SiO_2对摩擦第三体形成的作用

Effects of SiO_2 on the formation of third bodies in friction

采用粉末冶金技术制备Cu-SiO_2烧结材料,研究了Cu-SiO_2摩擦表面上的SiO_2颗粒与摩擦第三体的关系.结果表明,在摩擦中Cu-SiO_2中的SiO_2颗粒起钉扎点的作用,阻止第三体颗粒的运动,形成第三体塞积区,第三体的塞积面积和存在周期取决于SiO_2颗粒的承载能力,SiO_2颗粒的破损使第三体塞积区分解.第三体塞积区经历—个塞积-覆盖-分解-再塞积-再覆盖的过程;粘着性好的第三体充填到碎裂的SiO_2裂纹中,对SiO_2有夹持和覆盖的作用,有利于阻止碎裂的SiO_2进一步剥落.随着SiO_2含量的增加,起犁削作用的硬质点数增加,使摩擦系数提高;摩擦速度的提高伴随着温度的升高,容易形成连续而致密的第三体,有利于稳定摩擦系数;随着摩擦速度的降低,第三体疏松而不连续,容易脱离摩擦面而增大磨损量.

Sintered Cu-SiO2 composites were prepared through powder metallurgy method and the relationship of the SiO2 particles and the third bodies was investigated on a pin-on-disk tester in the friction speed range of 7.8-47 m/s. The results demonstrated that the SiO2 particles in the material acted as anchoring points, blocking the movement of the third bodies and resulting in regions of third body compact. The area and duration of such third body compact depended on the strength of the SiO2 particles. The compact zone of third body broke up when the SiO2 particles broke down. The compact zones of third body went through the process of blocking-covering-breaking-blocking again-covering again. When filling into the cracks of the damaged SiO2, the adhesive third bodies had gripping effects on the SiO2, thus preventing further peeling off of the broken SiO2. As the SiO2 content increased, the friction coefficient rose due to the increase in the number of hard points with plowing effect. Increase in friction speed, accompanied by the elevation in friction temperature as a result, promoted the formation of compact and continuous third bodies, and was therefore beneficial to the stabilizing of the friction coefficient. On the contrary, low friction speed exacerbated wear because the third bodies formed at low friction speed were porous, discontinuous and consequently easy to peel off from the friction surface.