Thermo-chemical Erosion Of Natural Diamond Tools Under Vacuum Atmosphere

Natural diamond tools due to its high hardness and wear resistance, low frictioncoefficient, the minimum radius of the blade and the smooth edges, etc, are theindispensable tool of ultra-precision machining, their manufacturing technology is alsothe most basic supporting technology and the basic of the ultra-precision machiningindustrial chain. Mechanical lapping is the most common and mature technology incurrently manufacturing industry of natural diamond tools. Mechanical lappinginevitably causes damage to the tool surface, reducing the tool surface quality andmechanical properties, affecting the tool life, increasing the cost of manufacturing tool,to a certain extent, restricting the development of processing technologies. Therefore,how to remove the damaged layer without causing secondary damage to the tool is theurgent problem to be solved in the current mechanical lapping diamond tools.Firstly, the microscopic mechanism of damage layer in mechanical lapping isdiscussed using the natural diamond tools’ mechanical lapping techniques and moleculardynamics simulation, simulated the mechanical lapping process which used the (100)and (110) crystal plane as the rake faces, the <100> crystal orientation as the lappingdirection. We got the microscopic mechanism of material removal on the rake faces andlapping direction: sp3-sp2order-disorder transition. And based on the removalmechanism, we got the composition of damaged layer: sp3hybridized structure ofdiamond carbon atoms, orderly sp2hybridized structure of graphite, disorderly sp2andsp hybridized structure of amorphous carbon. Calculated the hardness and elasticmodulus by the nanoindention, the hardness and elastic modulus of the diamond layerare both less than the diamond without damage.According to the microscopic mechanism of damage layer, this paper presented anon-mechanical stress damage layer removal post-treatment: Thermo-chemical erosionof damage layer under vacuum atmosphere. Analyzed the erosion parameters affectingthe surface roughness and mechanical properties of the tools, and established the craftwhich can significantly reduced the tool flank face roughness and improved the toolsurface hardness and elastic modulus.In addition, for the hardness of diamond tool’s surface still improved which treatedwithout chemical catalyst under vacuum annealed (473K) phenomenon, we usedmolecular dynamics method to simulate the heat treatment of diamond tools aftermechanical lapping. We got that disorderly sp2and sp hybridized structure in damage layer transformed into sp3hybridized structure, that carbon atoms in damage layerthrough self-healing under vacuum annealed, rebuilding the structure of diamond andrestoring the hardness. Whereby, we got the microscopic mechanism of removingdamage layer: thermo-chemical erosion and the carbon atoms’ rebuilding under vacuumannealed.Finally, we carried the test that how the craft of thermo-chemical erosion affectingthe tool’s durability, established the program that cutting Ge with diamond tool and theevaluation criteria of diamond tool’s durability, selected the cutting parameters of plasticremoving mode. And we got the comparative analysis of untreated and treated tool’sdurability: the durability of the treated tool increased1.2times compared to theuntreated tool.