高Cr镍基合金的高温内氧化和内氮化行为

通过对镍基合金进行不同温度的恒温氧化试验、横断面的组织形貌观察及微区成分分析,研究一种高Cr镍基合金在恒温氧化期间的氧化物分布特征、内氧化及内氮化行为。结果表明:该高Cr镍基合金在850、900、950和1 000℃空气中氧化100 h期间,合金表层发生元素的外氧化,且在外氧化膜中出现分层结构,由表及里各层中的主要氧化物分别为Al2O3、Cr2O3、NiCr2O4和NiAl2O4、Cr2O3、CrTaO4和Al2O3;合金在900℃以下为完全抗氧化级,900~1 000℃为抗氧化级。该合金在各温度的恒温氧化期间,均发生元素Al的内氧化和内氮化;与外氧化膜相邻的区域为元素Al的内氧化区,远离外氧化膜的基体内部形成元素Al的内氮化区;随恒温氧化温度的升高,内氧化区和内氮化区的深度增加,内氧化物和内氮化物的尺寸增大。其中,在内氧化物、内氮化物周围形成元素Al的贫化区,在贫化区内发生-′相的分解及贫乏。

Internal oxidation and internal nitridation of Ni-base alloy with high Cr contents during high temperature exposure

By mean of the microstructure observation and composition analysis of the isothermal oxidation layers,the internal oxidation and internal nitridation behavior of the nickel-base superalloy with high Cr contents were investigated.The results show that the surface layer oxidation occurs during thermal exposure of the alloy at 850,900,950 and 1 000 ℃,and the layer structure appears in the oxidation films,thereinto,the main oxides in the layers from surface to inside,in turn,are identified as Al2O3,Cr2O3,NiCr2O4 and NiAl2O4,Cr2O3,CrTaO4 and Al2O3,respectively.The oxidation behavior of the alloy under 900 ℃ is determined as the fully oxidation resistance level,the oxidation behaviors of the alloy in the ranges of 900-1 000 ℃ are determined as the oxidation resistance level.The internal oxidation of the element Al occurs during the isothermal oxidization of the alloy at different temperatures.The regions near the surface oxides of the surface oxides is identified as the internal oxidizing zone of the element Al,and the matrix region far from the layer of the surface oxides is identified as the internal nitridizing zone of the element Al.And the depths of the internal oxidization,nitridizing zone and the size of the internal oxides,nitrides increase with enhancing the temperature of the isothermal oxidization.Thereinto,the poor-zone of the element Al appears in the around region near the oxides and nitrides,and the decomposition and scarceness of the - ′ phase occur within the poor-zone of the element Al.