Mechanical properties of multilayer pvd Ti/TiB2 coatings
Mechanical properties of multilayer pvd Ti/TiB2 coatings
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DOI：
10.1179/026708400101517008
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发表时间：
2000-04
影响因子：
2.8
通讯作者：
M. Berger;M. Larsson
中科院分区：
文献类型：
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作者：
M. Berger;M. Larsson
为了从摩擦学的角度获得共价结合材料（如硼化物和氧化物）的可接受的PVD涂层，必须控制并经常减少涂层生长过程中产生的非常高的压应力，因为这种应力不仅会降低涂层的附着力，还会限制膜的厚度。获得较低应力水平的一种可能方法是利用多层涂层，即在层状结构中将受应力材料与更具延展性的材料结合起来。在本研究中，高应力PVD TiB2材料与韧性Ti层。通过改变多层周期（即一个Ti片层和一个TiB2片层的复合厚度）和两相的片层厚度比，来评价它们对Ti/TiB2涂层的一些重要力学性能和耐磨性的影响。采用磁控溅射法和电子束枪蒸发法制备涂层。采用x射线衍射法评价涂层的相组成。通过纳米压痕（硬度和模量）、梁挠度（残余应力）、划痕测试（内聚性和附着力）和韧窝磨削（磨料耐磨性）来检测其机械和摩擦性能。硬度、杨氏模量、压缩残余应力和磨料耐磨性随涂层中TiB2含量的增加而增加，而在划痕试验中获得的临界法向载荷呈反比关系，即内聚/附着力随TiB2含量的增加而降低。研究表明，结合电子束蒸发Ti和磁控溅射TiB2的混合PVD技术可以制备出比均匀PVD TiB2具有更高断裂韧性、更低残余应力和更高硬度的涂层。还发现Ti的屈服/断裂强度不足，即它不能适应TiB2相产生的应力水平。因此，选择另一种屈服/断裂强度比Ti更高的材料，相信多层涂层的性能可以进一步改善。
To obtain from a tribological perspective acceptable PVD coatings of covalently bonded materials, such as borides and oxides, it is essential to control and often reduce the very high compressive stresses which develop during coating growth, since such stresses not only reduce coating adhesion but also limit film thickness. A possible way to obtain lower stress levels could be to utilise multilayer coatings, that is to combine the stressed material with a more ductile material in a layered structure. In the present study a highly stressed PVD TiB2 material was layered with ductile Ti. The multilayer period, i.e. the combined thickness of one Ti lamella and one TiB2 lamella, and the lamellar thickness ratio of the two phases were varied in order to evaluate their influences on some important mechanical properties and on the abrasive wear resistance of the Ti/TiB2 coatings. The coatings were deposited using magnetron sputtering of TiB2 and electron beam gun evaporation of Ti. To evaluate the coating phase composition X-ray diffraction was used. Mechanical and tribological properties were examined by nanoindentation (hardness and modulus), beam deflection (residual stress), scratch testing (cohesion and adhesion), and dimple grinding (abrasive wear resistance). Hardness, Young's modulus, compressive residual stress, and abrasive wear resistance were found to increase with the fraction of TiB2 in the coatings, and an inverse relation was found for the critical normal load obtained in scratch tests, i.e. cohesion/adhesion decreased with increasing TiB2 fraction. The investigation showed that a hybrid PVD technique combining electron beam evaporation of Ti and magnetron sputtering of TiB2 can be used to produce coatings with increased fracture toughness, decreased residual stress, and relatively high hardness as compared to homogeneous PVD TiB2. It was also found that the yield/fracture strength of Ti was insufficient, i.e. it could not accommodate the level of stress generated in the TiB2 phase. Therefore, by choosing another material with higher yield/fracture strength than Ti it is believed that the properties of the multilayer coating could be improved even further.