【作者】 张珊珊；

【导师】 李春峰；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2010， 硕士

【摘要】 钛合金由于其密度小、比强度、比刚度高以及其他优异特性,得到了广泛应用,然而钛合金的摩擦性能较差,这与其固有性能有关。本文对置氢的TC4钛合金粉末进行了温热磁脉冲压制成形,并对压坯进行了烧结和除氢热处理。为了给粉末烧结体的应用提供理论指导,对粉末烧结体进行了滑动摩擦试验,得到了不同氢含量粉末制件的摩擦磨损性能。为了改善其耐磨性,对粉末烧结体进行了热氧化和氧化（TO）+真空扩散（OD）两种表面处理,并对这两种表面处理后的试样进行了滑动摩擦试验。研究结果表明,粉末压坯致密度随着氢含量的增加而降低,随着压实温度的增加而增加,而且不同氢含量粉末压坯之间致密度的差别降低。粉末压坯硬度随压实温度提高而增大。氢在烧结过程中对粉末制件致密度的提高起到了积极作用。烧结除氢后粉末制件硬度随压实温度的增加而提高,且不同氢含量粉末制品之间硬度的差别减小。热氧化处理在试样表面形成一层致密的不导电涂层,且随氧化时间和氧化温度的增加,氧化层逐渐增厚,但氧化层过厚会出现脱落现象。其主要产物由外侧一薄层的Al₂O₃和内侧的TiO₂组成。氧化层内侧有一个因氧扩散形成的硬化层,厚度可达到80μm⁹0μm左右。TO+OD处理试样表面的氧化物非常细小和疏松,试样表层的TiO₂分解,形成了低价态的氧化物TiO;硬化层可达到200μm左右,且预氧化时间对硬化层的厚度没有明显影响。氢含量对粉末制品滑动摩擦磨损量的影响与试样致密度规律相一致。粉末制品的磨损机制为磨粒磨损为主,伴有一定程度的粘着磨损。随氢含量的增加,试样粘着磨损程度减轻。热氧化后试样的磨损率比粉末制件基体小两个数量级。其磨损机制为氧化膜在较高载荷发生脆性断裂,氧化膜磨屑十分细小,起到抛光的作用,露出的基体在摩擦后并未产生明显的划痕。TO+OD处理试样的磨损率比粉末制品基体小两个数量级;且在预氧化时间较短时,磨损率比热氧化试样小;表面附着的细小氧化物起到减磨作用。更多还原

【Abstract】 Titanium alloys have excellent combination of attractive properties, including small density, high specific strength, high specific stiffness, etc. But it has terrible frictional behavior which is due to its proper properties. In this article, hydrogenated Ti6Al4V alloy powder was compacted by magnetic pulse compaction. Then, sintering and vacuum annealing was investigated. In order to provide theory directs for the use of vacuum annealed samples, it was investigated by sliding contact conditions. Thermal oxidation process and thermal oxidation （TO） +oxygen diffusion （OD） have been investigated to improve the wear-resistance of samples. Then the sliding frictional properties of the two kinds of surface treatments were investigated.The results show that the relative density of compacts didn’t increase by the addition of hydrogen. Compaction temperature enhances the relative density and reduces the relative density differences of compacts with different hydrogen content. Compaction temperature can increase the hardness of compacts. Hydrogen has good effects on the improvement of the relative density during sintering process. Compaction temperature improves the hardness of vacuum annealed samples and reduces the difference between different hydrogen content.The coating formed by thermal oxidation is compact and insulated, its thickness increase as the temperature and time increase, but the coating may break off when it is too thick. The main substance of the coating is Al₂O₃ which is at the surface of the coating and TiO₂ at the inside. On the inner side of the coating, there is a strengthened layer penetrated by oxygen, its thickness can be 80⁹0μm. The surface oxides of TO+OD treated samples are small and tiny and it contains TiO. The strengthened layer of this samples can be 200μm, with basically no difference between different TO treat times. The effects of hydrogen on the wear-resistance of vacuum annealed samples are as the same of relative density. The main wear mechanism of vacuum annealed samples is fatigue wear with a certain extent of abrasive wear. The extent of abrasive wear was lightened as hydrogen extent increased.The wear rate of thermal oxidation treated samples is smaller than that of vacuum annealed samples by two orders. And its wear mechanism is the brittle cracking of thermal oxidation coating. The abrasive dusts are tiny, so they have the effects of polish. The wear rate of TO+OD treated samples is also smaller than that of vacuum annealed samples by two orders. When the TO treated time is appreciated, the wear rate of TO+OD treated samples is smaller than that of thermal oxidation treats samples. The tiny oxides of its surface have the effects of reducing wear.更多还原