热氧化工业纯钛表面硬化层的结构与性能

【作者】 严伟；

【导师】 王小祥；

【作者基本信息】 浙江大学 ， 材料学， 2004， 硕士

【摘要】 本文以提高医用钛合金植入体的耐磨性能和牙科用钛合金与烤瓷材料的结合性能为背景，对纯钛进行了大气热氧化处理，并对获得的氧化膜和渗氧层的微观组织结构、硬度性能和动力学生长规律进行了测试分析。 对纯钛进行退火去应力处理和去脂预处理，然后在大气环境箱式电阻炉中进行600～900℃／0.5～24h热氧化处理，得到研究试样，并对部分试样进行金相处理，制备了横截面研究试样。 采用X射线衍射法对热氧化处理后的纯钛表面进行微观组织结构测试分析。在纯钛表面生成了由金红石型二氧化钛构成的氧化膜，当氧化温度较低、时间较短时，氧化膜与金属基体结合良好，随着氧化温度的升高、时间的延长，结合力降低。氧化膜与纯金属钛之间是一层由α相Ti—O固溶体构成的渗氧层，随着氧化温度的升高、时间的延长，渗氧层含氧量增加、厚度增大。 通过光学显微镜、扫描电子显微镜对试样横截面进行了微观组织观察分析。渗氧层被一条穿越晶界而连续的界线分为内渗氧层和外渗氧层。随着氧化温度的升高、时间的延长，内、外渗氧层的厚度都增大，并且内渗氧层的厚度始终略大于外渗氧层。 对热氧比后的试样进行了表面和横截面显微硬度测试分析。随着氧化温度的升高、时间的延长，试样的表面硬度增大；随着加载载荷的增大即离表面距离的增大，硬度降低。相比较横截面显微硬度测试法，表面显微硬度测试法能测出更薄的硬化层，因此是一种更适合薄硬化层硬度表征的方法。 通过测试厚度变化表征了纯钛氧化膜和渗氧层的动力学生长规律。在氧化的前期，渗氧层和氧化膜的生长都遵循抛物线规律，随着氧化时间的延长，氧化膜的生长向直线规律转化，渗氧层的生长向直线规律转化不明显。当氧化时间较短时，渗氧层的生长速度大于氧化膜的生长速度，随着氧化时间的延长，氧化膜的生长速度超过并大于渗氧层的生长速度。温度对于渗氧层厚度的影响大于时间的影响。更多还原

【Abstract】 In an effort to improve the wear-resistance of titanium alloys for orthopaedic implants and understand the bonding behavior between dental titanium alloys and porcelain, thermal oxidation of pure titanium was systematically investigated. The microstructure, microhardness property and growth kinetics of the achieved oxide film and oxygen diffusion layer on the titanium surface were analyzed in the present research.After annealing and pretreatment, the thermal oxidation was carried out on pure titanium at 600-900for 0.5-24h in an air atmosphere. Specimens for surface analyses and cross-sectional analyses were prepared, respectively.The surface microstructure of the treated titanium was analyzed by X-ray diffraction method. The surface oxide films on all the specimens were identified to be rutile TiO2. When treated at low temperature and in short time, the oxide film bonds well with the metal substrate. While with increasing oxidation temperature and time, the adherence becomes poorer. The sublayer beneath the oxide film is an oxygen diffusion layer consisting of a -phase Ti-0 solid solution. With increasing oxidationtemperature and time, the oxygen content and thickness of oxygen diffusion layer increase.The microstructure of the diffusion layer was observed using a LEICA MPS60 optical microscope and a HITACHI S-4700 field emission scanning electron microscope (FESEM). The diffusion layer is comprised of an inner and an outer oxygen diffusion layers which are separated by a line that runs across the grain boundaries. With increasing oxidation temperature and time, the thicknesses of inner and outer diffusion layers are both increase, and the inner diffusion layer is always a little thicker than the outer diffusion layer.The surface and the cross-sectional hardnesses were measured using an HV-1000 Vickers microhardness tester. With increasing oxidation temperature and time, thesurface hardness increases. With increasing indenter load, i.e. increasing the distance from the surface, the hardness decreases. Comparing with the cross-sectional microhardness analysis, the surface microhardness analysis can detect more thinner hardening layer, so is a more sensitive method to identify the presence of surface hardening layers.The growth kinetics of oxide film and oxygen diffusion layer were characterized by measuring their thicknesses. The growth of the oxide film agrees with parabolic-linear law, and the oxygen diffusion layer agrees with parabolic law with a linear trend at the end of the growth curve. When oxidized in relatively short time, the oxygen diffusion layer thickens faster than the oxide film does. While with increasing oxidation time, the oxide film grows faster than the oxygen diffusion layer. Oxidation temperature has a more obvious effect on the thickening of oxygen diffusion layer than time dose.更多还原