摘要
目的在Zr-4包壳材料表面制备具有耐事故高温性能的抗氧化厚Cr涂层,保护Zr基体,以防止与高温水蒸汽反应。方法采用自主研发的φ155 mm大弧源电弧离子镀技术在Zr-4合金表面制备约20μm的Cr涂层,通过X射线衍射仪(XRD)分析氧化前后的物相变化,通过扫描电子显微镜(SEM)和电子探针(EPMA)研究厚Cr涂层在不同温度下产生的多种缺陷,探究厚Cr涂层对Zr基体的防护机制。结果当涂层沉积速率>3μm/h,制备的Cr涂层均匀致密,结合力优异,具有柱状晶结构,可经受至少15.8%的形变量,其抗塑性形变能力优异。沉积Cr层样品经过1000、1100、1200℃氧化,保温1h后快速冷却至室温,厚Cr涂层分化为Cr Ox层、Cr_2O_3层、残余Cr层和Cr-Zr扩散层。经受苛刻条件(1200℃/3600 s)测试,除保持连续性的氧化层外,在基体上仍残余良好结合的6.8μm Cr层。氧化层两次开裂阻止基体被进一步破坏。Cr-Zr扩散层是由Zr元素向Cr涂层方向渗透生长的。1200℃时,在基体近表面处产生的大尺寸隆起,是由于在近表面处韧性β-Zr(O)相转变为脆性α-Zr相,以及Cr偏聚贫Sn造成的。残余Cr层的柱状晶结构会形成Zr-O扩散通道,对涂层最后失效将起关键作用。结论 Zr合金包壳材料镀覆20μm的Cr涂层具有充分的耐事故能力,在严苛的事故条件测试下,各缺陷均未能使Zr-4合金基体暴露,涂层能够形成有效壁垒,防止锆合金基体暴露造成核事故,阻止基体进一步被破坏。
The work aims to prepare thick oxidation resistance Cr coating with high-temperature accident tolerance on Zr-4 fuel claddings(ATF),so as to protect Zr substrate from exposure to high temperature steam vapor.A 20μm Cr was prepared by a home-madeφ155 mm large arc-source on Zr-4 alloy substrate( >3μm/h).Phase composition before and after oxidation was analyzed by X-ray diffraction(XRD)and defects generated at different temperature were analyzed by scanning electron microscope(SEM)and electron probe micro-analyzer(EPMA)to investigate the protective mechanism of Cr coating to Zr substrate.When deposition rate was >3μm/h,the Cr coating was uniform and dense with excellent resultant force and columnar crystal structure and could withstand at least 15.8%of plastic deformation and had better plastic deformation ability.After coated samples were oxidized at 1000°C,1100℃,and 1200℃for 1 h and cooled in air down to room temperature(RT),the thick Cr coating turned into four sublayers to protect the Zr-4 substrate:outer CrOx layer,inner Cr2O3 layer,residual Cr layer,and Cr-Zr diffusion layer.Even after the toughest test(1200℃/3600 s),except the outer oxide layer remaining continuous adhesion to the Zr-4 alloy,a 6.8μm residual Cr layer still existed on the substrate.Twice oxide ruptures were formed to prevent the further damage.The Cr-Zr diffusion layer was formed by Zr element permeating to the Cr coating.The formation of sub-surface voids were clearly related to brittleα-Zr(O)turned byβ-Zr(O)and Sn/Cr segregations near the surface.Zr-O channels formed by columnar crystal structure of residual Cr layer were the key factors of coatings failure.The^20μm Cr coating cladded on Zr alloy has sufficient accident tolerance.Zr-4 alloy substrate is not exposed under severe accident condition for all flaws.The thick Cr coating can create effective barriers to prevent the zirconium alloy substrate from causing nuclear accident and avoid further damage to the substrate.
作者
胡小刚
董闯
陈宝清
杨红艳
张瑞谦
谷伟
陈大民
HU Xiao-gang;DONG Chuang;CHEN Bao-qing;YANG Hong-yan;ZHANG Rui-qian;GU Wei;CHEN Da-min(Key Lab of Materials Modification by Laser,Ion,and Electron Beams(Ministry of Education),Dalian University of Technology,Dalian 116024,China;Key Lab of Reactor Fuel and Materials,Nuclear Power Institute of China,Chengdu 610200,China;Dalian Nano-Crystal Technology Co.,Ltd,Dalian 116600,China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2019年第2期207-219,共13页
Surface Technology
