深冷处理对GLC多层薄膜界面结构及结合强度的影响

Effects of Cryogenic Treatment on Interface Structure and Bonding Strength of GLC Multilayer Films

为了研究深冷处理后GLC多层薄膜界面结构及结合强度的变化,采用非平衡直流磁控溅射技术,在W9高速钢上沉积了含GLC功能层、Cr/C梯度层及Cr底层的类石墨碳多层薄膜,厚度约为4μm。采用液氮(-197℃)对GLC/高速钢复合体系进行深冷处理,借助XPS、SEM及TEM表征了GLC薄膜的表面、断面结构及界面微观组织;采用洛氏硬度仪定性考察了薄膜的膜基结合强度。结果表明:复合体系经深冷处理后除基体的硬度及承载能力得以提高外,多层膜各层及基体中裂纹的萌生及传播受到抑制,界面结合强度明显增强。其作用机理在于深冷处理后,Cr底层的柱状晶结构被"打破",纤维状结构消除,组织更加致密均匀;同时,Cr/C梯度层中Cr晶粒碎化平均尺寸由20 nm减小为5 nm,达到细晶强化效果。因此,膜基及层间界面结构得以改善,界面失配减小,基体及多层膜各层间的变形协调性能增强。

In order to investigate the changes of interface structure and bonding strength of GLC multilayer films after cryogenic treatment, GLC multilayer films of 4 μm thickness were deposited on W9 high-speed steel by unbalanced magnetron sputtering technique, which were composed of GLC functional layer, Cr/C gradient layer and Cr bottom layer. GLC films/high-speed steel compound systems were cryogenically treated in the liquid nitrogen（-197 ℃）. The surface, cross section morphologies and interface microtopographies of the film/substrate were analyzed by XPS, SEM and TEM. Rockwell hardness tester was used to test the film-substrate bonding strength. The results show that the hardness and carry capacity of the substrate is improved by cryogenic treatment of the compound system, initiation and propagation of cracks in each layer of the multilayer film and the substrate are also restrained, and the interracial bonding strength is obviously enhanced. Further analysis shows that the columnar crystal structure in the Cr bottom layer is broken after cryogenic treatment, and the fibrous structure is eliminated; therefore, its organization becomes more dense and homogeneous. Meanwhile, the Cr grain fragmented average size of the Cr/C gradient layer is reduced from 20 nm to 5 nm, thus achieves the effects of fine-grain strengthening. Therefore, the interface structure between each layer and the substrate is improved and the interface mismatch is reduced; which greatly improves the deformation coordination performance of the film and the substrate.