Environmental SEM tribometry of the pressureless-sintered Hexoloy alpha-SiC ceramics was continued in 0.2 and 3.4 Torr partial pressures of oxygen (Po2) at room temperature (RT) to 95O deg C, coupled with after-test SEM photomicrography and AES/XPS surface analyses of the wear scars and the adjacent (unused) surfaces. The results show some correlation in the somewhat improved friction behavior of both the previously tested CERCOM SiC-B in partial pressures of oxygen compared to vacuum, especially when the slower tribo-oxidation kinetics and the surface-oxide-induced reduction in grain pull-out of the boron/carbon-pressed Hexoloy are taken into account. Even in the presence of the thickest lubricating film formed at the 3.4 Torr PO2, the COF still did not become reduced below -0.2 (and the MAX.COF below 0.3). These values are an order-of-magnitude higher than those of the polished PCD. The same observation was made with the SiC-beta previously. The wear rate of Hexoloy is only slightly (albeit consistently) less in oxygen than that of the SiC-beta, with both in the 10(-15)m3/N x m range (an order-of-magnitude greater than PCD). Considering the overall tribological behavior of both alpha-SiC materials, neither is able to serve better than PCD in MEMS moving mechanical assembly applications intended for extreme environments.