镍基耐蚀合金028平衡相的析出行为

摘要

为了给冶炼成分设计、热加工工艺和热处理制度提供理论依据，利用扫描电镜(SEM)和热力学计算软件Thermo­Calc 对028合金中析出相的特征进行观察和元素含量变化对其影响进行计算分析，并给出主要元素的合理控制范围。结果表明：不同状态的028合金晶内和晶界会析出σ相，720℃时效1000 h后会析出大量针状σ相；028合金的主要平衡相为γ、M23C6、σ和α­Cr相；碳含量的增加可以显著地提高M23C6的析出量和析出温度，碳含量应控制在0.02%(质量分数)以内；随着Cr和Mo 含量的增加，σ相的析出量增多，析出温度升高，由于σ相是有害相，Cr和Mo的含量需分别控制在26.5%和3.5%以内；初始Cr和Mo含量增加，基体γ相固溶的Cr和Mo含量也增加，初始Cr和Mo含量应分别控制在26.5%~27.5%和3.0%~4.0%之间。%In order to provide theoretical guidance for smelting component design, hot working and heat treatment, precipitated phases in 028 alloy were observed by scanning electron microscopy (SEM) and the effects of element contents on them were studied by Thermo­Calc software, and the reasonable control ranges of the main elements were given. The results show thatσphase precipitates at intragranular and grain boundaries of 028 alloy in different states, a lot of spiculateσphase precipitates after aging at 720℃for 1 000 h;the main equilibrium precipitated phases of 028 alloy include γ, M23C6, σ and α­Cr phases, the increase in carbon content can significantly improve the precipitation amount and precipitation temperature of M23C6, the carbon content should be controlled within 0.02%(mass fraction);with the increase of Cr and Mo contents, the precipitation amount and precipitation temperature of σ phase increase, because theσphase is harmful phase, Cr and Mo contents should be controlled within 26.5% and 3.5%, respectively;with the initial Cr and Mo content increasing, Cr and Mo contents solid­soluted in the matrixγphase increase, and the initial Cr and Mo contents should be controlled between 26.5%-27.5%and 3.0%-4.0%, respectively.