Effects of Heat Treatment Temperature on Tribological Properties of Carbon/Carbon Composites with B_4C Additive

C/C composites with B_4C additive were prepared by chemical vapor infiltration and followed by resin impregnation/carbonization process with integrity felts with B_4C additive.The tribological properties of the composites treated at 2 000 ℃,2 300 ℃ and 2 500 ℃ respectively were investigated on an MM-1000 friction tester.For the composites treated at 2 000 ℃, the worn mechanism was grain-abrasion.The composites exhibited very severe abrasion and higher friction coefficient,and with obvious turnup tail in braking curve.For the composites treated at 2 300 ℃,boron carbide resulted in catalyze graphitization remarkably and the composites exhibited higher graphitization degree,smooth lubrication film was formed at worn surface,thus the composites exhibited very good abrasive resistance,lower friction coefficient and stable braking property.However,for the composites treated at 2 500 ℃,the graphitization degree was up to 97.8%,as a result,the abrasion and friction coefficient increased compared with those at 2 300 ℃,and braking curve exhibited violent fremitus.