TiN/TaN多层膜的结构和摩擦学性能

Structures and Tribological Properties of TiN/TaN Multilayer Coatings Deposited on Silicon Wafer by Magnetron Sputtering

利用磁控溅射法在单晶硅基底上制备了一系列TiN/TaN多层膜;采用X射线衍射仪、显微硬度计、球-盘摩擦磨损试验机和三维表面形貌仪等分析了多层膜的结构、硬度、摩擦学性能和磨损机制.结果表明:所制备的多层膜具有良好的周期性和清晰的界面结构,其中TiN层具有面心立方结构,当TaN层在调制周期Λ值小于8.5nm时具有面心立方结构,在调制周期Λ值大于8.5nm时具有部分六方结构;多层膜的硬度受调制周期影响,当调制周期Λ值为8.5nm时,显微硬度达到最大值31.5GPa.相对于TiN薄膜而言,TiN/TaN多层膜的摩擦系数较高、耐磨性能更好;多层膜的磨损机制主要为犁削、粘着和局部剥落.

TiN/TaN multilayer coatings consisting of alternate nanometer-scale TiN and TaN layers were deposited on single crystal Si substrates making use of magnetron sputtering technology. The hardness of the resulting TiN/TaN multiplayer coatings was measured. Their structures were analyzed by means of X-ray diffraction, scanning electron microscopy, and 3-D surface profilometry. The friction and wear behaviors of the TiN/TaN multilayer coatings sliding against AISI1045 steel in a pin-on-disc contact mode under unlubricated conditions were evaluated. The wear mechanisms of the composite coatings were discussed based on the analyses of the worn coating surfaces using a scanning electron microscope equipped with an energy dispersive X-ray analyzer attachment and a 3-D surface profilometer. It was found that the TiN/TaN coatings had good modulation periodicity and sharp interface between the TiN and TaN layers. The TiN layer had a cubic structure, but a hexagonal structure emerged from the cubic TaN layer at a modulation period above 8.5 nm. The microhardness, microstructures, and tribological behaviors of the TiN/TaN coatings were closely related to the modulation period. Namely, the TiN/TaN coating deposited at a modulation period of 8.5 nm had the maximum hardness of 31.5 GPa, which was significantly larger than that of the monophase TiN or TaN coating. This was attributed to the hardening effect and superhardening effect of the composite coatings. Subsequently, the TiN/TaN coatings had larger friction coefficients but much better wear resistance than TiN coating. Moreover, the TiN/TaN coatings were dominated by ploughing, adhesion, and local spalling, as they slid against the steel in unlubricated conditions.