铝合金钻杆材料的腐蚀性能研究

发布时间：2018-04-25 08:01

本文选题：铝合金 + 钻杆　；参考：《吉林大学》2015年硕士论文

【摘要】：铝合金钻杆具有低密度、高比强度、无磁性以及良好的耐低温性能，在石油钻探、海洋钻探、极地钻探以及大陆深部科学钻探中越来越发挥着重要作用，，有着非常广泛的应用前景。可热处理强化的高强度铝合金7075和2024是制备铝合金钻杆的典型材料。因其具有良好的力学性能，已经在大陆科学钻探和极地科学钻探等领域得到部分应用。但是，由于铝合金对含有氯离子(Cl-)的环境具有较强的腐蚀敏感性，铝合金钻杆在海洋钻探、含盐地层和含盐钻井液的环境使用过程中，不可避免地会面临由Cl-所致的腐蚀问题。因此，研究和评价7075和2024铝合金钻杆在Cl-环境下的腐蚀性能就显得尤为重要。本文亦对一种试研的、具有高强度高耐磨性的原位析出TiB2粒子的7075复合材料进行了腐蚀性能研究。采用动电位极化试验，定量研究、分析了三种材料的腐蚀敏感性和腐蚀速率；应用扫描电镜(SEM)，能谱分析(EDS)和电子背散射衍射(EBSD)技术研究铝合金材料的腐蚀机制，分析了合金成分、相组成、晶界特征分布（GBCD）和晶粒变形能等因素对腐蚀的影响。研究表明，2024铝合金钻杆的耐腐蚀性高于7075铝合金钻杆，且随着挤压比的不同，钻杆不同部位的腐蚀性能有很大差异。从腐蚀机制来看，7075铝合金钻杆的腐蚀形式包括点蚀、晶间腐蚀和剥蚀；而2024铝合金只有点蚀和晶间腐蚀两种腐蚀形式。两种材料的腐蚀性能区别主要是由于两者合金成分以及热处理方式不同造成的。 7075-TiB2铝基复合材料的腐蚀率与TiB2颗粒的比例呈现对应关系。该复合材料的腐蚀行为主要与由原位TiB2颗粒引起的位错密度的变化有关。该种铝基复合材料在腐蚀过程中主要表现出点蚀和晶间腐蚀两种腐蚀形式；而且点蚀发生于晶内。7075-TiB2铝基复合材料的选择性点蚀具有晶粒间非对称的特点，主要归因于由TiB2颗粒与铝基体的热膨胀系数错配所致的局部位错密度不同。组织中的富Cu的金属间化合物与铝基体间的界面腐蚀缘于成分不均所致的电化学反应。其脱落导致微点蚀的发生。铝合金及铝基复合材料的晶间腐蚀的选择性特点主要与晶界特征分布(GBCD)有关。大角度晶界易于腐蚀，而特殊晶界和小角度晶界具有耐腐蚀性。
[Abstract]:Aluminum alloy drill pipes with low density, high specific strength, nonmagnetic properties and good low temperature resistance are playing more and more important roles in oil drilling, offshore drilling, polar drilling and deep continental scientific drilling. It has a very wide application prospect. High strength aluminum alloy 7075 and 2024, which can be strengthened by heat treatment, are typical materials for producing aluminum alloy drill pipe. Because of its good mechanical properties, it has been used in some fields such as continental scientific drilling and polar scientific drilling. However, because aluminum alloy has a strong corrosion sensitivity to the environment containing chloride ion, aluminum alloy drill pipe will inevitably face the corrosion problem caused by Cl-in the process of offshore drilling, salt formation and environment use of salt drilling fluid. Therefore, it is very important to study and evaluate the corrosion resistance of 7075 and 2024 aluminum alloy drill pipes under Cl- environment. The corrosion properties of a kind of in-situ precipitated TiB2 particles with high strength and high wear resistance were also investigated in this paper. The corrosion susceptibility and corrosion rate of three kinds of materials were analyzed by potentiodynamic polarization test and quantitative study, and the corrosion mechanism of aluminum alloy was studied by means of SEM, EDS and EBSD. The effects of alloy composition, phase composition, grain boundary characteristic distribution (GBCD) and grain deformation energy on corrosion were analyzed. The results show that the corrosion resistance of 7075 aluminum alloy drill pipe is higher than that of 7075 aluminum alloy drill pipe, and the corrosion resistance of different parts of drill pipe varies greatly with different extrusion ratio. From the corrosion mechanism, the corrosion forms of aluminum alloy drill pipe include pitting corrosion, intergranular corrosion and denudation, while 2024 aluminum alloy has only two corrosion forms: pitting corrosion and intergranular corrosion. The difference of corrosion performance between the two materials is mainly due to the difference of alloy composition and heat treatment. The corrosion rate of 7075-TiB2 aluminum matrix composites is proportional to the proportion of TiB2 particles. The corrosion behavior of the composite is mainly related to the change of dislocation density caused by in situ TiB2 particles. In the process of corrosion, the aluminum matrix composites mainly show pitting corrosion and intergranular corrosion, and the selective pitting corrosion of aluminum matrix composite occurs in the intragranular. 7075-TiB2 aluminum matrix composite has the characteristics of asymmetric grain size. The local dislocation density due to the mismatch of thermal expansion coefficient between TiB2 particles and aluminum matrix is mainly attributed to the difference of local dislocation density. The interfacial corrosion between Cu-rich intermetallic compounds and aluminum matrix is due to the electrochemical reaction caused by uneven composition. Its shedding results in the occurrence of micropitting. The selective characteristics of intergranular corrosion of aluminum alloy and aluminum matrix composites are mainly related to the distribution of grain boundary characteristics (GBCDs). Large angle grain boundary is easy to corrode, and special grain boundary and small angle grain boundary have corrosion resistance.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P634.4

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