中文摘要：

N18合金经轧制变形及780℃／5h热处理，在500℃／10．3MPa过热蒸汽中发生了疖状腐蚀。采用TEM和SEM研究了合金及腐蚀生成氧化膜的显微组织。结果表明，发生疖状腐蚀的原因是试样在（a＋8）两相区的热处理过程中，合金元素铌、铁、铬等大量迁移至a-Zr晶界处，形成Zr（NbFeCr）z和pZr相，造成a-Zr晶粒内部合金元素严重贫化。对于这类合金，应注意其热加工过程，尽量避免进人（a＋B）相区并保温时间过长，以防止疖状腐蚀的发生。

英文摘要：

Nodular corrosion was found in N18 zirconium alloy processed by rolling deformation and 780℃/5 h heat treatment in the superheated steam of 500 ℃/10. 3 MPa. The microstructure of N18 zirconium alloy and the oxidation films were observed by SEM and TEM. The results show that the heat treatment carried out in the （α＋β） intercritical temperature range promoted the movement of alloying elements such as Nb, Fe and Cr to the boundaries of a-Zr grains and the formation of Zr（NhFeCr）2 and β-Zr phases, thus led to the severe depletion of alloying elements in α-Zr grains and resulted in nodular corrosion in the heat treated N18 zirconium alloy. It is suggested that the heat treatment of N18 alloy should avoid to be performed in the （α＋β） intercritieal temperature range for long time so as to prevent nodular corrosion.