high wear resistance and high temperature durability,which show great application potentials as important candidate structural materials in the aviation and aerospace industries.However,it is a typical difficult-to-cut material due to the co-existence of hard TiC reinforcements and high-strength Ti-6Al-4V matrix.The disadvantageous effects,i.e.,low processing efficiency,rapid tool wear,high processing costs,poor surface quality and grinding burn,have been an important barrier in improving the machining efficiency and raising the surface quality in conventional cutting and grinding particulate titanium matrix composites.Accordingly,experimental research on machinability on particulate titanium matrix composites in creep-feed deep grinding with corundum grinding wheels is performed.The grinding force and wheel wear,grinding temperature and heat distribution rate,surface integrity are analyzed to reveal the high efficiency grinding processing characteristics of particulate titanium matrix composites.The results obtained have an important theoretical and engineering value in achieving the high efficiency and precision machining of particulate titanium matrix composites.The main work and results are summarized as follows:(1)The grinding force and wheel wear in creep-feed deep grinding particulate titanium matrix composites are investigated.The grinding parameters and grinding wheel type have a significant influence on grinding force,the grinding force decreases with an increasing grinding speed and increases with an increasing workpiece speed and depth of cut.The grinding force with microcrystalline corundum wheel is smaller than that with other common corundum wheels,which shows that microcrystalline corundum wheel is the sharpest.Adhesion wear is dominated in creep-feed deep grinding particulate titanium matrix composites with microcrystalline corundum wheel,and the area of the adhesion wear increases gradually with the increase of depth of cut.(2)The grinding temperature and heat distribution ratio during creep-feed deep grinding particulate titanium matrix composites are investigated.The grinding temperature increases with the increase of grinding speed,workpiece speed and depth of cut.The grinding temperature with microcrystalline corundum wheel is smaller than that with other common corundum wheels.The grinding cooling liquids have two stages during creep-feed deep grinding process: nuclear boiling stage and film boiling stage.When the depth of cut is less than 0.6mm,the grinding coolingliquids appears nuclear boiling stage,the grinding temperatures are always below 130? due to the excellent cooling effects.But when the depth of cut is large than 0.8mm,the grinding heat entering into grinding workpiece in film boiling stage is much larger than that in nuclear boiling stage,therefore,grinding temperature are above 700 ? and grinding surface easily produce grinding burn.Heat distribution rates during nuclear boiling stage and film boiling stage are20~30% and 70~85%,respectively.(3)The grinding surface integrity of particulate titanium matrix composites during creep-feed deep grinding are discussed.The ground surface is consists of smearing,grinding groove due to plastic cutting mode of the titanium matrix alloy,while the removal of reinforcements is mainly by means of voids produced due to the fracture and pull-out of the reinforcing particles.The effect of grinding parameters on surface microhardness,microstructure and residual stress are analyzed.In view of the above,the optimal grinding parameters are proposed.