超级奥氏体不锈钢654SMO在900℃下的时效析出行为

Aging precipitation behavior of super austenitic stainless steel 654SMO at 900℃

对超级奥氏体不锈钢654SMO在900℃进行不同时间的时效处理,通过扫描电镜(SEM)、透射电镜(TEM)观察了析出相的显微形貌,使用能谱分析和选区电子衍射分析了析出相的成分和结构,并结合JMA方程对析出相的析出动力学进行了研究。结果表明,超级奥氏体不锈钢654SMO中的析出相主要是σ相和Cr2N相。时效10 min~1 h时,钢中析出相主要是σ相,σ相的析出位置依次是晶界、非共格孪晶界、共格孪晶界和晶内。时效1~12 h过程中,σ相开始在晶内形成针状相,随着时效时间的延长,析出相的数量越来越多,并在晶内相互交错,交织成网状。在时效24、48 h后,由于σ相富含Cr,以及σ相与奥氏体相晶界结构差异大,Cr2N相以条状或不规则的块状依附在σ相上形核生长。超级奥氏体不锈钢654SMO中析出相的析出动力学方程为X=1-exp(-0.0487t0.729)。

Super austenitic stainless steel 654SMO was aged at 900℃for different time.The microstructure of the precipitated phase was observed by scanning electron microscope(SEM)and transmission electron microscope(TEM).The composition and structure of the precipitated phase were analyzed by energy spectrum analysis and selected area electron diffraction.The precipitation kinetics was studied by JMA equation.The results show that the precipitated phases in the super austenitic stainless steel 654SMO are mainlyσphase and Cr2N phase.During the aging process from 10 min to 1 h,the precipitated phases in the steel is mainlyσphase.The precipitation position ofσphase is grain boundary,non-coherent twin boundary,coherent twin boundary,and finally within grains in the sequence.During the aging process from 2 h to 12 h,theσphase begin to form needle-like phase in the grain.With the prolongation of aging time,the amount of precipitated phases become more and more.In addition,they interlace with each other and form a network in the grain.After aging for 24 h and 48 h,becauseσphase is rich in Cr element and the grain boundary structure is very different betweenσphase and austenite phase,Cr2N phases nucleate on theσphases in strips or irregular chunks.The precipitation kinetics equation of precipitated phase in the steel 654SMO is X=1-exp(-0.0487t0.729).