通过静态高压釜实验研究了 NZ2、NZ8两种含Nb 锆合金在400℃/10.3 MPa蒸汽中的腐蚀规律；透射电镜及中子衍射对两种新锆合金α-Zr 基体的显微结构进行分析；X 射线衍射法、拉曼光谱法研究了它们在400℃蒸汽中腐蚀后氧化膜的晶体结构。腐蚀规律研究表明,400℃蒸汽中,NZ2合金的耐腐蚀性能较NZ8的好。α-Zr基体的显微结构研究显示,NZ2合金第二相粒子主要包括 C14型 Zr(Fe,Cr)2和 Zr (Fe,Cr,Nb)2两种类型,α-Zr 基体中固溶的 Nb 含量低于平衡固溶度；NZ8合金中只发现了一种 Zr-Fe-Nb第二相粒子,Nb 元素过饱和存在于α-Zr 基体。氧化膜晶体结构研究显示,转折前氧化膜由四方相和单斜相组成,转折时,氧化膜内部出现了立方相,立方相的形成与Nb 的添加密切相关；氧化膜中四方相含量越高,锆合金的耐腐蚀性能越好。大量 Zr-Fe-Nb 第二相粒子以及α-Zr 基体中过饱和的 Nb 含量增加了 NZ8合金氧化膜局部体积膨胀,促进了裂纹的生成,加速了氧化膜内部四方相向单斜相的转变,从而使腐蚀加速,而α-Zr基体中低于平衡固溶度的 Nb 含量及少量 Zr (Fe,Cr)2和Zr(Fe,Cr,Nb)2第二相粒子使 NZ2合金耐腐蚀性能相对较好。
The corrosion kinetics of NZ2 and NZ8 alloys were investigated by static autoclave test in 400 ℃/10.3 MPa steam;the matrix microstructures of the two alloys were tested by TEM and neutron diffraction method.The crystal structure of oxide films of NZ2 and NZ8 alloys after corroded was investigated by XRD and Raman spectra methods in this paper.The results of corrosion kinetics indicated that the corrosion resistance of NZ2 alloy in 400 ℃/10.3 MPa steam was better than that of NZ8 alloy;TEM studies on the matrixes showed that the precipitates of NZ2 were Zr(Fe,Cr)2 and Zr(Fe,Cr,Nb)2 ,and Nb content in the matrix was less than solid solution limit.However,the precipitates of NZ8 were Zr-Fe-Nb,and Nb was supersaturated in the ma-trix.The neutron diffraction result confirmed that the Zr(Fe,Cr)2 precipitates of NZ2 matrix were C14 struc-ture.A great deal of Zr-Fe-Nb precipitates and the supersaturated Nb content in NZ8 matrix increased the local volume expansion and accelerated the crack formation,which resulted in the higher corrosion rate of NZ8.Mo-reover,the less than solid solution Nb content in the matrix and Zr(Fe,Cr)2 ,Zr(Fe,Cr,Nb)2 precipitates im-proved the corrosion resistance of NZ2 alloy.
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