Abstract: Superhard diamond is a tool material for machining hard parts, but precision machining needs to control its cutting edge morphology.Based on the diamond removal mechanism by thermochemical graphitization, a diamond grain truncating technology coupling discharge thermal and alternating cutting force is proposed to ensure the consistency of discrete grain cutting edges in a grinding.In the truncating, the discharge thermal between the grinding wheel and electrode is transmitted to the grain cutting interface through the chip, and then fused with the friction thermal.The alternating cutting force is used to enhance the thermochemical graphitization removal on the cutting interface.Furthermore, the thermomechanical couple mechanism is explored for the graphitization temperature and temperature rate of cutting edge.The effect of alternating cutting force on grain truncation area, truncating efficiency and grinding quality is analyzed.It is showed that iron atom is easier to diffuse with diamond atoms than copper atoms, the graphitization temperature of diamond can be reduced from 850℃ by copper atom to 750℃ by iron atom.Under the catalysis of iron atom, the coupling of alternating force and discharge thermal can improve the temperature rate of cutting edge, increase the diamond truncating efficiency by ca.20 times and the grain truncation area by ca.3 times.Finally, dry grinding of hard die steel with#46 rough diamond grains truncated can reduce stress concentration and avoid thermal damage.The roughness can be reduced to 290 nm, so as to realize environmental protection and efficient precision machining.

Key words: diamond grain, thermochemical remove, discharge machining, precision grinding