铸造镍基合金CW12MW与CW6MC平衡凝固及析出热力学模拟

Thermodynamic Simulation of Equilibrium Solidification and Precipitation of CW12MW and CW6MC Cast Nickel-based Alloys

利用Thermo-Calc(TC)热力学计算软件以及专业的TCNI10镍基数据库,针对铸造镍基合金CW12MW与CW6MC平衡凝固与冷却过程的相变路径以及两种材质的主要合金元素,对各自平衡体系的垂直截面相图的影响分别展开计算分析。计算结果表明:铸造镍基合金CW12MW平衡凝固及冷却过程的相变路径依次为:L→L+γ→L+γ+M6C→γ+M6C→γ+M6C+σ→γ+M6C+σ+M_(23)C_(6)→γ+M6C+σ+M_(23)C_(6)+μ→γ+σ+M_(23)C_(6)+μ,其平衡转变过程中析出主要的金属间相为σ相与μ相,最大相摩尔分数分别为0.27与0.0037,Cr、Mo及W元素主要促进σ及μ相的形成与稳定;铸造镍基合金CW6MC平衡凝固及冷却过程的相变路径依次为:L→L+γ→L+γ+γ′-Ni_(3)(Al,Ti)→γ+γ′-Ni_(3)(Al,Ti)→γ+γ′-Ni_(3)(Al,Ti)+σ→γ+γ′-Ni_(3)(Al,Ti)+σ+δ-Ni_(3)Nb→γ+γ′-Ni_(3)(Al,Ti)+σ+δ-Ni_(3)Nb+M_(23)C_(6)→γ+σ+δ-Ni_(3)Nb+M_(23)C_(6)→γ+σ+δ-Ni_(3)Nb+P+M_(23)C_(6)→γ+δ-Ni_(3)Nb+P+M_(23)C_(6),其平衡转变过程中析出主要的金属间相为σ相与P相,最大相摩尔分数分别为0.17和0.25,Mo含量的增加有利于σ相的形成与稳定,Nb含量的增加主要促进δ-Ni_(3)Nb相的析出。理论计算与生产实践表明,铸造镍基合金CW12MW与CW6MC适宜的固溶温度分别为(1230±14)℃和(1200±14)℃。

Thermo-Calc(TC)thermodynamic calculation software and TCNI10 professional nickel-based alloy database were used to calculate and analyze the phase transition paths during the equilibrium solidification and cooling process of CW12MW and CW6MC cast nickel-based alloys,as well as the effects of the main alloy elements of these two alloys on the vertical section phase diagrams of equilibrium systems.The results indicate that the phase transition paths during the equilibrium solidification and cooling process of nickel-based alloy CW12MW are respectively:Liquid→Liquid+Austenite→Liquid+Austenite+M6C-carbide→Austenite+M6C-carbide→Austenite+M6C-carbide+Sigma→Austenite+M6C-carbide+Sigma+M_(23)C_(6)-carbide→Austenite+M6C-carbide+Sigma+M_(23)C_(6)-carbide+Mu_phase→Austenite+Sigma+M_(23)C_(6)-carbide+Mu_phase,the main intermetallic phases precipitated are Sigma phase and Mu phase during equilibrium transition process,and their maximum molar fractions are 0.27 and 0.0037,respectively,Cr、Mo and W elements mainly promote the formation and stability of Sigma phase and Mu_phase.The phase transition paths during equilibrium solidification and cooling process of cast nickel-based alloy CW6MC are respectively:Liquid→Liquid+Austenite→Liquid+Austenite+γ′-Ni_(3)(Al,Ti)→Austenite+γ′-Ni_(3)(Al,Ti)→Austenite+γ′-Ni_(3)(Al,Ti)+Sigma→Austenite+γ′-Ni_(3)(Al,Ti)+Sigma+δ-Ni_(3)Nb→Austenite+γ′-Ni_(3)(Al,Ti)+Sigma+δ-Ni_(3)Nb+M_(23)C_(6)-carbide→Austenite+Sigma+δ-Ni_(3)Nb+M_(23)C_(6)-carbide→Austenite+Sigma+δ-Ni_(3)Nb+M_(23)C_(6)-carbide+P_phase→Austenite+δ-Ni_(3)Nb+M_(23)C_(6)-carbide+P_phase,the main precipitated intermetallic phases are Sigma phase and P_phase during equilibrium transition process,and their maximum phase molar fractions are as high as 0.17 and 0.25,respectively.The increase of Mo content is beneficial to the formation and stability of Sigma phase,and the increase of Nb content mainly promotes the precipitation tendency ofδ-Ni_(3)Nb phase.The results of theoretical calculation and production practice show that the optimum solution temperatures of casting nickel-based alloy CW12MW and CW6MC are(1230±14)℃and(1200±14)℃,respectively.