转速对水环境下纯铜滚动载流摩擦损伤的影响

使用滚动载流摩擦试验机研究了水环境下转速对纯铜滚动载流摩擦性能和表面损伤的影响. 转速从30 r/min增至480 r/min，水下摩擦系数从1.06降低至0.49，且水下摩擦系数远高于干态摩擦系数；水下接触电阻从0.57 Ω升高至6.4 Ω，且水下接触电阻比干态下更高. 分析可能的机制如下:低转速时水主要表现出毛细作用，导致摩擦系数较高，材料表面发生明显的层片状剥落；高转速时水体现出部分润滑作用，摩擦系数降低，但“水压”作用导致材料表面发生疲劳剥落. 不同转速下疲劳损伤形式转变是摩擦系数降低和水压作用增强竞争的结果. 本文试验条件下表面损伤形式转变的临界转速在200~240 r/min之间. 载流摩擦表面发生了电化学氧化，但由于低转速表面剥落严重，导致表面O: Cu原子个数比较低，接触电阻较低. 

Effect of Rotating Speed on Surface Damage of Rolling Current-Carrying Pairs in a Water Environment

The effect of rotating speed on the current-carrying properties and surface damage of pure copper rolling pairs were investigated in a water environment. With the increasing of rotation speed from 30 r/min to 480 r/min, the friction coefficient decreased from 1.06 to 0.49 in water environment, which was much higher than that of dry current-carrying friction. And the underwater contact resistance increased from 0.57 Ω to 6.4 Ω, which was higher than that in dry rolling. The possible mechanisms were as follows. At low speeds, the water mainly exhibited capillary action, resulting in a high coefficient of friction and significant flaking on the surface of the material. While at high speeds, water exhibited partial lubrication effect, the coefficient of friction decreased and pitting occurred on the surface because of the pressurization effect. The evolution of the damage characters was based on the competition of the lubrication and pressurization of water, and the critical rotation speed of such transition was 200~240 r/min. Electrochemical oxidation happened on the current-carrying friction surface, but the atomic ratio of O to Cu was lower at lower speed due to the severe peeling, and therefore the contact resistance was lower.