Influence of fabrication of SiC on tribological behavior of C/C-SiC composite against 40Cr steel

Four C/C-SiC composites were prepared using molten-Si infiltration-reaction(MSI) or precursor-pyrolysis(PIP),respectively.The sliding tribological behaviors of these four composites and one C/C composite were tested by M2000 wear tester.The results show that the coefficients of friction(COF) of the two kinds of MSI-composites are high under the applied loads and time,which fluctuate in 0.404?0.906.With increasing loads the COF of composite B with 40.9%(mass fraction) MSI-SiC has lower fluctuation than those of composite A with 18.9% MSI-SiC.But with prolonging time,the COF of composites A has larger changing extent than those of composite B except that under 150N.For the two PIP-composites,the COF are low and stable,which fluctuate in 0.08?0.144.But with increasing load,composite C with 18.0% PIP-SiC has a little larger changing extent than composite D with 6.0% PIP-SiC.The EDAX results show that the carbon element has not been found on part of the worn surface of composite B.The molar ratio of carbon to silicon on the worn surface of composite C is higher than 1,which indicates that carbon friction film can easily form with good lubrication to decrease the COF.SEM images of the MSI-composites have very rough friction films while the PIP-composites have smooth and integrated ones.