【作者】 林修洲；

【导师】 朱旻昊；

【作者基本信息】 西南交通大学 ， 材料学， 2010， 博士

【摘要】 扭动微动是在法向载荷下接触副发生的往复微幅相对扭动。扭动微动现象在工业各领域普遍存在,且常运行于特定的腐蚀性介质中。作为4种基本微动运行模式之一的扭动微动,至今研究甚少,已有的研究也都集中在干态,关于液体介质中的扭动微动腐蚀的研究尚未见报道。因此,本研究具有探索未知的科学意义,不仅丰富和发展了微动摩擦学的基本理论,而且对于认识人工关节的损伤失效机理,也有一定的价值。论文基于高精度低速往复回转台,外加恒温循环水系统和电化学分析系统,成功研制了恒温扭动腐蚀磨损试验装置,真实模拟了恒温液体介质中的扭动微动腐蚀过程,试验结果有很好的可比性和重现性。论文选用人工关节常用材料Ti6A14V合金与ZrO2陶瓷配副,在多种环境(干态、纯水、Saline溶液和Hank’s溶液)下系统地进行了的扭动微动磨损和扭动微动腐蚀试验研究。在动力学特性和腐蚀电化学行为分析的基础上,结合表面轮廓仪、光学显微镜(OM)、激光共焦扫描显微镜(LCSM)、扫描电子显微镜(SEM)、电子能谱(EDX)、X射线光电子能谱(XPS)和原子吸收光谱等微观分析手段,系统地研究了钛合金的扭动微动磨损和扭动微动腐蚀的运行与损伤行为,并对磨损与腐蚀的交互作用进行了定性和定量分析。获得的主要结论如下：(一)钛合金在模拟体液中的电化学腐蚀行为钛合金在两种模拟体液(Saline和Hank’s溶液)中都存在较明显的钝化现象,腐蚀速度很低；带缝隙试样的腐蚀速度略高于自由表面试样,但并未出现明显的缝隙腐蚀或孔蚀。缝隙的存在阻碍了试样表面钝态的形成,降低钝态稳定性,从而略微加速钛合金的腐蚀。相同条件下,钛合金在Hank’s溶液中的腐蚀电位略高于Saline溶液,腐蚀速度略低。(二)钛合金扭动微动磨损运行和损伤机理研究建立了空气和纯水两种环境下,钛合金的扭动微动运行工况图。在纯水中,三个运行区域的摩擦扭矩时变曲线显示出不同的规律。由于纯水对钛合金几乎没有腐蚀作用,两种环境下钛合金的扭动微动磨损机理相似,但由于纯水的润滑与排屑作用,二者也存在一些差别：(a)部分滑移区：接触中心黏着无损伤,微滑和损伤发生在接触边缘的圆环内,磨痕呈环状,磨痕宽度不随循环次数变化；损伤机制主要表现为接触边缘的轻微磨粒磨损和擦伤。(b)混合区：随着循环周次的增加,中心黏着区逐渐缩小,损伤区逐渐向心部扩展,直至完全覆盖整个接触区；磨痕轮廓呈“W”型,干态下磨屑排出困难,存在一定的磨屑层堆积现象。混合区的损伤机理主要是磨粒磨损、氧化磨损和剥层,并伴有轻微的材料转移。(c)滑移区：钛合金试样发生较严重的磨损,磨痕呈“U”型轮廓,纯水下轮廓深度更大；两种环境下损伤区都存在较明显材料转移现象,该区的损伤机制主要表现为严重的磨粒磨损、剥层和氧化磨损。(三)钛合金扭动微动腐蚀运行和损伤机理在两种模拟体液中,钛合金的腐蚀电化学行为与扭动角位移幅值密切相关。当角位移幅值增大到一定程度时,扭动开始后,腐蚀电位负移,腐蚀电流增大；相同载荷下,对Hank’s溶液中的钛合金腐蚀电位产生影响所需的最小扭动角位移幅值低于Saline溶液。扭动对钛合金电化学腐蚀的阴极反应影响不大,而对钛合金阳极反应产生显著影响,扭动磨损造成钛合金表面钝化膜破坏,使磨损区露出的新鲜金属成为腐蚀活性点,并导致钛合金试样表面较严重的缝隙腐蚀。研究建立了两种模拟体液中钛合金的扭动微动腐蚀运行工况图。与Saline溶液相比,钛合金在Hank’s溶液中的混合区向滑移区扩展,宽度大于Saline液。三个运行区域的摩擦扭矩曲线显示出不同的演变规律。法向载荷、角位移幅值、循环周次对钛合金的扭动微动腐蚀行为有显著影响。两种模拟体液中的材料损失体积都随角位移幅值和法向载荷增大而增大；在相同试验工况下,Hank’s溶液中的损伤体积均大于Saline溶液。在不同微动运行区域,钛合金的扭动微动腐蚀损伤机理存在较大的差异：(a)部分滑移区：损伤轻微,主要以磨损为主,腐蚀不明显；磨痕呈环状,损伤机制同干态和纯水。(b)混合区：随循环周次的增加,中心黏着区逐渐缩小,损伤区域逐渐向心部扩展,磨痕轮廓主要呈“W”型,存在较明显的腐蚀痕迹。损伤机理主要是磨粒磨损、氧化磨损和剥层,其中在Hank’s溶液中还伴有一定的材料转移和电化学腐蚀。(c)滑移区：整个接触区自始至终均处于完全滑移状态,发生较严重的损伤,磨痕轮廓呈“U”型,在接触区表面覆盖较厚的磨屑层,并伴有较明显的材料转移现象。损伤机制主要表现为磨粒磨损、氧化磨损和剥层,并伴有较严重的材料转移和电化学腐蚀。(四)钛合金扭动微动腐蚀过程中磨损与腐蚀的交互作用大量定量分析的结果显示：扭动对腐蚀的加速作用与扭动角位移幅值、法向载荷及介质种类密切相关。在较小角位移幅值下,扭动对腐蚀几乎不产生影响；在较大角位移幅值下,扭动对腐蚀的加速作用显著,且随角位移幅值增大,扭动加速腐蚀增量增大。在相同角位移幅值下,载荷越大,扭动对腐蚀的加速作用增强。在相同工况下,Hank’s溶液中扭动加速腐蚀的作用强于Saline溶液。腐蚀对磨损的加速作用受载荷控制。在低载荷下,两种模拟体液的腐蚀作用都不会加速钛合金扭动磨损,反而有减缓作用,磨损增量为负；而在高载荷下,获得相反的结果。在模拟体液中,钛合金扭动微动腐蚀过程材料损伤以磨损为主,交互作用总量与腐蚀加速磨损增量具有相似的规律。在低载荷下出现较明显的负交互作用,且Hank’s溶液中的负交互作用强于Saline溶液；在高载荷下出现较明显的正交互作用,且Saline溶液的正交互作用强于Hank’s溶液。更多还原

【Abstract】 Torsional fretting can be defined as a relative angular motion which is induced by reciprocating torsion in an oscillatory vibratory environment. It often occurs in varied industrial fields, and frequently runs in corrosive media. As one of the four basic motion modes of fretting, the torsional fretting has been rarely studied up to now. The existing researches on torsional fretting were carried out mostly in the dry environment, and the researches on torsional fretting corrosion in fluid media have not been reported yet. Therefore, this research has scientific significance to explore unknown, and will not only enrich and develop the basic theory of fretting tribology, but also has some practical values for understanding the failure mechanism of the artificial joints.In this paper, a new-style device for torsional corrosion wear test rig in liquid media at constant temperature was successfully developed on a low speed reciprocating rotary system with a constant temperature circulating water system and an electrochemical analysis system. The test device can actually simulate torsional fretting corrosion process in the liquid media at constant temperature, and its test results presented better comparability and repeatability.In this paper, Ti6A14V titanium alloy and ZrCO2 ceramic, which are commonly used as artificial joint materials, were selected as the counter-pair. The studies on torsional fretting wear and torsional fretting corrosion in varied environments (dry, pure water, Saline solution and Hank’s solution) were carried out systemically. The running and damage behaviors of the torsional fretting wear and torsional fretting corrosion were investigated systematically, based on the analyses of torsional dynamics and electrochemical corrosion behaviors and combined with many micro-analytical means such as surface profile-meter, optical microscope (OM), laser confocal scanning microscopy (LCSM), scanning electron microscopy (SEM), electron energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy and so on. The qualitative and quantitative analyses for the interaction of wear and corrosion during the torsional fretting corrosion were conducted. The conclusions obtained in this thesis are as follows:(1) Electrochemical corrosion behaviors of titanium alloy in simulated body fluidThe obvious passive phenomenon of titanium alloy presented in simulated body fluids (Saline and Hank’s solutions), and their corrosion rates were very low. The corrosion rates of the samples with crevice were slightly higher than that of the samples without crevice, but no significant crevice corrosion or pitting corrosion appeared on all samples. The existence of the crevice impeded the formation of passive state of the samples to reduce the passive stability. Thus, the corrosion rate of titanium alloy slightly accelerated. Under the same conditions, the corrosion potential of titanium alloy in Hank’s solution was slightly higher than that of in the Saline solution, and the corrosion rate was slightly lower than that of in the Saline solution.(2) Running and damage mechanisms of titanium alloy during torsional fretting wear processThe running condition fretting maps (RCFMs) of torsional fretting for titanium alloy in two environments of air and pure water were established, respectively. The friction torque time-varying evolution curves presented different principles in the three running regimes. As pure water was almost no corrosiveness on titanium alloy, the torsional fretting wear mechanisms of titanium alloy in the both environments were very similar, but some differences existed because of the lubrication and debris removal action in pure water.(a) In the partial slip regime (PSR):No damage was observed in the contact center due to the sticking. The micro-slip and slight wear occurred in the ring area of the contact boundary. So, the wear scar appeared in shape of annularity and the width of scar unchanged with the increase of the number of cycles. In the PSR, the damage mechanisms of torsional fretting for titanium alloy in air and pure water mainly were slight abrasive wear and scuffing at the contact edge zone.(b) The mixed fretting regime (MFR):With the increase of the number of cycles, the sticking zone in the contact center gradually reduced, and the damage zone spread to the contact center until all the contact zone was covered. The profile of the wear scar presented the type of "W". Under dry conditions, the wear debris was difficult to remove from the wear scar, and the debris layer covered on the wear scar surface. In the MFR, the damage mechanisms for titanium alloy in air and pure water mainly were abrasive wear, oxidation wear and delamination, and companied with some slight materials transfer.(c) In the slip regime (SR):The much severer wear and the typical "U"-type profile of wear scar appeared on titanium alloy samples. The depth of wear scar in pure water was greater than that of in air. Obvious material transfer occurred on damage areas of test samples in the both environments. In the SR, damage mechanisms of titanium alloy mainly were severe abrasive wear, delamination and oxidation wear.(3) Running and damage mechanisms of torsional fretting corrosion for titanium alloyElectrochemical corrosion behaviors of titanium alloy during the torsional fretting corrosion in the both simulated body fluids were closely related to the torsional angular displacement amplitudes. When the angular displacement amplitude increased to a certain degree, the corrosion potential shifted negatively and the corrosion current increased at the beginning of torsional motion. The requisite minimum torsional angular displacement amplitude for the corrosion potential negatively shifting in the Hank’s solution was lower than that of in the Saline solution. The torsional fretting had a little effect on the cathodic reaction but a significant impact on the anode reaction in the electrochemical corrosion of titanium alloy. The passive film on surface of titanium alloy samples damaged due to the torsional fretting wear, and the exposed fresh metal surface on the worn zone became the active sites of corrosion, which induced serious crevice corrosion on the titanium alloy sample surface.The running condition fretting maps (RCFMs) of torsional fretting corrosion for titanium alloy in the both simulated body fluids were established, respectively. To compare with the Saline solution, the MFR of titanium alloy in Hank’s solution enlarged to the PSR, and its width was greater than that of in the Saline solution. The friction torque curves in the three running regimes showed different evolutions.The normal load, angular displacement amplitude and number of cycles had a significant effect on torsional fretting corrosion damage behaviors of titanium alloy. In the both simulated body fluids, the damage volumes increased with the increase of the angular displacement amplitudes and normal loads. Under the same test conditions, the damage volumes in Hank’s solution were higher than that of in the Saline solution. In the different torsional fretting running regimes, there were some differences on torsional fretting corrosion damage mechanisms of titanium alloy:(a) In the partial slip regime (PSR):The damages were main wear that was slight, and the corrosion was hardly observed. The wear scars appeared in shape of annularity and the damage mechanisms were similar to that in dry environment and pure water.(b) In the mixed fretting regime (MFR):With the increase of the cycles, the center sticking zones gradually shrank, and the damage zones extended to the contact center. The profile of the wear scar presented the type of "W", and some obvious traces of corrosion were observed. In the MFR, the damage mechanisms of titanium alloy in the both simulated body fluids mainly were abrasive wear, oxidation wear and delamination, and companied with slight material transfer and electrochemical corrosion in the Hank’s solution,(c) In the slip regime (SR):The gross slip state presented on entire contact zones all time, and much severer wear occurred. The typical "U"-type profile of wear scar appeared, and a thick layer of debris covered the contact surface. In the SR, the damage mechanisms of titanium alloy of torsional fretting corrosion mainly were abrasive wear, oxidation wear and delamination, accompanied with severer material transfer and electrochemical corrosion.(4) Interaction between wear and corrosion of torsional fretting corrosion of titanium alloyA large number of quantitative analysis results indicated that the accelerated effect of torsional fretting on corrosion was closely related to the angular displacement amplitudes, normal loads and the medium types. When the angular displacement amplitudes were lower, the torsional fretting had almost no effect on the corrosion. Under the larger angular displacement amplitudes, the torsional fretting significantly accelerated the corrosion, and the corrosion increment induced by the torsional fretting increased with the increase of the angular displacement amplitudes and normal loads. Under the same test conditions, the accelerated effect of torsional fretting on corrosion in the Hank’s solution was greater than that of in the Saline solution.The accelerated effect of corrosion on torsional fretting was controlled by the normal load. When the normal load was lower, the corrosive effect of the simulated body fluids did not speed up the wear of titanium alloy, inversely slowed it down, and the increment of wear volume was negative. However, under the higher normal loads, a reverse result can be obtained.In the simulated body fluids, the damage of titanium alloy of the torsional fretting corrosion mainly was wear, and there was a similar law between the interaction volume and the wear volume increment. Under the lower normal loads, the significant negative interaction occurred, and the negative interaction in the Hank’s solution was stronger than that of in the Saline solution. Under the high normal loads, much obvious positive interaction appeared, and the interaction in the Saline solution was stronger than that of in the Hank’s solution.更多还原