多层结构对Ti/TiN涂层性能的影响

Effect of multilayered structure on the properties of Ti/TiN coating

摘要:

以TiN、TiAlN为主的过渡族金属氮化物硬质涂层以其较高的表面硬度、良好的耐磨以及抗高温氧化性能，被广泛应用于材料表面防护涂层。然而，涂层内部积聚的高内应力却容易易引发起涂层与基体的结合力问题。利用PVD技术很难在材料表面制备出厚度超过10微米的TiN或TiAlN涂层。多层复合结构能够有效控制涂层中的应力分布，从而使得其成为获得较厚硬质涂层的一种有效方法。本文在TC4合金以及Si（100）基体上利用等离子增强离子镀技术制备了具有不同复合层数的多层Ti/TiN涂层，并研究了复合层数对涂层力学性能的影响。结果表明，随着复合层数的增加，涂层的各项力学性能得到了显著强化。涂层的显微硬度高达2750HV，厚度大于50微米，且具有较好的韧性。涂层的韧性与显微硬度成正比例关系。同时，48层复合结构的Ti/TiN涂层具有低于0.35的摩擦系数以及最佳的抗磨损性能。然而，随着复合层数的进一步增加，涂层与基体的界面显著弱化了涂层的结合强度。

Abstract:

Metal nitride hard coatings, such as TiN and TiAlN, were widely used to protect materials because of their higher hardness and wearing properties. However, these coatings always contain a high degree of internal stress which could arouse adhesion problems. It’s hard to synthesize monolayer TiN or TiAlN coatings thicker than 10μm by PVD method. The multilayer composite structure, offering an efficient way of controlling residual stress, is an effective way to synthesize thicker hard coatings. In this study, a series of multilayer composite Ti/TiN coatings with different composite periods were synthesized by plasma enhanced ion plating and how the multilayered structure affects the coating’s mechanical properties was studied in detail. The result shows that the coating’s mechanical properties are strengthened as increasing the periods of composite Ti/TiN layer. The micro hardness can reach to about 2750HV0.25 albeit possessing better toughness and higher thickness (i.e.>50?m). The coating’s toughness is almost direct proportional to hardness. And also the coating’s tribological performance is improved with a lower dry friction coefficient (about 0.35) and higher wearing resistance by alternating 48 periods of Ti/TiN layer. However, the coating’s bonding strength is weakened as increasing the period of Ti/TiN layer blindly due to the weak interface of coating and substrate.