TEM investigations of wear mechanism of Al2O3 and Si3N4 compacts with GLPs additions

Extended lifetime of ceramic cutting plates is ever more desired. One way of approaching it entails sintering precursor materials with graphene-like nanoplatelets (GLPs) acting as solid lubricants. Therefore, Al2O3 and Si3N4 ceramic powders with addition of GLPs of grade 3 (fine) or grade 4 (coarse) were Spark Plasma Sintered. It is found that the 0.15 wt% GLPs addition of both grades allows to keep hardness practically at the same level as GLPs-free compacts (~16 GPa). Only larger GLPs additions (2 wt%) caused its evident decrease (down to 14−15 GPa). The ball-on-disc test revealed that only Al2O3+0.15 wt% GLPs(3) shows a 50% reduction in wear rate. The post mechanical test examination by SEM confirmed that Al2O3 compacts with small GLPs showed smooth wear track, as opposed to those having a Si3N4 matrix with large meandering cavities. TEM observations revealed that the wear damage caused by the ball was restricted to ~2 µm deep sub-surface areas, while, carbon is found to transfer from the GLPs agglomerates into tribo-film. The present experiments showed, that ceramic sinters with small addition of GLPs platelets could exhibit lower wear than GLPs-free ones and therefore show a potential for application as cutting plates.