Influence of small amount of sintering additives on unlubricated sliding wear properties of SiC ceramics

Fully densified SiC ceramics were developed from commercially available beta-SiC powders using small amount (3 wt%) of AlN-Sc2O3 or AlN-Y2O3 additives by hot pressing at 2050 degrees C for 6 h in nitrogen atmosphere, and their wear properties were investigated by subjecting to self-mated sliding at different loads (1, 6 and 13 N) under unlubricated conditions. SiC ceramics prepared with 3 wt% AlN-Y2O3 additives consisted of mostly large equi-axed grains with amorphous grain boundary phase of similar to 1.2 nm thickness, whereas SiC ceramics sintered with 3 wt% AlN-Sc2O3 additives showed duplex microstructure of elongated and fine equi-axed grains with clean grain boundary. As the load was increased, the steady state coefficient of friction reduced from similar to 0.6 to similar to 0.2, and wear rate increased from 10(-6) to 10(-5) mm(3)/N.m. It was observed that the friction did not depend on the additive composition, while less wear was observed for the SiC ceramics sintered with 3 wt% AlN-Sc2O3 additives consisting of clean grain boundary. The material loss was increased with the increased amount of sintering additive to 10 wt%. The worn surface morphology revealed that the material was primarily removed via surface grooving and microcracking at 1 N load, while tribochemical wear dominated at 6 and 13 N loads. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.