Si掺杂构筑拉/压应力层间耦合结构对WBCSi多层涂层的性能影响和机理研究

To solve the key problem of the high compressive stress and low thickness for the transition-metal boride coating (TmBx), which has been a competitive candidate as a tool coating for nonferrous metals and their alloys processing because of their high hardness, self-lubrication and non-stick properties. In this study, the preparation and mechanism research of the low-stress, high-performance and thick WBCSi coatings (>5μm) will be investigated systematically via the architecture of the tensile stress/compressive stress alternant structure by Si-doping. By adjusting the Si content, the sing-layer WBCSi coating with different stress types will be obtained using the magnetron sputtering technique. Then by changing the Si content periodically in the coatings, different tensile stress/compressive stress alternant structures will be built for the multilayered WBCSi coatings. The microstructure of the coatings with different Si content will be studied to reveal the mechanism of the residual stress evolution caused by Si-doping. To build the relationship among the film structure, residual stress, film thickness and the related properties, the influence of the tensile stress/compressive stress alternant structure by Si-doping on the structure evolution and properties (hardness, wear-resistance and thermal stability) of the multilayered WBCSi coatings will be investigated in detail. Combined with the finite-element method, the deformation behavior between the tensile layer and the compressive layer by some external force can be revealed, and the functional mechanism of the tensile stress/compressive stress alternant structure affecting the coating superior performance can be obtained. The results of this research will be expected to provide a scientific basis and theoretical guidance for the stress and thickness regulation of the transition-metal boride coatings. It can also be used to guide the structure design and preparation of the other multilayered coatings with high thickness, low stress and excellent performance.

过渡族金属硼化物涂层(TmBx)因高硬度、自润滑及不粘刀特性在有色金属及其合金的精加工领域展现出广阔应用前景，但高内应力低厚度是其面临的核心难题。本项目以WBCSi涂层为研究对象，借助Si掺杂构筑拉/压应力层间耦合结构的思路实现高性能、低应力厚WBCSi涂层（>5μm）的可控沉积。采用磁控溅射法通过Si掺杂调控WBCSi涂层的应力类型，调整工艺使Si周期性分布获得拉/压应力层间耦合结构的WBCSi多层涂层。系统研究涂层的组织结构、力学性能、摩擦学行为和热稳定性，获得Si掺杂对TmBC涂层应力的调控机制，揭示应力层间耦合结构对涂层应力、厚度及各项性能的影响规律，结合有限元分析获得涂层在外力作用下的层间耦合行为及其层结构依赖性，阐明WBCSi多层涂层具备优异综合性能的内在机理。研究成果将为解决TmBx涂层的高应力低厚度问题提供理论基础和技术支持，同时对其他多层涂层的结构设计和制备具有指导意义。

过渡族金属硼化物(TMBx)因高硬度、自润滑及不粘刀特性在有色金属及其合金的精加工领域展现出广阔应用前景，但高内应力、低厚度难以满足涂层的长寿命需求。针对此问题，本项目采用磁控溅射技术，基于不同应力层间耦合结构的设计理念，通过Si周期性分布设计制备了低应力WBCSi硬质涂层，并系统研究了Si掺杂对WBCSi涂层应力、力学和摩擦学性能的调控机理，以及不同应力层间耦合结构对涂层整体应力、厚度及力学和摩擦学等性能的影响规律及作用机制。研究结果表明，涂层结构、Si的存在形式及化学键合是影响WBCSi涂层残余应力的主要因素：对于结晶WBCSi涂层，Si以非晶WSi2和SiC偏析于晶界附近，减少了C-C键，形成了WB2/a-WSi2、WB2/a-WSi2/a-SiC纳米复合结构，降低了WBCSi涂层的残余压应力，并提高了涂层力学和摩擦学性能；对于非晶WBCSi涂层，涂层短程有序度的降低及a-WSi2和a-SiC的生成使涂层的残余压应力大幅降低，力学性能符合混合法则。在上述结果下，设计制备了不同应力层间耦合结构的低应力WBCSi和WB2多层涂层，结果表明各亚层结构、残余应力和厚度是影响多层涂层应力的关键，当涂层的膜/基体系及各亚层之间的弹性模量相差较小且各亚层的微观结构相近时，多层涂层的残余应力可根据各亚层的应力及厚度进行估算，且估算值与实际值接近，否则在界面应力、层间热应力及界面扩散的共同作用下，估算值与实际值存在较大偏差；对于应力层间耦合结构的多层涂层，其力学和摩擦学性能遵循复合法则，但涂层在外力作用下的层间耦合行为及其层结构依赖性有显著区别，即在拉/压耦合、压/拉耦合及压/压耦合结构中，拉/压应力层耦合结构（打底层和最顶层为拉应力层）表现出较差的力学和摩擦学性能。上述研究结果可为发展低应力高厚度TMBx涂层提供理论基础和技术支持，对其它高性能硬质涂层的设计制备具有指导意义。