采用反应溅射方法制备了一系列具有不同Si3N4层厚度的VAlN/Si3N4纳米多层涂层,并对涂层的微观结构和力学性能进行了研究.结果表明,厚度较小(~0.4 nm)的Si3N4结晶与VAlN相干生长,与VAlN单层涂层相比,硬度显着增加.相干VAlN/Si3N4纳米多层涂层的硬度高达48.7 GPa.随着Si3N4层的进一步加厚,纳米多层的相干生长终止,在纳米多层中形成非晶结构,从而硬度下降.另一方面,当Si3N4层厚为0.4 nm时,VAlN/Si3N4纳米多层涂层的摩擦系数几乎等于VAlN单层涂层的摩擦系数,这归因于Si3N4的结晶以及在VAlN和Si3N4中纳米多层涂层的硬化效果.随着Si3N4层的进一步增厚,观察到VAlN/Si3N4纳米多层涂层的摩擦系数显着提高.
VAlN coating is of particular interest for dry cutting applications owing to its low-friction and excellent abrasiveness. Nano-multilayer structure is designed to tailor the properties of VAlN coating. In this work, a series of VAlN/Si3N4 nano-multilayer coatings with varied Si3N4 layer thicknesses were prepared by reactive sputtering method. The microstructure and mechanical properties of the coatings were both investigated. It is revealed that Si3N4 with a shallow thickness (~0.4 nm) was crystallized and grown coherently with VAlN, showing a remarkable increase in hardness compared to VAlN monolayer coating. The hardness of coherently VAlN/Si3N4 nano-multilayer coatings reached to 48.7 GPa. With further increase of Si3N4 layer thickness, the coherent growth of nano-multilayers was terminated, showing amorphous structure formed in nano-multilayers and the hardness was declined. On the other hand, when Si3N4 layer thickness was 0.4 nm, the friction coefficient of VAlN/Si3N4 nano-multilayer coating was almost equal to that of VAlN monolayer coating, which was attributed to the crystallization of Si3N4 and the produced coherent interfaces between VAlN and Si3N4 for the hardening effect of nano-multilayer coatings. Upon further increase of Si3N4 layer thickness, pronounced improvement of friction coefficient in VAlN/Si3N4 nano-multilayer coating was observed.