MICROSTRUCTURE AND PERFORMANCE OF Ni-Hf BRAZING FILLER ALLOY
ZHENG Yunrong;RUAN Zhongci Institute of Aeronautical Materials; Beijing Senior Engineer; Laboratory No.4;Institute of Aeronautical Materials; Beijing 100095
Cite this article:
ZHENG Yunrong;RUAN Zhongci Institute of Aeronautical Materials; Beijing Senior Engineer; Laboratory No.4;Institute of Aeronautical Materials; Beijing 100095. MICROSTRUCTURE AND PERFORMANCE OF Ni-Hf BRAZING FILLER ALLOY. Acta Metall Sin, 1990, 26(2): 125-131.
Abstract 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.
