CERAMIC AND CERAMIC COMPOSITE-MATERIALS WITH IMPROVED FRICTION AND WEAR PROPERTIES

Dry friction and wear tests were performed with self-mated couples of SiC with 50 wt % TiC, Sic-TiB2, Si3N4 with 30 wt % TiN, Si3N4 with 5, 10 and 20 wt % BN and a binary carbo-nitride composite (Ti,Mo)(C,N) at room temperature and 400 degrees C or 800 degrees C. The results are compared with currently available SiC and Si3N4 materials. In a normal environment the examined ceramic composites used during these studies are able to form a lubricious oxide reaction layer or a film of an intrinsic solid lubricant on a hard substrate. The binary carbo-nitride composite had a wear coefficient smaller than 10(-6) mm(3). N-1.m(-1), sometimes smaller than 10(-7) mm(3). N-1.m(-1), that was independent of temperature from ambient up to m 800 degrees C. At 22 degrees C the addition of hexagonal BN reduced the friction of Si3N4. Simultaneously, the wear coefficient was independent of sliding velocity and below 10(-6) mm(3).N-1.m(-1). Friction and wear increased with increasing temperature. The addition of TiC to SiC reduced friction and wear. At room temperature, Si3N4-TiN exhibited a lower wear than Si3N4 At 800 degrees C, the wear coefficient of Si3N4 was reduced by two orders of magnitude by the addition of TiN as TiO2-x forming substrate. The addition of TiB2 to SiC was only beneficial at 400 degrees C and above 0.5 m.s(-1) compared to SiC by decreasing the wear coefficient.