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本文采用两种定向凝固工艺即功率下降(P.D)法和快速凝固(H.R.S)法研究了不同Hf含量对一种镍基高温合金组织和性能的影响。实验结果表明,加入合金中的Hf主要偏析在枝晶间和γ/γ′共晶相内;合金加Hf后,显微组织发生明显变化:γ/γ′共晶相大量增多,其形态也发生明显变化;晶界和枝品间状态得到改善;出现了几种新的富Hf微量相。合金760℃持久性能(特别是横向性能)随Hf含量的增加显著提高。但1040℃的持久寿命却随Hf含量的增加而下降。采用H.R.S工艺时合金的中、高温性能均明显优于P.D法工艺。 文中讨论了合金加Hf后组织和性能变化的机理,确定了本合金较合适的含Hf量为1.0～2.0％(重量),并认为应优先采用H.R.S定向工艺。
In this paper, the effect of different Hf content on the microstructure and properties of a nickel-base superalloy was studied by two kinds of directional solidification process (P.D. and H.R.S). The experimental results show that the main segregation of Hf in the alloy is in the interdendritic and γ / γ ’eutectic phases. The microstructure of the alloy is obviously changed after Hf addition: the γ / γ’ eutectic phase increases greatly, A significant change occurred; the grain boundary and the interdependency improved; several new Hf microfacies appeared. The long-term properties (especially the transverse properties) of 760 ℃ alloy with Hf content increased significantly. However, the life expectancy at 1040 ℃ decreased with the increase of Hf content. The H.R.S process alloy at mid and high temperature performance were significantly better than P.D process. In this paper, the mechanism of the microstructure and properties of the alloy after Hf addition is discussed. It is confirmed that the Hf content of this alloy is 1.0-2.0% by weight, and the H.R.S oriented process should be prioritized.