Development of atmosphere controlled Tribotester and evaluation of tribological properties of hard thin films nanostructured with femtosecond laser

研究了飞秒激光对类金刚石薄膜表面进行纳米化处理后的摩擦学性能。一个广泛的区域上的DLC表面纳米结构使用精确的目标扫描系统开发的FS-激光加工。在本实验中，我们开发了两种类型的激光扫描。一种是平行扫描，以产生均匀的纳米结构表面。另一种是沿着网状图案交叉扫描，以在表面上形成部分纳米结构化区域。所得结果总结如下：1）在15 x 15 mm^2的面积上，纳米结构均匀地形成在DLC表面上。2）在接近烧蚀阈值的E = 110 μJ处，结构化表面被均匀地改性为GC层。3）结构化DLC膜的摩擦系数对于钢球显示出小的降低，而对于陶瓷WC-Co球显示出小的增加。4）在纳米结构类金刚石膜表面涂覆MoS_2层，可显著提高其摩擦系数。用钢球和WC-Co球测得的表面摩擦系数μ分别为0.07和0.02 - 0.04。5）通过交叉扫描产生的烧蚀区的网状图案产生了增加μ的有效方法，6）纳米压痕试验和纳米划痕试验（100 μ N ~ 2000μN）的摩擦学试验表明，激光处理后的DLC膜表面改性为GC后，表面层变得柔软，摩擦系数比未处理的DLC膜增加。

We report tribological properties of diamond-like carbon (DLC) film of which surface has been nanostructured with femtosecond (fs) laser pulses. A broad area on the DLC surface was nanostructured using a precise target-scan system developed for the fs-laser processing. In the present experiment we have developed two types of laser scan. One is a parallel scan to produce a uniformly nanostructured surface. The other is a crossed scan along a net-like pattern to form a partially nanostructured area on the surface. The results obtained are summarized as follows.1)The nanostructure has been formed uniformly on the DLC surface over the area of 15 x 15 mm^2.2)The structured surface at E = 110 μJ near the ablation threshold is uniformly modified to the GC layer.3)The friction coefficient of the structured DLC film has shown a small decrease for the steel ball but a small increase for the ceramic WC-Co ball.4)A large improvement of the friction coefficient of the DLC surface has been achieved by coating the MoS_2 layer on the nanostructured DLC surface. The measured friction coefficients μ of the surface were 0.07 with the steel ball and 0.02 - 0.04 with the WC-Co ball.5)The net-like patterning of the ablated zone created by the crossed scan produces an effective method to increase μ, maintaining the initial surface flatness.6)The nano-indentation test and nano-scratch test(100〜2000μN) indicate that the laser-treated surface layer modified to GC becomes soft and its friction coefficient increases as compared with that of the untreated DLC.