纳米复合硬质涂层中非晶组织的控制与致韧机理研究

Hard and super hard coatings require a trade-off between high hardness and high toughness. However the recent research shows that nanocomposite coatings with microstructures comprising of nanocrystalline grains in an amorphous matrix can produce unique combination of both high hardness and toughness. The toughening mechanism based on the nanocomposite structure is still not clear and most of the research focus on the plastic deformation in nanocrystals or the phase boundary between nanocrystals and amorphous phase, leaving the amorphous matrix neglected. As a result, the amorphous matrix designing and controlling remains as a hit-and-miss job. Therefore this research will investigate the toughening mechanism of nanocomposite coatings based on the characteristics of amorphous matrix. A serials of TiN coatings containing amorphous carbon，silicon nitride or boron nitride will be used to examine the deformation mode of the amorphous matrix by in situ observation. A molecular simulated will also be adopted to probe the deformation mechanism of the amorphous matrix. Finally the relationship among the structure and size of the amorphous matrix, the deformation mode of the amorphous matrix and the toughness of the hard coatings will be clarified and a performance optimization will be proposed. Thus this research will not only improve the development of hard and super hard coatings with high toughness, but benefit the interdisciplinary research in material science and theoretical simulation areas.

高硬度与韧性难以兼得是高硬度、超高硬度涂层长期面临的瓶颈问题。现有研究表明构造纳米晶/非晶复合硬质涂层可成为解决这一问题的有效途径。但此类涂层致韧机理尚不明确，且相关研究大多集中在纳米晶、纳米晶与非晶晶界中，导致涂层中非晶的选择、设计和控制具有一定的盲目性。基于此，本项目从非晶的新角度出发，以复合不同类型、不同尺寸非晶的TiN系硬质涂层为研究对象，以涂层中非晶的形变机制为切入点，以原位微区观察和实时原位微区观察为主要研究手段，明晰非晶种类和尺寸等因素对涂层韧性的影响，结合分子动力学计算，探索非晶在纳米复合硬质涂层中的致韧机理，并在此基础上提出纳米复合硬质涂层性能（硬度和韧性）优化综合策略。这不仅对推进我国高硬高韧涂层的发展具有重大现实意义，且将促进材料学和理论数值模拟的相互交叉渗透发展，丰富相关研究邻域的基础理论，具有重大学术价值。

本文通过磁控溅射方法，制备了非晶SiNx、非晶C、TiN、TiCN、TiAlN、TiAlCN、 CrSiN和TiSiN系列涂层，研究了各工艺参数（功率、偏压、氮流量和时间等）和沉积手段（多层沉积工艺、共沉积工艺）对上述涂层成分和结构的影响，通过XRD、SEM、TEM、XPS、显微硬度计、纳米压痕仪等手段对薄膜微观结构、力学性能（硬度、弹性模量、韧性、摩擦系数）进行了表征。同时利用计算机模拟技术对薄膜在纳米压痕条件下的形变过程进行了模拟。.试验结果表明：（1）利用功率、偏压、氮流量和时间等工艺参数可以对薄膜结构（厚度、晶体取向和各相分布）进行有效调控。（2）压应力是薄膜增韧的重要影响因素，单相薄膜厚度同韧性有一定相关性。具有非晶碳相的纳米复合TiCN薄膜以及TiAlCN薄膜具有良好的韧性。TiAlCN薄膜还呈现大于40GPa的超硬性能。（3）计算机模拟表明纳米压痕条件下层状、柱状和三维复合TiN/SiN涂层的最大应力区域可以被第二相分割碎化，甚至降低，这有利于抑制裂纹扩展，从而提高薄膜韧性。相对TiN相，非晶SiNx加载条件下承受更大的应力，更易开裂诱发失效。因此减小非晶尺寸有利于抑制非晶相裂纹灾难性扩展，达到薄膜增韧效果.