Ceramics are of increasing interest for application in many branches of technique. In order to improve the tribological performance of ceramic materials, composites on the basis of silicon carbide with different amounts of titanium carbide, boron carbide, titanium diboride and free carbon in the form of graphite were manufactured by a reaction sintering process.
The friction and wear behaviour of these composites was investigated with oscillating sliding motion in unlubricated tests at room temperature on different levels of relative humidity. Additional tests were performed under water lubrication, revealing the superior behaviour of composites for special test conditions. A major influence of the free carbon on friction or wear behaviour was not observed. The tribological behaviour in air as well as under water is mainly dependant on the amount of titanium phases.
Ceramic particulate composites in the system SiC-TiC-TiB2 sliding against SiC and Al2O3 under water
(1999)
The tribological behaviour of SiC, SiC-TiC and SiC-TiC-TiB2 was determined in oscillating sliding against SiC and -Al2O3 in water at room temperature. The tribo-systems with the composite materials containing TiC and TiB2 differ significantly from the systems with the single phase SiC: The wear is reduced and the friction is increased. The wear reduction up to a factor of 10 is mainly due to the formation of an oxide film containing titanium oxides which is soft, stable in water and well adhering to the bulk material. This oxide film is transferred to the alumina ball but not to the silicon carbide ball.
The friction and wear behaviour of SiC, Si3N4 and SiC/Si3N4 composite ceramics were investigated with oscillating sliding (gross slip fretting) at room temperature. The influence of counter body material and the humidity of the surrounding air was studied with a ball-on-disc configuration with different ball materials (1000Cr6, Al2O3 SiC and Si3N4). The effect of RH on friction is marginal with exception of SiC (low friction) as counter body material. The wear behaviour, however, is strongly affected by humidity, showing inverse trends for different counter body materials. Consequently, the wear behaviour of a tribo couple can be improved by selecting an adequate mating material. The results reveal the necessity to control RH in tribological tests. For estimation of the performance of tribo couples under varying environmental conditions, a variation of RH is required. In tribo couples with single phase SiC, either as ball or disc, the tribological behaviour of the system is dominated by SiC. The friction behaviour of the composite material is in between the behaviour of the two single phase materials, Si3N4 and SiC, whereas the wear behaviour is very similar to that of single phase Si3N4.