Nano-mechano-electrochemistry of Passive Metal Surfaces

在溶液中进行纳米压痕和纳米划痕试验，原位评价钝化单晶铁和多晶钛表面的机械电化学性能电化学控制在pH 8.4的硼酸盐溶液。钝化金属表面在溶液中的硬度和摩擦系数可以分别从纳米压痕试验测量的载荷-深度曲线和纳米划痕试验测量的侧向力曲线确定。钝化铁（110）表面的硬度大于钝化铁（100）表面的硬度，而（110）表面的摩擦系数小于（100）表面的摩擦系数。铬酸盐处理提高了铁（110）和铁（100）表面的硬度，在5 V电化学控制下的纳米压痕和纳米划痕处理得到的钛表面的硬度和摩擦系数显著高于相同条件下阳极氧化后空气中纳米压痕和纳米划痕处理得到的钛表面的硬度和摩擦系数。溶液中硬度和摩擦系数的大值归因于在5 V电化学控制下阳极氧化膜破裂处的高再钝化速率。

Nano-indentation and nao-scratching tests in solution were performed for in-situ evaluation of the mechano-electrochemical properties of passive single crystal iron and polycrystalline titanium surfaces electrochemically controlled in pH 8.4 borate solution. The hardness and friction coefficient of passive metal surfaces in solution could be determined from the load-depth curves measured with nano-indentation tests and from the lateral force curves measured with nano-scratching test, respectively. The hardness of the passive iron (110) surface was larger than that of the passive iron (100) surface, while the friction coefficient of the (110) surface was less than that of the (100) surface. The chromate treatment increased the hardness of both iron (110) and (100) surfaces.The hardness and friction coefficient of the titanium surface obtained with nano-indentation and nano-scratching under the electrochemical control at 5 V were significantly larger than those of the titanium surface obtained with nano-indentation and nano-scratching in air after anodic oxidation at the same condition. The large values of hardness and friction coefficient in solution were attributed to high repassivation rate at the ruptured sites of anodic oxide film under the electrochemical control at 5 V.