| Boron carbide is a kind of special ceramics with outstanding properties used in a wide range of industrial applications. One of its very important applications is as gas bearing material in gyro motor. It has been found that the tribology property of boron carbide is the key influencing factor of life-span and precision of gas bearing. The research has worked comprehensively and deeply on the friction and wear characteristics of boron carbide self-mated pair. Through the research, the tribology behavior of boron carbide self-mated pair and its self-lubricant mechanism have been learned basically. Furthermore, an effective method of decreasing the friction coefficient of boron carbide self-mated pair is proposed. The results acquired will play a positive role in raising the life-span and precision of the gas bearing, and in promoting and extending the application of boron carbide in aviation, aerospace and navigation. In the paper, the means of nano tribology is employed preliminarily for investigation of the micro-tribological behavior of boron carbide ceramic, which perfects and enriches the content of nano tribology research system. For the sake of boron carbide matrix ceramics can be used as anti-friction material, the research has conducted the relatively systematic study on the friction and wear feature of B4C-SiC self-mated and B4C, B4C-SiC 45* steel-mated pairs.It was fabricated ultra-fine boron carbide powder whose particle size was less than lum and whose properties conformed to GB5151-85-HTP-1 need. The B4C and B4C-SiC ceramics used in the study were fabricated by a hot-pressing method. The properties of the hot-pressed pure B4C ceramic, such as its average grain size less than lum, relative density more than 99%, bending strength 510-520 MPa, Knoop hardness 29.5-30 GPa, had reached the lead level worldwide.An apparatus as a tribometer was designed, according to the condition as the boron carbide used in the gas bearing. The ring-on-ring friction couple was applied. The specimen was easy to be prepared by hot-pressing since its shape was simple. At the tribometer, the average sliding velocity and load could be changed in a wide range. The theory relative error of friction coefficient measured by the tribometer was less than 1.6%.The research pioneered the first attempt in studying the friction and wear characteristics of B*C self-mated pair. The effects of sliding distance, normal load and sliding velocity on the friction coefficient had been investigated. The results showed that friction coefficient decreasing gradually with sliding distance to a certain value and increasing normal load and sliding velocity were beneficial to the decrease of the friction coefficient. It had been found that during sliding E^Os/HsBCb lubricant film presented on the friction surface on account of tribochemical reaction. Mechanistically, it was proposed that the low friction was due to the layered crystal structure of HsBOs. And the investigation of the wear of 640 self-mated pair indicated that its wear form belonged to chemical wear, the wear rate was 5.1 X 10'7 -8.3 X 1(T7 mm3-(N-m)''.The research proposed firstly that pre-oxidization could lower the friction coefficient of B4C self-mated pair. The effects of the pre-oxidization factors, such as pre-oxidization temperature and pre-oxidization time, on the friction coefficient were investigated. The results showed that the pre-oxidization temperature should not go beyond 1 273 K and pre-oxidization time lasting 0.5-1.0 h was suitable. The friction coefficient of B*C self-mated pair pre-oxidized 1 h at 1 073 K was as low as 0.04-0.05, compared to that of 840 self-mated pair without pre-oxidization as high as 0.2-0.3. The lubricant film produced on the friction surface was stable enough at experimental condition.Tribology behavior of B4C-SiC self-mated pair and of B4C-SiC mated by 45* steel pair were investigated. The results showed that the friction coefficients, as well as wear rates, of B4C-SiC self-mated pair increased with the SiC content of the...
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