原位合成碳化硅-硼化钛复相陶瓷的高温摩擦性能及其磨损机理

以SiC为基体,用TiC和B4C为原料反应生成TiB2,原位合成了SiC-TiB2复相陶瓷.通过测试SiC和SiC-TiB2的高温摩擦系数和比磨损率与温度、外加载荷的关系,研究了SiC-TiB2复相陶瓷的高温摩擦学性能.在空气中,外加载荷为0.2 MPa,摩擦速度为0.3 m/s时,SiC-TiB2复相陶瓷自对偶(SiC-TiB2/SiC-TiB2)高温摩擦呈现较好的高温自润滑性能.温度对SiC-TiB2/SiC-TiB2摩擦系数和比磨损率的影响与载荷有关.载荷为0.4 MPa时,比磨损率最大.用X射线衍射测试了SiC-TiB2/SiC-TiB2磨屑的组成,用扫描电子镜观察了SiC-TiB2/SiC-TiB2磨损断面,发现高温摩擦氧化是TiB2-SiC/SiC-TiB2磨损的主要机理.磨损断面包含摩擦氧化层、过渡层和基体亚表面3层,氧化层和过渡层接触紧密.磨屑具有典型包裹结构,其主要氧化物是无定形氧化硅.平滑的氧化层改进了摩擦表面的塑变性能,缓冲了摩擦应力,减小了高温比磨损率.

TRIBOLOGICAL CHARACTERISTICS AND WEAR MECHANISMS OF SILICON CARBIDE- TITANIUM DIBORIDE COMPOSITES BY IN-SITU SYNTHESIS AT ELEVATED TEMPERATURE

SiCTiB_2 composites with TiC and B_4C as raw materials were obtained by in-situ synthesis on the basis of SiC.Tribological characteristics of SiC and SiCTiB_2 at elevated temperature were investigated by testing the fraction coefficient and specific wear rate at different temperatures and different pressures.For the self-mated pairs of SiCTiB_2(SiCTiB_2/SiCTiB_2),the self-lubrication characteristic is good at elevated temperature in the air with a contact pressure of 0.2 MPa,and at a sliding velocity of 0.3 m/s.The impacts of temperature on friction coefficients and specific wear rates of self-mated pairs of(SiC)TiB_2 depend on the contact pressure.The maximum specific wear rate is obtained at the contact pressure of 0.4 MPa.The components in the worn debris of SiCTiB_2/SiCTiB_2 were determined by X-ray diffraction,and the worn cross-section of SiCTiB_2/SiCTiB_2 were observed by scanning electron microscope,the tribo-oxidization at elevated temperature is the dominant wear mechanism of SiCTiB_2/SiCTiB_2.The worn cross-section of the sample includes an oxide thin film,a transitional layer and the sub-surface of the matrix,among which the oxide thin film and transitional layer of SiCTiB_2 composites contact with each other closely,the worn debris has a typical parcel structure and the major oxide is amorphous silica.The smooth oxidation layer improves the plastic deformation of the contact surface,decreases the frictional stress,and reduces the specific wear rate of SiCTiB_2/SiCTiB_2.