纳米晶NiSi2/Ti5Si3复合涂层耐磨耐蚀性能研究

Investigation on Wear and Corrosion Resistance Behaviors of Nano-crystalline NiSi_2/Ti_5Si_3 Composite Coating

采用双阴极等离子溅射技术在TC4合金表面制备了纳米晶NiSi2/Ti5Si3复合涂层。利用XRD、SEM和TEM研究了复合涂层的微观组织特征,利用纳米压入和声发射划痕仪考察了复合涂层的硬度、弹性模量以及涂层与基体的结合力。结果表明:纳米晶NiSi2/Ti5Si3复合涂层由外层厚度为7μm的NiSi2沉积层和其下3μm厚的Ti5Si3扩散层组成,沉积层的平均晶粒尺寸约为40nm,而扩散层的平均晶粒尺寸约为70nm,且存在大量的栅栏状孪晶。纳米晶NiSi2/Ti5Si3复合涂层硬度呈梯度分布,与基体具有较高的结合强度,其结合力为49N。纳米晶NiSi2/Ti5Si3复合涂层的比磨损率较TC4合金降低一个数量级以上,且对载荷和温度不具敏感性。与TC4合金相比,纳米晶NiSi2/Ti5Si3复合涂层的腐蚀电流密度降低了两个数量级,且具有更大的容抗弧值。

The nano-crystalline NiSi2/Ti5Si3 composite coating was prepared on TC4 alloy substrate surface by double cathode glow discharge technology. The composition and microstructure of the nano-crystalline composite coating were analyzed by XRD, SEM and TEM. Nanoindentation and scratch test were used to assess its hardness, elastic modulus and adhesion property between the coating and the substrate. The results indicate that the nano-crystalline NiSi2/Ti5Si3 composite coating is composed of two different layers, NiSi2 deposition layer with average grain size of 40 nm, which is the outer layer of 7 mu m thickness, and Ti5Si3 diffusion layer with average grain size of 70 nm which is the inner layer of 3 mu m thickness. A large number of twins are found in the diffusion layer. The nano-crystalline NiSi2/Ti5Si3 composite coating combines closely with TC4 alloy substrate with an adhesive strength of 49 N and the hardness of the composite coating presents gradient distribution. The specific wear rate of the nano-crystalline NiSi2/Ti5Si3 composite coating is one order of magnitude lower than that of TC4 alloy, and the composite coating is very insensitive to the test load and temperature. Compared with TC4 alloy, the corrosion current density of the nanocrystalline NiSi2/Ti5Si3 composite coating is decreased by two orders of magnitude. The Nyquist plots of the nanocrystalline NiSi2/Ti5Si3 composite coating consist of single capacitance arc with a higher value.