Grinding Characteristics of MoS_(2)-Coated Brazed CBN Grinding Wheels in Dry Grinding of Titanium Alloy

As an important green manufacturing process,dry grinding has problems such as high grinding temperature and insufficient cooling capacity.Aiming at the problems of sticking and burns in dry grinding of titanium alloys,grinding performance evaluation of molybdenum disulfide(MoS_(2))solid lubricant coated brazed cubic boron carbide(CBN)grinding wheel(MoS_(2)-coated CBN wheel)in dry grinding titanium alloys was carried out.The lubrication mechanism of MoS_(2)in the grinding process is analyzed,and the MoS_(2)-coated CBN wheel is prepared.The results show that the MoS_(2)solid lubricant can form a lubricating film on the ground surface and reduce the friction coefficient and grinding force.Within the experimental parameters,normal grinding force decreased by 42.5%,and tangential grinding force decreased by 28.1%.MoS_(2)lubricant can effectively improve the heat dissipation effect of titanium alloy grinding arc area.Compared with common CBN grinding wheel,MoS_(2)-coated CBN wheel has lower grinding temperature.When the grinding depth reaches 20μm,the grinding temperature decreased by 30.5%.The wear of CBN grains of grinding wheel were analyzed by mathematical statistical method.MoS_(2)lubricating coating can essentially decrease the wear of grains,reduce the adhesion of titanium alloy chip,prolong the service life of grinding wheel,and help to enhance the surface quality of workpiece.This research provides high-quality and efficient technical support for titanium alloy grinding.

Effect of Gd addition on mechanical and microstructural properties of Mg-xGd-2.6Nd-0.5Zn-0.5Zr cast alloys

The Mg-xGd-2.6Nd-0.5Zn-0.5Zr(x=0,3.0,4.5 and 6.0,wt.%)alloys were prepared by gravity casting and then T6 treatment.Microstructures of the alloy were observed using optical microscopy and scanning electron microscopy.Results show that the as-cast alloys contained network Mg3Gd phases,blocky and needle-like Mg12(Nd,Gd)phases.The a(Zr)particle inclusions in the a(Mg)matrix are also observed.Content of the secondary phases decreases as Gd content increases.Tensile test results show that the tensile and yield strengths of all the alloys increase as Gd content increases under the as-cast and T6 conditions,but the elongation exhibits the opposite trend.The blocky Mg12(Nd,Gd)phases appear and act as crack initiator and deteriorates the experimental alloys’ductility with the increase of Gd content,especially as Gd content increases to 6.0 wt.%,so the Mg-6.0Gd-2.6Nd-0.5Zn-0.5Zr alloy has the lowest elongation value compared to the other alloys studied.After T6 treatment,the Mg-4.5Gd-2.6Nd-0.5Zn-0.5Zr alloy exhibits the optimal mechanical properties both at room temperature and 250℃.