Hf对一种镍基高硼铸造高温合金凝固行为及疏松情况的影响

Effect of Hf on Solidification Behavior and Porosity in a Nickel-Based High-Boron Cast Superalloy

摘要:

研究了Hf的添加对一种镍基高硼铸造高温合金显微组织、凝固行为、疏松情况的影响。显微组织分析、差热分析(DSC)、等温凝固淬火试验结果显示,Hf在合金的凝固过程中强烈偏析于枝晶间区域,并在凝固末期以Ni5Hf相的形式从残余液相中析出；Hf的加入降低了合金的液/固相线温度、γ/γ′共晶相和硼化物析出温度,延缓了合金的凝固过程,加宽了凝固温度范围,显著增大了γ/γ′共晶相的含量。自主设计并浇铸一种薄壁管铸件,渗透检验结果显示Hf的加入使得薄壁管的疏松明显减少,合金的疏松倾向性显著降低。

Abstract:

The effects of Hf addition on the microstructure, solidification behavior and porosity of a nickel-based high-boron cast superalloy were studied. The results of microstructure analysis, differential thermal analysis (DSC) and isothermal solidification quenching test showed that Hf segregated in interdendritic regions during the solidification process of the alloy, and precipitated from the residual liquid phase in the form of Ni5Hf phase at the end of the solidification process. The addition of Hf reduced the precipitation temperature of liquid/solidus , γ/γ′ eutectic phase and boride, delayed the solidification process of the alloy, widened the solidification temperature range from 166.3 ℃ to 200.5 ℃, and significantly increased the content of γ/γ′ eutectic phases. A thin-walled tube cast was independently designed by ourselves. Penetration test results showed that the addition of Hf significantly reduced the porosity of the thin-walled tube, and the tendency of porosity forming of the alloy was significantly reduced.