锆合金表面微弧氧化陶瓷膜制备及特性分析

采用交流微弧氧化方法在一种锆合金表面制备出保护性陶瓷膜。采用SEM、EDS、XRD分析了陶瓷膜的表面形貌、截面组织、成分和相组成,并测量了微弧氧化前后锆合金的极化曲线,以评估陶瓷膜的电化学腐蚀特性。结果表明,膜层较为致密,并与锆合金结合良好。陶瓷膜由m-ZrO2、t-ZrO2、S iO2相所组成,其中S iO2相主要分布在外层膜里。微弧氧化处理后,锆合金的腐蚀电位上升,腐蚀电流密度下降,它的抗腐蚀能力得到较大提高。     

氧化薄膜对锆-4合金表面性能的影响

为了研究氧化薄膜对Zr-4合金表面性能的影响,对样品分别进行了350℃和400℃各10 min,15 min,20 min和25 min氧化.结果发现,不同条件下氧化生成的样品表面呈现不同的颜色.小角掠射X射线衍射分析(GAXRD)表明,生成的氧化物为非化学计量的六方相氧化锆.样品在0.5 mol/L的H2SO4溶液中进行电化学试验发现,氧化后样品的耐电化学腐蚀性能有所提高.而用纳米压痕仪试验的结果表明,氧化后样品有较高的纳米硬度和较低的弹性模量,意味着氧化后样品可能有更好的耐磨性.400℃氧化样品对合金性能的提高优于350℃氧化样品.     

3种锆合金的高温氧化行为

对Zr-A和Zr-B锆合金在700-1200℃的O_2中进行了等温氧化实验,观察了合金的氧化动力学行为和基体微观结构演变,并与低Sn的Zr-4合金作了对比.结果表明,700—1200℃氧化时,3种锆合金的动力学曲线基本服从抛物线规律,Zr-B合金在700℃氧化1200 s后速率出现转折;800℃时Zr-A和Zr-B合金的氧化速率出现转折;1000℃时3种合金动力学曲线由抛物线变为近似直线;1100℃以上氧化时,动力学曲线呈抛物线规律,未出现转折.在1100℃以上氧化时,合金成分对3种合金的高温氧化性能影响甚微.依据氧化增重数据得到了3种合金在700—1200℃氧化反应的抛物线速率常数K_p的表达式.     

R60705锆合金的表面氧化改性

对锆合金R60705在480、550、650、750℃加热保温4h进行了表面氧化处理,运用硬度测试、显微组织观察、XRD分析、阳极极化曲线的测试和均匀性腐蚀试验等方法对氧化层性能进行了研究.结果表明,R60705合金氧化层表面硬度明显高于基体硬度,最高达600 HV0.05.在650、750℃处理的氧化层的主要由单斜氧化锆ZrO2构成,对基体不具保护作用.过高处理温度会降低R60705合金的腐蚀电位、降低耐腐蚀性能.在550℃以下氧化4h形成多种结构混合的ZrO2,可以紧密覆盖基体形成保护,其氧化层各项性能均优于在650、750℃处理的氧化层.     

锆—4合金氧化膜中的晶粒形貌观察

用扫描探针显微镜(SPM)研究了Zr—4合金在高压釜中经360℃高温水腐蚀后氧化膜中的显微组织和晶粒形貌。从氧化膜表面上观察到的晶粒在100nm～400nm之间，比从截面上观察到的大，说明氧化膜的晶粒在腐蚀过程中仍在不断长大。从离子轰击蚀刻后的氧化膜截面上，可以区分出由大角度晶界构成的柱状晶，以及在柱状晶中由小角度晶界构成的等轴晶。在三晶交界处，常常有明显的“凹陷”，这应是空位扩散凝聚后形成的空洞，尺度在几纳米至几十纳米间。在氧化膜的截面上，除了可观察到裂纹和空洞等缺陷外，在氧化膜／金属交界处，有时还可观察到片层状的氢化锆和显示不出晶界的非晶ZrO2。     

锆合金表面交流微弧氧化膜组织与性能的研究

采用交流微弧氧化方法，在硅酸盐溶液中于锆合金表面沉积了一层厚约28μm的氧化膜。用扫描电镜（SEM），能谱（EDS）及X射线衍射（XRD）分析了氧化膜的组织形貌、元素分布及相组成。通过测量试样在5％NaCl溶液中的点腐蚀电位，评估了氧化膜的保护性能。研究结果表明：氧化膜自内而外分为3层，即过渡层，致密层和疏松层。疏松层厚度达18μm，与致密层的界面存在明显孔洞，因此结合性较差；过渡层和基体、致密层与过渡层之间结合牢固。Si元素存在于氧化膜中，这说明电解液中的SiO3^2-参与了微弧氧化反应。氧化膜主要由M-ZrO2相和T-ZrO2相组成。锆合金表面的微弧氧化膜具有良好的耐蚀性能。     

锆合金氧化膜在真空退火过程中的氧扩散行为

针对己预腐蚀生成一定厚度氧化膜的Zr-Sn-Nb合金,研究了其在不同温度下进行真空热处理过程中的氧扩散动力学及亚稳相演变行为.结果表明,真空退火后氧化膜变薄,氧在氧化锆基体中的扩散增强,并计算了特定合金中氧的扩散系数.退火后微观化学分析表明亚稳相层厚度增加.固溶氧锆基体(Zr(O))层也明显增厚.针对该现象,讨论了对应...     

Kinetics of Hydrogen Absorption and Release in Zirconium Alloys During Steam Oxidation

The kinetics of hydrogen absorption during steam oxidation in Zr–Sn and Zr–Nb alloys in the temperature range of 1,000–1,400 °C was investigated by neutron radiography. Hydrogen uptake can be subdivided into two steps: an initial phase and a state of equilibrium. The initial phase is controlled by the kinetics of hydrogen diffusion through the growing oxide layer. In the state of equilibrium, transport kinetics does not determine the hydrogen content of the material. An equilibrium is established between the hydrogen content of the gas environment and the metal phases. The temperature dependence of hydrogen absorption is Arrhenius-like at temperatures between 1,100 and 1,300 °C.     

锆及锆合金中微量铝的测定

本文介绍在硫酸介质中,先用钽试剂-氯仿萃取分离除去锆以及钛、铁、铪等;再在pH=8.5左右,用苯萃取铝-钽试剂配合物,用稀盐酸反萃取;最后在pH=5.5—6时用铬天青S比色以测定铝的方法,确定了其测定条件。本方法准确性好,灵敏度高,测定范围为0.0025%—0.035%。     

外科植入锆及锆合金制备方法

本文介绍了一种外科植入锆及锆合金的制备方法,制备过程采用国际先进设备和先进技术,这种方法制备得到的植入锆及锆合金材料具有良好的抗蠕变性能、拉伸性能、且耐高温、无毒性、耐辐射、惯性模量小,接近自然骨,在人工关节部位具有良好的实用价值。     

An Enhanced Three-Step Oxidation Process to Improve Oxide Adhesion on Zirconium Alloys

Oxidation of zirconium-based alloys results in a thermally-grown oxide scale with excellent corrosion resistance, and good wear and friction properties, which make them interesting for tribological applications. Nevertheless, adhesion of the oxide layer to the substrate must be enhanced. A new three-step oxidation process was introduced in order to achieve an improvement. Following an initial oxidation step (1st step), a heat treatment was carried out in vacuum during which the oxide dissolves and diffuses into the metallic zirconium substrate (2nd step). These two steps resulted in an oxygen dissolution layer with increased hardness formed in-between the oxide and the substrate, which serves as a bonding layer with increased thickness. In a 3rd step a new oxide layer was obtained. The improved oxide layer adhesion was characterized by indentation tests on three different groups of oxidized samples of the newly developed alloy.     

Oxidation of Zirconium Alloys in Oxygen at High Temperatures up to 1600 °C

The oxidation kinetics of the classic pressurized water reactors (PWR) cladding alloy Zircaloy-4 has been extensively investigated over a wide temperature range. In recent years, new cladding alloys optimized for longer operation and higher burn-up are being increasingly used in Western light water reactors (LWR). These alloys were naturally optimized regarding their corrosion behavior for operational conditions. The publicly available data on high temperature oxidation of the various cladding materials are very scarce. This paper presents the results of a first test series with Zircaloy-4 as reference material, Framatome Duplex cladding, Framatome M5^® and the Russian E110 alloy. The first two are Zr–Sn, the latter two Zr–Nb alloys. All materials were investigated in isothermal and transient tests in a thermal balance under argon–oxygen atmosphere. Strong and varying differences (up to 500%) of oxidation kinetics between the alloys were found till 1000 °C, where the breakaway effect plays a role. Smaller but still significant differences (20–30%) were observed at higher temperatures. Generally, the advanced cladding alloys here studied show also a favorable behavior at high temperatures during accident scenarios.     

Hydride Formation in Zirconium Alloys

The ingress of hydrogen during corrosion in service can degrade the mechanical properties of zirconium alloy nuclear fuel cladding because of the formation of brittle hydrides. The formation of these hydrides is reviewed in light of recent synchrotron radiation experimental results and phase-field modeling computational results that provide new insight on the process.     

Hydrogen Embrittlement of Zirconium Alloys

The process of hydrogen embrittlement of zirconium alloys caused by the pressure of molecular hydrogen in voids formed near threefold junctions of grain boundaries and by volume changes due to formation of hydride phases is considered. The embrittling mechanisms are physically based on the diffusion processes near structural imperfections, the leading role among which belongs to threefold junctions of grain boundaries. These structural defects possess strong stress fields and directly adjoin grain boundaries.     

锆合金的腐蚀性能研究

在不同保护温度下采用钨极氩弧焊+高纯氩气作为保护气体的焊接方法将锆R60702板材连接起来,并利用电化学腐蚀手段和金相显微的形貌观察等方法,研究R60702在醋酸中的腐蚀行为.试验结果表明:在5 mol/L的醋酸溶液中,接头的腐蚀类型以点蚀为主.保护温度在800℃时,锆R60702的耐腐蚀性能严重降低,而保护温度在315℃和400℃时,其耐腐蚀性能与严格保护下没有很明显的降低.     

锆合金疖状腐蚀研究综述

疖状腐蚀是沸水堆中锆合金表面经常发生的1种局部腐蚀现象，它的产生直接影响包壳管的使用寿命和反应堆的安全性，为了全面认识疖状腐蚀的发生、发展及其控制因素，本文总结了国内外疖状腐蚀研究方面的一些主要成果，介绍了疖状蚀斑的形貌、形成机理以及及影响因素。在形成机制方面，目前主要有KUWAE的氢积聚模型和周邦新的形核长大模型。在疗状腐蚀的影响因素方面，认为主要有表面影响、热处理影响、合金成分影响、第二组影响、辐照影响等。最后指出了提高材料抗疗状腐蚀性能的工艺措施：提高Fe Cr含量、降低Sn含量、昼减少淬火后的退火次数和退火温度、降低锆合金制品的表面粗糙可以有效提高锆合金的抗疖状腐蚀能力，最根本的措施还是使用含铌新锆合金。