氢化锆表面Cr-C-O氢渗透阻挡层XPS分析

在空间堆中,氢化锆作为慢化剂的工作温度为650～750℃,在此温度范围内,H/Zr原子数之比大于1.8的氢化锆中的氢很容易析出.通过X射线光电子能谱(XPS)研究了电镀法制备的氢化锆表面氢渗透阻挡层的化学态,对镀层进行了深度(100、200、300nm)刻蚀分析和镀层原子的定量分析.结果表明,镀层中含有C、O、Cr和Zr,进行氢渗透试验后(700℃保温)的试样镀层的C-H键数量有明显增加,而O-H键的数量变化不大.由此可以说明,氢渗透受阻的原因是氢在渗透过程中被镀层中的C优先捕获生成C-H键.     

氢渗透阻挡层在CO2中的破坏

为了了解氢渗透阻挡层在700℃下的CO2气氛中的工作能力,用电镀Cr-C的方法在氢化锆表面建立氢渗透阻挡层后,在0.1MPa的CO2气氛中700℃下保温72h,再用SEM对其表面进行观察分析.结果发现,阻挡层有粉化现象且在局部发生脱皮和剥落.分析粉化的原因是阻挡层中的碳达到过饱和,在脱落处的表面发现的空洞可以说明预存的物理缺陷是阻挡层发生剥落的必要条件.由此可以确定这种氢渗透阻挡层在700℃下不宜在CO2气氛中使用.     

Al-Cr涂层低温扩散制备及其相组成的研究

通过水溶液镀Cr后再用AlCl₃-EMIC (氯化1-甲基3-乙基咪唑)离子液体镀Al, 制备Cr/Al复合镀层, 其后通过低温扩散热处理制备Al-Cr涂层. 用OM, SEM, BSE, EDS和XRD研究了短时间热处理时, 热处理温度对Al-Cr涂层组成和结构的影响. 结果表明, Cr/Al复合镀层在540 ℃时即可发生明显的互扩散, 形成Al-Cr合金层. 通过对复合镀层中Cr和Al镀层厚度的控制, 可以得到不同组成的Al-Cr合金涂层. 6.5 μm Cr/15 μm Al的复合镀层经640 ℃/960 min热处理, 表面形成以Al₈Cr₅为主的合金涂层; 1.6 μm Cr/15 μm Al的复合镀层经 600 ℃/30 min热处理, 可得到以Al₄Cr为主的Al-Cr涂层.     

不同Al2O3粒径复合镀层的耐磨性能

用化学镀的方法制备了不同粒径的镍-钨-磷/Al2O3复合镀层,研究了热处理温度对镀层硬度和磨损性能的影响,并将含有50 nm、500 nm、1～3 μm Al2O3粒径的复合镀层的性能进行对比.结果表明:含有50 nm Al2O3粒径的复合镀层具有更高的硬度和耐磨性,经400 ℃处理后的镀层耐磨性最好.     

非晶态Cr-C合金镀层的晶化规律

采用电沉积方法制备了非晶态Cr-C合金镀层,对镀层进行热处理并测试硬度,用DSC和XRD表征镀层晶化过程,结果表明,镀层在300℃开始晶化,450℃左右晶化结束,600℃左右有Cr7C3、Cr23C6化合物析出。由于Cr的微晶化和Cr7C3、Cr23C6化合物的析出,600℃以下时,镀层硬度随温度的升高而升高,600℃时达到最高值1610 HV0.025。600℃以上时,因晶粒粗化镀层硬度迅速下降。     

热处理温度对Ni-W-P镀层耐蚀性能的影响

采用失重法及电化学方法对镀态和热处理后的Ni-W-P镀层在5%硫酸溶液中的耐蚀性能进行了研究.比较了不同温度热处理后Ni-P镀层和Ni-W-P镀层的耐蚀性能,并结合X射线衍射(XRD)、扫描电镜(SEM)对镀层的耐蚀性机理进行了分析.结果表明,Ni-P镀层在400～700℃热处理后耐蚀性能下降,而Ni-W-P镀层的耐蚀...     

热处理对电沉积纳米晶铬镀层微观结构及耐蚀性的影响

目的改善H13钢表面纳米晶Cr镀层的微观结构和耐腐蚀性能。方法利用电沉积技术在H13钢表面制备纳米晶Cr镀层,并通过调整热处理工艺调控Cr镀层的结构和性能。通过扫描电子显微镜(SEM)、原子力显微镜(AFM)和X射线衍射仪(XRD)、维氏显微硬度计和中性盐雾试验(NSS)研究了不同热处理工艺下Cr镀层的表面形貌、粗糙度、相结构、硬度及耐蚀性。结果采用电沉积技术成功在H13钢表面制备出体心立方结构的纳米晶铬镀层,其晶粒和微裂纹尺寸随着热处理温度(200～600℃)和保温时间(1～2h)的增加而增大。当热处理温度达到400℃时,镀层表面检测到Cr2O3氧化层,并随着热处理温度和保温时间的增加,氧化程度逐渐增大。此外,Cr镀层硬度随着热处理温度和保温时间的增加而逐渐降低。在600℃下保温2h后,镀层硬度为(499.8±9.3)HV0.2,与镀态((749.0±13.2)HV0.2)相比,大约下降了33%。然而,经500℃和600℃热处理的镀层具有最好的耐蚀性能,盐雾试验后,镀层表面未见明显腐蚀缺陷,保护评级为10级。结论随着热处理温度和保温时间的增加,镀层晶粒变大,表面氧化程度加剧,耐蚀性能显著增强。     

去氢工艺对20Cr2Ni4钢冲击韧度的影响

研究了热处理及去氢工艺对20Cr2Ni4钢冲击韧度的影响.结果表明,含有氢的20Cr2Ni4钢经淬回火后再进行去氢处理后其冲击韧度急剧下降;然而,若先对20Cr2Ni4钢进行去氢处理,再重新淬回火后钢的冲击性能却又显著提高,这说明去氢工艺对含有氢的20Cr2Ni4钢的冲击性能有十分显著的影响.去氢处理工艺对冲击性能的影响可能与氢在钢中的存在方式有关.去氢后,由氢析出后留下的空位或空洞造成缺陷处应力集中加剧了钢的脆化;而去氢后又重新热处理,钢中既无氢又不存在因氢析出而留下的空位或孔洞,因此导致20Cr2Ni4钢冲击韧度明显提高.     

镍基高温合金表面Al2O3活性扩散阻挡层的研究

采用EB-PVD在DD5镍基高温合金与Ni Cr Al涂层之间沉积Zr O2作为先驱层,并对试样分别进行600℃/4 h,700℃/4 h及900℃/4 h真空扩散处理,研究了扩散温度对α-Al2O3活性扩散阻挡层形成的影响,并且通过900℃/100 h恒温氧化处理对活性扩散阻挡层的高温服役性能进行了评价。结果表明:经过900℃/4 h真空扩散处理后,在Zr O2/Ni Cr Al界面形成一层连续致密的α-Al2O3扩散阻挡层,并且经过900℃/100 h大气恒温氧化后,α-Al2O3活性扩散阻挡层表现出良好的稳定性,以及优异的阻扩散能力。     

水溶液中电沉积C0-La薄膜及其性能研究

在氨基乙酸为络合剂的水溶液中采用恒电位法沉积出Co-La薄膜,分别研究了pH、沉积电位对镀层结构的影响.结果表明,在镀液pH=4.5时随沉积电位负移,镀层中La含量先增后减;当沉积电位为-1.050 V(vs. SCE),镀液pH值从4.05至4.90变化时,镀层中La含量增大.循环伏安实验证实:Co-La沉积属诱导共沉积.采用XRD研究了镀层的晶化行为,结果表明:镀态镀层含有Co(hcp)相和非晶相,700℃热处理后晶化为Co-La(fcc)固溶体和Co13La合金相.电化学实验表明,Co-La电极比纯Co电极具有更好的析氢电催化活性.Co-La薄膜具有优异的硬磁性能.     

Properties of hydrogen permeation barrier on the surface of zirconium hydride

A hydrogen permeation barrier was manufactured by the in situ reaction of zirconium hydride with oxygen.A reduction in the hydrogen permeation of the oxide films was detected by measuring the mass difference of the zirconium hydride samples after the dehydrogenation experiment.The reaction of zirconium hydride with oxygen occurs only under the condition that the temperature is higher than 673 K in the oxygen partial pressure of 0.1 MPa.The oxide film is composed of two layers,a permeable oxide layer and a dense oxide layer,and the main phase of the oxide film is ZrO2 with baddeleyite structure.The XPS analysis shows that O-H bonds exist in the oxide film,which are helpful for resisting hydrogen diffusion through the oxide film.     

电镀钯对锆合金吸氢性能的影响

锆具有良好的吸氢性能,被认为是储氘领域的候选材料。但由于其吸氢温度较高且吸氢动力学较慢,目前尚不能进行广泛应用。采用电镀钯的方法对锆进行表面改性,以提高其吸氢性能。结果表明：在经过镀钯且退火处理后的锆合金,在室温下可以实现吸氢,并且有适当的孕育期;与此同时,随着温度的升高,镀钯且退火处理后的锆合金孕育期缩短,吸氢速率变快。通过对微观结构进行分析,发现在氢化后,钯层与锆基板之间形成了过渡区,过渡区中存在PdH_1.33和H_0.62Zr_0.38。由此可见,过渡区中的氢化物对改善锆的吸氢性能起着重要作用。通过对动力学机制进行研究,确定在室温下,镀钯且退火处理后的锆合金吸氢过程符合一维扩散机制;而在250 ℃时,符合二维扩散机制。     

氢化锆在450~600 ℃下氧化动力学的研究

通过恒温氧化实验研究氢化锆在O2中,450～600℃温度范围内的氧化行为,分析温度和时间对氧化膜生长速度的影响规律。结果表明,氢化锆在O2中450～600℃温度范围内,表面形成氧化膜厚度的平方(D2)与时间(t)的关系曲线呈良好的线性关系,氧化反应动力学符合Wagner理论模型中的抛物线生长规律。氧原子在氧化膜中的扩散过程为氧化反应的控速步骤。扩散系数与温度遵循Arrhenius定律,扩散激活能为18724.5J/mol,据此判断氧原子在氧化膜中的扩散机制以晶界扩散占主导。     

Prevention of hydrogen degradation in titanium by deposition of TiN thin film

This paper describes the effects of using a TiN film as a possible protection layer for titanium in an aggressive chemical environment. The TiN film as a barrier of hydrogen permeation into the material was evaluated by electrochemical cathodic charging of the specimens in solutions with different pH values and temperatures. Results revealed that the thickness of hydride on the surface of the uncoated titanium increased with the increase of charging time. Higher charging temperature and lower pH value promoted the formation of hydride phases. For titanium coated with a TiN film, it effectively retarded the permeation of hydrogen into the titanium substrate. However, this was at the sacrifice of the TiN film itself.     

I-SCC Behavior Evaluation of N36 Zirconium Alloy Cladding Using Ring Tensile Test

在102,103,104Pa碘蒸气压力和350℃温度条件下对N36锆合金包壳管进行I-SCC(碘致应力腐蚀)环向拉伸试验。对拉断后的环形试样进行宏观观察。碘环境下的试样表现出脆性断口,不同于无碘环境下的杯-杯形韧性断口形貌。分析试验载荷-位移曲线及力学参数,评价试样的I-SCC敏感性。碘环境下力学性能均较无碘环境下降,且下降程度随着碘浓度的升高而增大。通过对I-SCC评价参数的筛选,采用以拉伸载荷-位移曲线下面积表示的韧性作为I-SCC敏感性评价参数,结果表明包壳管韧性随着碘浓度的增加而降低。     

Ab initio study on plane defects in zirconium–hydrogen solid solution and zirconium hydride

Hydrogen embrittlement of zirconium alloys is one of the main causes of the mechanical degradation of the fuel cladding in light water reactors, and has therefore been extensively studied. Although various conjectures have been proposed as the origin of such embrittlement, it is not known which one plays the most important role: the brittle nature of the hydride, micro-crack nucleation by interaction of hydride precipitates with dislocations or void nucleation at the interface between hydride precipitates and zirconium matrix. The purpose of the present study was to elucidate the origin of the embrittlement by investigating the fracture properties of the hydride. We have evaluated the surface energy γ_S and unstable stacking energy γ_US of Zr–H systems by using ab initio calculations. The ductile/brittle behavior of the hydride is discussed based on the difference between γ_S and γ_US among the hydride, pure zirconium and hydrogen solid solution. For the solid solution at a H/Zr ratio less than 0.5 we obtained a monotonous decrease by 15–34% and 50–100% in γ_S and γ_US, respectively, from those in pure zirconium, indicating a reduction in both brittleness and ductility. Thus, hydrogen-induced embrittlement of the hcp Zr matrix was not confirmed. On the other hand, for the hydride we obtained a 25% smaller γ_S and a 200–300% larger γ_US than those in pure zirconium. This indicates that zirconium hydride has an extremely brittle nature due to the synergistic effect of a small γ_S, implying easy generation of a fracture surface, and large γ_US, implying a difficulty in dislocation motion, compared with pure zirconium. Furthermore, Rice’s ductile/brittle parameter D was 1.4 in the δ-hydride, indicating that it undergoes brittle fracture more easily than iridium, known as an extremely brittle material. These results seem sufficient to attribute hydrogen embrittlement of zirconium alloys substantially to the brittle nature of the hydride.     

Al2O3/Au Composite Coating on Stainless Steel Prepared by Electro-deposition

Tritium permeation barriers on stainless steels are required in fusion technology in order to reduce the tritium permeation rate through the structural material into the cooling water system.Preparation of tritium permeation barrier Al2O3 is an important way to solve the problem of leakage of tritium permeation.It is worth to note that the noble Au is an excellent barrier of hydrogen dissolution.Al2O3/Au composite coating was designed for potential tritium permeation barrier on stainless steel.The alternation coatings have been prepared by electrochemical deposition method.The processing parameters and subsequent sinter temperature for composite coatings were optimized.The oxidation resistance of the coating has been tested.A hydrogen diffusion test simulating tritium permeation has been conducted to compare the sample with and without coating.Microstructure was examined by scanning electron microcopy(SEM).The results showed Al2O3/Au multi-alternation coatings can be prepared on the surface of stainless steel at the case of controlling processing well.The coatings have the characteristic of high temperature oxidation resistance and good hydrogen permeability barrier.The tritium permeation should be study further.     

SiC/Ni基合金激光熔覆层磨损性的研究

采用扫描电子显微镜、盘销式摩擦磨损试验机等方法对45钢表面SiC／Ni基合金激光熔覆层的组织和磨损性进行了试验分析。结果表明,激光熔覆后试样从表面至心部可分为熔覆区、结合区、热影响区和基体。熔覆层显微组织以枝状晶和胞状晶为主,结合层以细晶为主,激光熔覆层与基体结合良好。磨损试验结果显示激光熔覆可显著改善钢的耐磨性,SiC／Ni基合金复合熔覆层比Ni基合金熔覆层具有更好的耐磨性;在一定成分范围内,适当提高熔覆层中SiC的含量,可提高材料的耐磨损性能。     

Hydrogen evolution and corrosion behavior of zirconium tubing in sub- and supercritical water

Hydrogen evolution is inevitable during the oxidation of zirconium in high-temperature water. A fraction of this evolved hydrogen diffuses into the cladding material, and the remaining is carried away by the reactor coolant. In this study, hydrogen evolution and corrosion behavior of zirconium-702 in high-temperature water are investigated using a continuous tubular flow-through reactor. The results show that at a constant pressure of 25 MPa, the evolution of hydrogen gas from an oxidized zirconium reactor surface is approximately 24 times larger at 500°C than at 350°C. At higher temperatures, the zirconium reactor tubing exposed to water shows ballooning, with bending before the rupture near the exit end of the reactor tube, where the concentration of evolved hydrogen is the highest.     

锆合金表面Cr涂层在高温压缩下的界面开裂行为EI北大核心CSCD

在事故条件下核反应堆的核心部件镀Cr锆合金包壳管容易受到挤压发生变形,导致Cr涂层产生裂纹影响涂层的保护性能,因此研究镀Cr锆合金在高温压缩下的裂纹扩展行为十分有必要。采用环向压缩试验研究不同厚度Cr涂层锆合金在不同温度下的开裂行为,通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)和维氏硬度计等测试设备研究不同压缩试验温度下的镀Cr锆合金包壳管表截面裂纹微观形貌,并统计表截面裂纹密度及截面裂纹最大宽度。分析包壳材料的载荷-位移曲线和裂纹扩展行为,评价温度和涂层厚度对镀Cr锆合金包壳管力学性能的影响。研究结果表明:镀Cr锆合金包壳管在高温工况下,抗压强度会下降,断裂韧性增加;当涂层厚度增加时,表截面裂纹密度减少,裂纹张开尺寸增大;裂纹首先在表面产生,然后逐渐向基体扩展,并随着变形量的增加逐渐向基体扩展,最终在膜基结合处停止;试样变形量从10%压缩到50%时,截面裂纹的新增主要来自表面主裂纹分叉,且在压缩过程中Cr涂层并不会剥落,Cr涂层与锆基体结合性能良好。研究不同厚度锆合金Cr涂层包壳管在高温压缩下的膜基界面裂纹的扩展行为,可为锆合金包壳管的涂层制备提供数据支持。