Tribological Properties of SiC Whisker Containing Silicon Nitride Composite

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Abstract
The friction and wear characteristics of SiC whisker containing composite silicon nitride were studied. Silicon nitride powder which contains densification aids of Y2O3 and La2O3 was mixed with silicon carbide whiskers (10, 20, and 30 wt percent) and then hot-pressed at a temperature of 1800° C. Wear experiments were carried out with a ring on block type apparatus at the sliding conditions of the sliding speed of 314 mm/sec and the load of 5 N and experimental results showed that the SiC whisker had an evident effect to reduce the wear rate of silicon nitride blocks. Silicon carbide whiskers are not dispersed isotropically, but they are oriented to the direction which is perpendicular to the pressure of hot-press sintering. Therefore, wear characteristics of the composite ceramics are anisotropic. The effect of SiC whisker on wear rate of silicon nitride is larger for the surface which is perpendicular to the direction of pressure of hot-press sintering that than that for the surface which is parallel to the pressure. Although SiC whiskers have no evident effect on friction coefficient of silicon nitride at the above sliding condition, even small contents of SiC whiskers, such as 10 wt percent, reduce considerably the coefficient of friction and show similar frictional characteristics to that of monolithic silicon carbide at the lower sliding speed of 10 mm/min.

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