摘要
在SiC基体中,用TiC和B4C为原料采用固相反应原理原位合成了高温自润滑TiB2-SiC基复相陶瓷,提高了SiC陶瓷高温摩擦学性能;高温摩擦氧化是TiB2-SiC/TiB2-SiC高温自润滑的主要机制。试样磨损断面氧化层和过渡层接触紧密;摩擦表面具有塑性变形性能,由脆性体向塑性体或者弹塑性体过渡。复相陶瓷中TiB2颗粒产生的“钉扎效应”,导致裂纹扩展路径偏转,改变了应力场的分布特性,降低了微裂纹尖端应力场强度,提高了裂纹扩展门槛值。TiB2-SiC磨损中存在断裂力学上的(Ⅰ+Ⅱ)型和(Ⅰ+Ⅲ)复合裂纹非平面扩展,以及裂纹尖端微小塑性屈服区的存在,使得裂纹扩展门槛值在“极限上值”和“极限下值”间随着裂纹扩展实际有效长度的变化而动态变化,导致材料延迟断裂。
On the basis of SiC, a solid reaction was developed to generate TiB2 and TiB2 （25 % weight）-SiC matrix composites with self-lubrication at elevated temperature, which are compounded by in-situ synthesis with TiC,B4C and SiC as raw material. This method improves the tribological characteristics of SiC at elevated temperature. The tribo-oxidization at elevated temperature is the dominating mechanism to self-lubrication of TiB2-SiC/TiB2-SiC. The oxidizing layer and the transitional layer of the wore surface＇ s cross-section of test sample contact closely. The wore surface has the property of plastic deformation and may transit from brittle state to plastic or elastic state. The ＂Pin Effect＂ exhibited by TiB2 particles in TiB2-SiC matrix composites causes the crack extension route to deflect. Concomitantly the stress distribution is altered, the stress of slight crack frontier is lowered, and ＂the threshold value＂ of crack extension is raised. The complex crack of type （ Ⅰ ＋Ⅱ ） and （ Ⅰ ＋ Ⅲ） in fracture, which is existent during wearing, expands non-flatly. Besides, fine yield deformation zone exists at crack frontier. The above two factors cause the crack expansion ＂threshold value＂ to fluctuate dynamically from ＂upper bound value＂ to ＂lower bound value＂ in accordance with the change of valid length of actual crack expansion. Resultantly, the fracture of composites is delayed.
出处
《润滑与密封》
CAS
CSCD
北大核心
2007年第7期59-65,共7页
Lubrication Engineering
基金
国家自然科学基金项目(50174024)
上海宝钢资助项目.
