一种抗热腐蚀铸造镍基高温合金中σ相的析出及回溶  

STUDY ON THE PRECIPITATION AND DISSOLUTION OF σ PHASE IN A HOT CORROSION RESISTANCE CAST NICKLE BASE SUPERALLOY

作　　者：侯介山[1] 郭建亭[1] 袁超[1] 周兰章[1] 

机构地区：[1]中国科学院金属研究所,沈阳110016

出　　处：《金属学报》2016年第2期168-176,共9页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目30170302和51571191资助~~

摘　　要：研究了不同热处理条件下σ相的回溶规律及其对合金持久性能的影响.研究发现,在800~900℃范围内经过最长1×104h时效后,合金中产生的σ相率先在枝晶干的M23C6碳化物附近形成,之后扩展到枝晶间;随着时效温度的升高,σ相形成速度加快,σ相形核的孕育时间缩短.激活能计算结果对比表明,σ相形成初期与Co,Cr的扩散相关,稳态阶段与Mo的扩散相关;长期时效后合金在1000~1170℃固溶时,σ相都可以回溶到基体,且固溶温度越高,σ相回溶越快.σ相的回溶动力学研究表明,σ相的回溶速度受Co的扩散过程控制.对比持久实验结果表明,合金中的σ相并不能使合金变脆;经过恢复热处理,长期时效过程中析出的σ相回溶,持久寿命提高.The experimental alloy is designed and employed in high-performance industrial gas turbines as low-pressure turbine blades, working in temperature range of 750-900℃. The alloy contains high levels of refractory elements in order to increase the high-temperature mechanical properties. However, this can make the alloy prone to the formation of σ phase during service, which could deteriorate the properties further if the fraction of σ phase exceeds the safety allowances. In this study, the formation of crphase during long-term thermal exposure, dissolution of the σ phase during rejuvenation process and their influence on stress-rupture properties of a hot-corrosion resistant nickel base superalloy have been investigated. During long-term thermal exposure at 800-900℃ for up to 1 × 10^4 h, the σ phase formation is mainly in dendrite cores with a few at interdendritic regions. As the aging temperature increases, the precipitation rate of σ phase increases and the incubation time for nucleation of σ phase decreases. From the kinetic analysis, the σ phase form firstly in the vicinity or on the M23C6 in dendrite cores with the strong segregation of W, Cr and Co. The calculated activation energies of σ formation show that the early stage is related to Co and Cr diffusions and the steady stage is related to Mo diffusion. During solid solution process at 1000-1170℃, the σ phase precipitated during long-term thermal exposure dissolves to γ matrix. As the solid solution temperature is higher, the dissolution of σ phase becomes faster. Moreover, the σ phase does not embrittle the alloy. Tire reheat treatment of the alloy leads to the dissolution of precipitated σ phase and further prolongs the stress-rupture life efficiently.

关 键 词：镍基高温合金 长期时效 沉淀 固溶 Σ相 

分 类 号：TG132.32[一般工业技术—材料科学与工程] TG146.15[金属学及工艺—合金]