Study Of Microstructures And High Temperature Tribological Performances Of Mesophase Carbon Alloys

Based on high temperature lubrication theory, this thesis introduced a specific category of layered carbonaceous substances named Meso-Carbon Micro-Beads (abbreviated as MCMB) into tribology. Adding one or several powders of Ti, Ni,B, and MoS₂ into the carbonaceous mesophases by mechanical alloying, the metastable mesophase carbon alloys were prepared, And Their structures and high temperature tribological performances were investigated.In the process of mechanical alloying, the effects of the types of added elements and the ball milling time on the microstructure and morphology of the mesophase carbon alloys were characterized by using XRD and SEM. The high temperature tribological performances of the mesophase carbon alloys as lubricating additives under different experimental conditions were investigated using a MMU-5G high temperature friction and wear tester. Worn morphologies, types of elements and structural changes on the worn surfaces were examined by using SEM, EDS and Raman, respectively.The results have shown that, the mechanical alloying treatment results in a bigger non-order degree of the mesophase carbon alloys and a transition to amorphous state. But the Ti/Ni doped CM through mechanical alloying for 50 hours shows an increase in the crystallinity, implying a transition to the more ordered structures caused by the catalytic graphitization due to the doped Ti/Ni at lower temperatures. The mesophase carbon alloys , when used as lubricating additives, display a obvious high temperature anti-friction and wear resistant effect. The high temperature anti-friction and wear resistant effects are influenced by milling time, load, temperature and speeds of rotation. As for the mesophase carbon alloy Ti/Cu doped through mechanical alloying for 10 hours and the mesophase carbon alloy Ti/Ni for 50 hours , when used as lubricating additives, the lager the applied load, the lower the friction coefficient and thewear severity, as well as the larger of microcrystalline planar size (La) of the wear surface.The mesophase carbon alloys doped with B through mechanical alloying for 120 hours and doped with MoS₂/B for 80 hours, when used as lubricating additives, the friction coefficients show an obvious drop with increasing temperature. When the mesophase carbon MoS₂/B doped through mechanical alloying for 80 hours is used as lubricating additives, the friction coefficient drops to approximately zero at 450℃. In addition, the element B doped into the mesophase carbon alloys transfers onto the worn lower specimen surfaces, thus leading a lower wear severity.