参照含Hf铸造镍基合金在凝固最后阶段包围γ枝晶的富Hf熔体,熔炼了Ni-18.6Co-4.5Cr-4.7W-25.6Hf合金钎焊料。这种共晶合金初生的Ni_5Hf相呈长棒状,γ+Ni_5Hf共晶中的γ相为领先相,棒状γ相被Ni_5Hf相包围。在垂直和平行于γ生长方向的磨面上共晶分别呈蜂窝状和片状。合金中Ni_5Hf相含量为68.7v.-％。初生和共晶中的Ni_5Hf相成分相近,主要为Ni,Co,Hf。而Cr和W在该相中的溶解度很低。该合金是一种较理想的定向和单晶高温合金用的钎焊料。其组成元素都是有益元素。熔点低,流动性好,在10~(-3)Pa真空下经1240℃,5min+1190℃,1h钎焊处理后,焊缝区的显微组织与含Hf高温合金的完全相同,达到了无Si,B钎接。
In consideration of the envelopment of γ dendrites by the Hf-richmelts, saying brazing by the melts together, at the late period of solidification of thecast Ni-base superalloys containing Hf, a heat of brazing filler alloy composed ofNi-18.6Co-4.5Cr-4.7W-25.6Hf (wt-%) was prepared. This alloy is hypereutectic. γphase is the leading phase in eutectic γ+Ni_5Hf and γ bars are surrounded by Ni_5Hfphase. At the section perpendicular or parallel to the γ growing direction, the eutec-tic morphology is cellular or laminar respectively. The content of Ni_5Hf in thealloy is 68.7 v. -%. The compositions of primary and eutectic Ni_5Hf are very similar.Ni, Co and Hf are the main elements and the solubility of Cr and W in Ni_5Hf isvery low. This alloy is an ideal brazing filler suitable to the directional or singlecrystal superalloys, and the elements are beneficial to superalloys at all. This alloyis of low melting point and of good fluidity. After brazing at 1240℃, 5 min+1190℃, 1h under 10~(-3) Pa vacuum, the microstructure of bond is as same as thatof Hf-bearing superalloy. No more Si and B will be contaminated.
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