Ti6Al4V合金干滑动磨损过程中摩擦层及摩擦氧化物的作用

目的分析Ti6Al4V合金在不同滑动速度下的干滑动磨损行为及磨损特征,研究钛合金的磨损机理,并探讨干滑动磨损过程中摩擦层及摩擦氧化物的作用。方法采用销盘式摩擦磨损试验机,对Ti6Al4V合金在不同滑动速度下进行干滑动磨损实验。采用磨损率和摩擦系数表征钛合金的磨损行为,采用SEM、EDS及XRD分析磨损表面及摩擦层的形貌及成分,采用数字显微硬度仪表征摩擦层的力学性能。结果滑动速度在0.5～4 m/s范围内变化,Ti6Al4V合金的磨损率发生显著变化,尤其是在高载条件下。0.5～1.5 m/s速度范围内,磨损率较低,2.68m/s速度下,磨损率达到最高值,4m/s速度下,磨损率达到最低值。0.75m/s速度下,粘着磨损和磨粒磨损为主要磨损机理,氧化磨损为次要磨损机理;2.68 m/s和4 m/s速度下的磨损机理分别为剥层磨损和氧化轻微磨损。2.68m/s速度下的高磨损率与硬度较低的无氧化物摩擦层对应,而4 m/s速度下的低磨损率与高硬度的多氧化物摩擦层对应。结论试验条件改变,Ti6Al4V合金的磨损行为及磨损机理发生变化。不同试验条件下的磨损行为与不同的摩擦层特征相对应,当摩擦层中包含一定量的摩擦氧化物时,这种陶瓷性的摩擦层具有比基体更高的硬度,能有效保护基体,降低磨损率。

Role of Tribo-layers and Tribo-oxides in Dry Sliding Wear Process of Ti6Al4V Alloy

The work aims to analyze the dry sliding wear behavior and wear characteristics of Ti6Al4V alloy at different sliding speed and study the wear mechanisms of titanium alloy and the role of tribo-layers and tribo-oxides in dry sliding wear process. Dry sliding wear tests of Ti6Al4V alloy at different sliding speed were preformed on a pin-on-disk wear tester. The wear behavior of titanium alloy was characterized by wear rate and friction coefficient. The morphology and composition of worn surfaces and tribo-layers were analyzed by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy, and the mechanical properties of tribo-layers were characterized by digital microhardness tester. As sliding speed varied in the range of 0.5~4 m/s, the wear rates of Ti6Al4V alloy varied obviously, especially at high loads. The wear rates were lower at 0.5 m/s to 1.5 m/s, but reached the highest at 2.68 m/s, and the lowest at 4 m/s. At 0.75 m/s, adhesion and abrasive wear were the primary mechanisms, while oxidation wear was the secondary mechanism. The wear mechanisms at 2.68 m/s and 4 m/s were delamination and oxidative mild wear, respectively. Tribo-layers with no oxides and low hardness corresponded to the maximal wear rate at 2.68 m/s, while tribo-layers with more oxides and high hardness corresponded to the minimal wear rate at 4 m/s. The wear behavior and wear mechanism of Ti6Al4V alloy vary with the test conditions. The distinct characteristics of tribo-layers are found to correspond to the wear behavior in various conditions. When tribo-layer contains some quantity of tribo-oxides, such ceramic tribo-layer has higher hardness than the matrix, thus effectively protecting the matrix and reducing the wear rate.