硬质高韧纳米复合涂层中"软相"的控制及韧化机制研究

Low toughness is a key problem restricting the use of hard coatings. The recent research shows that nanocomposite coatings comprising of hard and soft phase can produce unique combination of both high hardness and toughness. But the control of soft phase and its toughening effect in such coatings are still explored. The toughening mechanism is still not clear, and related studies are focused on the evaluation and characterization of the coating toughness, resulting in the lack of effective guidance of the design of nanocomposite coatings. Therefore, this research will investigate the toughening mechanism of nanocomposite coatings based on the plastic deformation. A serials of nanocomposite coatings composed of soft metals are prepared. The relation between the content of soft metals, coating microstructure and plastic deformation is studied. And the coatings will also be used to examine the deformation mode in situ observation. A molecular simulated will also be adopted to probe the deformation mechanism of nanocomposite coatings containing soft phase. Finally, the toughening mechanism of hard coatings will be clarified and the design of hard and tough coatings will be proposed. Thus this research will not only improve the development of hard and super hard coatings with high toughness, but also benefit the interdisciplinary research in material science, mechnics, nanoscience, and surface science. It has an important academic value.

韧性差是限制硬质涂层使用的关键问题。现有研究表明，构造"硬相+软相"纳米复合结构可以有效解决这一问题。但该类涂层中对"软相"的控制及其韧化作用的认识尚在探讨之中，致韧机理不明，且相关研究大多集中在涂层韧性评价和表征上，导致纳米复合涂层结构的设计及控制缺乏有效的指导。基于此，本项目拟以涂层塑性变形为切入点，以复合软金属的硬质涂层为研究对象，以软相含量、纳米复合结构与涂层塑性变形行为之间的关系为中心，以原位微区观察为主要研究手段，研究软相对纳米复合涂层变形行为的影响，并结合分子动力学模拟，探索"硬相+软相"纳米复合涂层的致韧机理，提出硬质高韧涂层设计指导思想。这不仅对硬质高韧纳米复合涂层材料的发展有着重大的现实意义，而且促进材料科学、力学、纳米科学和表面科学之间的交叉渗透，丰富相关领域的基础理论，具有重要学术价值。

具有“硬相+软相” 纳米复合结构的涂层可以兼有硬质高韧的特点，但该类涂层中对“软相”的控制及其硬韧化机制尚在探讨之中。本项目系统研究了软金属铜和镍对硬质CrN涂层的影响，探讨了软金属种类、含量、存在形式以及分布、磁控溅射方法、工艺参数等对纳米复合涂层组织和性能的影响。结果表明，溅射功率和基底偏压对两种纯金属涂层的组织结构（生长取向、组织形貌、晶粒大小等）和性能（硬度、接触刚度、弹性模量和韧性）影响规律并不一致，因此软金属种类对纳米复合涂层的作用亦不同。对于铜掺杂的纳米复合涂层，射频条件下，超低铜量的掺杂可以提高涂层硬度，但不能改善韧性，也不能明显细化晶粒，而双靶共溅条件下，铜的加入不仅可以细化晶粒，提高硬度，还能改善韧性。对于镍掺杂的纳米复合涂层，不管是射频还是双靶共溅条件下，均不能细化晶粒。前者中镍的添加可以提高硬度和韧性，但过多镍会使硬度下降。后者中镍的添加使涂层硬度、弹性模量和韧性都先升高后略下降。可见，恒定偏压下，不论哪种软金属掺杂，不管硬质相能否被细化，软金属对硬质相的包裹率越大，涂层韧性越高，但涂层硬度不仅受软金属包裹率的影响，还受涂层生长取向、点阵畸变、硬质相晶粒尺寸及应力大小等的共同影响，更为复杂。上述研究成果不仅为硬质高韧纳米复合涂层的设计提供了指导，还对其发展有着重大意义。