【作者】 丁红燕；

【导师】 戴振东；

【作者基本信息】 南京航空航天大学 ， 机械设计及理论， 2007， 博士

【摘要】 轻质高强合金广泛用于航空、航海等领域,在雨水和海水等腐蚀介质中,材料的摩擦磨损和疲劳行为对结构的力学性能、寿命和可靠性有很大影响。钛合金和铝合金是常用的轻质合金,其耐磨性较差,故本文同时研究了这两种合金表面改性前后的腐蚀磨损特性。首先研究了TC11和LY12微弧氧化膜的相组成、表面形貌、厚度和硬度梯度。然后以440C不锈钢为对磨球,采用球-面接触方式、300μm的振幅,分别研究了TC11和LY12及其微弧氧化膜在空气、纯水、雨水和海水中的微动腐蚀磨损行为。用动电位扫描法研究了材料腐蚀磨损前后的电化学行为,用扫描电子显微镜(SEM)观察了磨屑和磨痕形貌,用能量色散谱(EDS)测试微区元素分布,用X射线光电子谱(XPS)检测了磨痕区的元素价态,用非接触式表面形貌仪观察了磨痕的三维形貌、测定了穿过磨痕中心处的截面轮廓和磨损体积损失,研究了载荷、频率以及介质对摩擦系数和磨损量的影响。结果表明,4种材料在空气中的摩擦系数和磨损量均远远高于在3种水溶液介质中的摩擦系数和磨损量,且空气中的磨损机制以氧化磨损和粘着磨损为主,明显不同于水介质中。因此,本文以纯水作为参比介质研究铝合金和钛合金在雨水和海水中的腐蚀磨损特性及交互作用,并得到以下结论:对铝合金LY12,雨水和海水形成的润滑膜均降低了其摩擦系数,介质中Cl-对磨痕表面的侵蚀使其磨损率增加,磨损率依次为:纯水中<雨水中<海水中,腐蚀磨损为正交互作用。对钛合金TC11,2种介质中形成的润滑膜也明显降低了其摩擦系数,但腐蚀磨损特性随介质和摩擦条件的不同而异:雨水中的微动腐蚀为轻微的正交互作用,海水中则为负交互作用。进一步的实验表明,微动腐蚀过程中,海水中的这种负交互作用随着频率的增加和时间的延长而逐渐变弱;随着振幅的大幅度增加,则由微动过程中的负交互逐步过渡到毫米级滑动过程中的正交互作用,体现了频率、时间、振幅对腐蚀磨损的促进效应。LY12和TC11经微弧氧化处理后,在四种介质中的耐磨性得到不同程度的提高,尤其是LY12,其微弧氧化膜在海水中的耐磨性是原LY12的7倍,腐蚀磨损性能大大提高。本文将减摩特性系数k引入到现有腐蚀磨损模型中的磨损分量上进行修正,修正后的模型对腐蚀磨损的正、负交互作用均可以作出合理的解释,通过模型分析发现,腐蚀磨损的交互作用均随着频率、时间、振幅的上升而增强,从而使得材料的腐蚀磨损总量表现为递增的趋势。更多还原

【Abstract】 The high specific stiffness and strength alloys are widely applied in the field of aviation and navigation. In the corrosive media of rain and sea water, the behavious of friction wear and fatigue would markedly affect the mechnical properties, service life, and reliability. Titanium alloy and aluminum alloy are commonly used high specific alloys with low wear resistance. So the corrosion wear characteristics of the two alloys, both before and after surface modification, were investigated in present work simultaneously.The phase, surface image, thickness, and hardness of the film which modified by method of micro-arc oxidation (MAO) in LY12 and TC11were studied firstly. The corrosion fretting behavior of LY12, TC11 and their MAO-films were consequently investigated in air, distilled water, artificial sea water and rain water respectively by using the ball-on–flat configuration against 440C stainless steel ball with 300μm reciprocating amplitude. The potentiodynamic anodic polarization was used to study the corrosion behavior of the materials before and after the corrosion wear. The morphology and composition of the wear scars were observed and analyzed by using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). Elements valence in wear scars were also detected by X-ray photoelectron spectroscopy (XPS). 3D-morphology, profiles across the centre, and wear volume loss were determined by using a non-contact optical profilometer. The influences of load, frequency and media on the friction coefficient and wear volume of materials were analyzed.Results showed that both the friction coefficient and wear loss of the four kinds of materials in air were all much higher than those in the other three aqueous. Meanwhile, the wear characteristic in air, presented as oxidation and abrasion wear, is different from those in aqueous. So, the distilled water was selected as referrenced medium to study the corrosion-wear characteristic and their synergism between corrosion and wear. Some summaries obtained were listed as follows:As for LY12 aluminum alloy, lubrication films formed in seawater or rainwater can reduce the corresponding friction coefficient, but the specific wear rate increased due to the erosion effection of chlorin ion on the wear scar. The specific wear rate increased as following sequence: in distilled water, in rain, and in sea water, which demonstrate the positive synergism between corrosion and wear.As for TC11 titanium alloy, lubrication films formed in the two corrosive media reduced the corresponding friction coefficient, but the wear-loss presented different trends with different media and wear parameters. It was approved as slight positive synergism in rainwater and negative synergism in seawater when fretting corrosion was carried out. Further experiments showed that the negative synergism would weaken gradually as time goes by in the fretting corrosion, and it would change into positive interaction when amplitude increased from fretting scale to sliding in meter scale. It demonstrated the accelerating effection of frequency, duration, and amplitude on synergism between corrosion and wear.All the wear resistances of LY12 and TC11 in the four media were increased in different degree after MAO treatment, especially for MAO-LY12, which wear resistance in searwater was 7 times as much as that of original LY12. The corrosion-wear property was remarkably improved.The special anti-friction modulus k was introduced into current corrosion-wear model to modify the wear offset. Both positive and negative synergism can be perfectly explained by the modified model. Analyzed by the new model can be found that the synergism was enhanced as increasing of frequency, duration, and amplitude, which resulted in the increasing of the total wear-loss in corrosive medium.更多还原