【作者】 张晓宇；

【导师】 周仲荣；

【作者基本信息】 西南交通大学 ， 机械设计及理论， 2013， 博士

【摘要】 能源已成为严重制约我国经济与社会持续发展的战略问题,而安全、高效地利用核能则是解决能源问题的重要途径。核电系统中,蒸汽发生器是关键设备之一由于蒸汽发生器一回路和二回路热传导及高温高压介质流致振动,使传热管与支撑部件之间产生微动磨损,导致传热管局部损伤甚至破裂,使用寿命降低,危及核电安全。因此,防止蒸汽发生器传热管的破损,提高核电设备安全性和使用寿命,是核电工程的重大课题。开展不同环境法向交变载荷下微动磨损的试验研究,不仅对探索特殊工况下的复杂微动损伤机理具有重要意义,而且也能为核电设备抗微动损伤设计及运行安全提供理论支持和工程实践指导。基于高精度液压式微动磨损试验机,通过附加径向电磁激振加载装置和控制系统,成功研制了高温可控气氛传热管微动磨损试验装置,实现了试验模拟高温、可控气氛及法向交变载荷下的微动磨损过程,试验数据具有良好的重现性和稳定性。本文选用两种传热管(Inconel690和Incoloy800合金),在不同环境(常温大气、高温大气、高温氮气、纯水和碱性去离子水溶液)下,系统地进行了微动磨损试验。在微动运行行为分析的基础上,结合光学显微镜(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)、X射线衍射(XRD)和原位纳米力学测试系统等微观分析手段,系统揭示了传热管切向微动磨损的运行行为和损伤机理。获得的主要结论如下：1.高温(300℃)、可控气氛及法向交变载荷下Incone1690合金的微动运行特性及损伤机理(1)针对Incone1690合金,系统研究了在不同环境法向交变载荷下微动的运行特性。结果显示,微动运行行为与径向频率密切相关,微动的Ft-D曲线呈现摩擦力周期波动的平行四边形型特征,微动运行于滑移区。(2)在不同环境条件下,摩擦力的动态变化均可以分为5个阶段,即跑合阶段、上升阶段、峰值、下降阶段和稳定阶段。环境温度和含氧量对摩擦力产生显著影响。常温大气环境下的稳态摩擦力比300℃大气环境下高,比300℃氮气环境低。(3)Incone1690合金在不同环境法向交变载荷下的微动损伤行为强烈地依赖于载荷、位移幅值、环境温度、气氛及径向频率等试验条件。从表面损伤形貌看,径向频率和气氛对磨屑的形态、化学成分及结构有重要影响；由于交变法向力和切向力的共同作用,微动产生叠加效应,使剥层现象更加突出。在常温大气环境下,Incone1690合金的磨损机制主要表现为磨粒磨损与剥层。在300℃大气环境下,Incone1690合金的磨损机制主要表现为磨粒磨损、氧化磨损与剥层。而在300℃氮气环境下,Incone1690合金的磨损机制主要是磨粒磨损与剥层。2.水及碱性去离子水中Incone1690合金的微动运行特性及损伤机理(1)在滑移区,水及碱性去离子水均具有润滑作用,降低摩擦系数。水中的摩擦系数比碱性去离子水低；摩擦系数随介质温度增加而增加。(2)Incone1690合金在碱性去离子水中,磨损程度除受到位移幅值、载荷影响以外,温度对磨损体积有显著影响。温度增加,虽然促进了联氨与溶解氧的吸收反应,起到了降低氧化腐蚀的作用,但因金属氧化物的致密性和稳定性下降,材料磨损更加严重。Incone1690合金在水中磨损机制主要表现为磨粒磨损、氧化磨损和剥层,而在碱性去离子水中磨损机制主要是磨粒磨损和剥层。3.大气环境中Incoloy800合金的微动运行特性及损伤机理(1)载荷、位移幅值、温度及材料性质等对微动的运行区域和损伤行为有重要影响,温度的变化未对微动运行区域特性产生显著影响。(2)在部分滑移区,磨痕呈现环状,接触中心黏着,微滑、轻微的磨损和微裂纹发生在接触边缘的椭圆环内;磨损机制主要表现为轻微的磨粒磨损和微裂纹。(3)在混合区,在常温大气下,接触中心因强烈的塑性变形,产生颗粒状的磨屑；随温度升高,摩擦氧化效应增强,易聚集的氧化磨屑覆盖于接触区；温度升高到400℃,磨痕表面呈现高温氧化和塑性流变特征；磨损机制主要是磨粒磨损、氧化磨损与剥层。(4)在滑移区,在常温大气下,材料表面以剥层方式剥离,损伤较为严重；而在高温大气下磨痕表面呈现出清晰的层状结构和塑性流动特征；在此区域磨损机制主要表现为氧化磨损、磨粒磨损与剥层。更多还原

【Abstract】 Energy problem has been limiting the sustainable development of domestic economy and society, as a strategically severe problem, the solution of which lies in safe and efficient use of nuclear energy. Steam generator (SG) tube is an important component in nuclear power plants. SG (Steam Generator) is one of the major equipment of nuclear power systems, and heat exchanger tube is a key component of SG. Inside the SG of nuclear power plants, the flow-induced vibrations usually cause an oscillatory movement with the relatively small amplitude between heat exchanger tubes and their supports, where fretting wear might occur due to the combined effect of stress and media. The phenomena would lead to a reduction of U-tubes life time. Therefore, it is of great importance to prevent the damages of the heat exchanger tubes in order to enhance the safety and service life of the nuclear power equipment. Thus the research on the tangential fretting under alternating loads is not only of significance to realize and understand the mechanisms of the fretting damages, but also can provide theoretical supports and practical guides for engineering application of nuclear power equipment in the resistance against fretting.On the basis of hydraulic fretting test system, a new-style device for the fretting wear test rig, by employing the radial cyclic loading device and control system, has been developed, which can actually simulate the fretting wear process under alternating loads in high temperature and controlled atmosphere environment. The tester presents high stability, and its test results indicate a better comparability and repeatability.The fretting tests have been carried out by the new-style device. The systematic studies have been conducted on the fretting wear behavior of two typical heat exchanger tubes (Inconel690and Incoloy800) in different environments (air, high-temperature air, high-temperature nitrogen, water, and alkaline ionized water). The fretting running behaviors and damage mechanisms of the fretting have been studied systematically, based on the frictional dynamic behavior analyses and by means of the optical microscopy (OM), laser confocal scanning microscopy (LCSM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and triboindenter in-situnanomechanical test system. The main research work and obtained conclusions are listed as follows:1. The running and damage mechanisms of the fretting for Inconel690under alternating lo-ads conditions in high temperature (300℃) and controlled atmosphere environment(1) The running behaviors of the fretting of Inconel690alloy have been investigated in detail. The research revealed that the fretting running behaviors were closely related to the radial frequency. In parallelogram shaped Ft-D curves, the friction fluctuates periodically, and accordingly, the fretting was running in the slip regime (SR).(2) Five stages of friction force curves could be observed in different environments, i.e. initial stage, ascending stage, peak value, descending stage and steady stage. Under the same conditions, the oxygen content of the atmosphere and temperature had significant effect on the friction force. The steady-state friction force in air at room temperature was higher than that at300℃, while much lower than that in nitrogen at300℃.(3) The damage behaviors of the fretting for Inconel690strongly depended on the normal load, displacement amplitude, temperature, atmosphere and radial frequency in different environments. By observing the damage morphology, the radial frequency and atmosphere had a major impact on the morphology, chemical composition and structure of the wear debris. The delamination phenomenon became severer due to the superposition effect of the fretting under alternating loads. Specifically, compared with the single mode of the tangential or radial fretting, more severe material failure would be induced under the combination of the two modes. There were significant differences in the fretting damage mechanisms for Inconel690in different environments:The abrasive wear and delamination were the major mechanisms of Inconel690in air at room temperature. The wear mechanisms were mainly abrasive wear, oxidation wear, and delamination in air at300℃while in nitrogen at300℃, the abrasive wear and delamination were the main mechanisms.2. The running and damage mechanisms of fretting wear for Inconel690in water and alkal-ine ionized waters(1) In gross regime, the friction coefficient was reduced because of the lubricating effect of water and alkaline ionized water. It was also found that friction coefficient depended on the medium property and test parameters. The friction coefficient was lower in water than that in alkaline ionized water, while the friction coefficient increased with the increase of solution temperature.(2) The fretting wear behavior of Inconel690in alkaline ionized water was affected by the displacement amplitude, normal load and especially the temperature. The increasing temperature promoted the absorption reaction of hydrazine and dissolved oxygen, and obviously reduced oxidative corrosion rate, but the compactness and stability of the oxide films were weakened. Consequently, fretting wear became more serious. The abrasive, oxidative wear and delamination were the main mechanisms of Inconel690in water. In alkaline ionized water, whereas abrasive wear and delamination were the dominant mechanisms.3. The running and damage mechanisms of fretting wear for Incoloy800in air (1) The fretting running regimes and damage behaviors of fretting were strongly dependent upon the normal load, displacement amplitude, temperature and material properties. It was found that temperature had no significant effect on the fretting running regime.(2) In the partial slip regime (PSR), the wear scar appeared in shape of the annularity, and little damage was observed in the contact center due to the sticking. The micro-slip, slight wear and microcracks occurred in the oval ring at the contact boundary zone. The damage mechanisms were mainly slight abrasive wear and microcracks.(3) The mixed fretting regime (MFR), the debris of the crushed metallic detached particles at the contact zone were formed due to intense plastic deformation, and the debris congregated at the contact zone at room temperature. As the increase of test temperature, a large number of debris layers, produced during the fretting wear processes, could easily congregate and adhere at the contact zone. The plastic flow characteristics accompanied by adhesion traces and high temperature oxidation could be observed in wear scars at400℃. In the MFR, the damage mechanisms were mainly abrasive wear, oxidation wear and delamination.(4) In the slip regime (SR), the particles were detached by delamination mechanism at room temperature, causing severe damages. However, some phenomena of the layered structure and plastic flow characteristics could be observed on the wear surface at high temperature. The damage mechanisms were mainly abrasive wear, oxidation wear and delamination in the SR.更多还原