γ’形成元素Ta和Ti含量对镍基高温合金铸态组织的影响

Effect of Contents of γ'-forming Elements Ta and Ti on Casting Structure of Nickel-based Superalloy

保持镍基高温合金中γ’相形成元素(Ta+Ti)总量3.12at%不变,采用光学显微镜、扫描电镜、电子探针、示差扫描量热测试和J MatPro软件对不同Ta/(Ta+Ti)合金的铸态组织进行了研究,分析了一次枝晶间距(λ_(1))、二次枝晶间距(λ_(2))、γ’相平均尺寸和体积分数及元素的偏析行为,探究了合金的固相线温度(TS)、液相线温度(TL)、γ’相固溶温度(Tγ’)及硬度的变化规律。结果表明,γ’相形貌随着Ta/(Ta+Ti)的提高由球形向立方状转变,λ_(1)、λ_(2)、γ’相平均尺寸及体积分数先增大后减小,枝晶间和枝晶干的γ’相尺寸差值减小。随着Ta/(Ta+Ti)的提高,W元素的偏析得到减轻,枝晶干和枝晶间的硬度及平均硬度增加。合金的凝固温度区间随着Ta/(Ta+Ti)的提高而减小,γ’相固溶温度随着Ta/(Ta+Ti)的提高而增大,使得γ’相的稳定性得到增强。

Keeping the total amount(3.12at%) of γ' phase forming elements(Ta+Ti) in the nickel-based superalloy unchanged,the as-cast structure of different Ta/(Ta+Ti) alloys were studied by using optical microscope,scanning electron microscope,electron probe micro-analyzer,differential scanning calorimetry,and J MatPro software.The primary dendrites arm spacing(λ_1),the secondary dendrites arm spacing(λ_2),the average size and volume fraction of γ' phase and the segregation behavior of elements were analyzed,and the changes of solidus temperature(TS),liquidus temperature(TL),γ' solution temperature(Tγ') and hardness of the alloys were investigated.The results show that the morphologies of the γ' phase changes from spherical to cubic with the increase of Ta/(Ta+Ti).The λ_1,λ_(2) and the average size and volume fraction of γ' phase are increased first and then decreased.The difference in the size of the γ' phase between the interdendrites and dendrites is decreased.With the increase of Ta/(Ta +Ti),the segregation of W element is reduced,and the hardness and average hardness between interdendrites and dendrites are increased.The solidification temperature range of the alloys decreases with the increase of Ta/(Ta +Ti),and the solid solution temperature of the γ' phase increases,leading to the enhancement of the stability of γ' phase.