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Tribological characterisation of siliconcarbonitride ceramics derived from preceramic polymers
(2006)
Amorphous SiCN ceramics were prepared in a laboratory scale as disk shaped specimens with 10 mm diameter and 0.3 mm thickness. The friction and wear behaviour was characterised in gross slip fretting tests under unlubricated conditions at room temperature against steel (100Cr6) and ceramic (Al2O3). Tests with a ball-on-disk contact were performed in laboratory air with different content of water vapour. The results show clearly that the relative humidity has a significant effect on friction and wear behaviour. All tests in dry air lead to higher friction and higher wear rate than in normal air. Improved friction and wear behaviour was observed with increasing pyrolysis temperature up to 1100 °C of the SiCN specimens. This is attributed to increasingly better mechanical properties and higher stiffness of the amorphous network due to the evaporation of gaseous organic species and the formation of free graphite like carbon.
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.