Study on the Mechanism of Diffusion Brazing of Ni-Base Superalloys

Abstract

In this study, bonding mechanism of diffusion brazing of Ni-base superalloys was considered theoretically based on the experimental results. Main experimental results obtained in this research are as follows;
1) In the diffusion brazing joint using Ni-P plating film as an insert metal, a Ni-P film melted at a bonding temperature and a thin liquid film was formed at the bonding region. P in the liquid film diffused into base metal with holding at the bonding temperature and as the result, the width of the liquid film decreased with increasing holding time.
2) From the theoretical considerations on the disappearing process of the liquid film, it was clarified that this process was controlled by the diffusion process of P in the base metal.
3) The elements contained in the base metal diffused into the bonding interlayer in the homogenizing process and finally, the concentration difference of these elements between base metal and bonding interlaver vanished.
4) It is concluded that in the diffusion brazing joints of Ni-base superalloys, both isothermal solidication processes controlled by the diffusion processes of depressants and mutual diffusion processes of main .alloying elements of base metal have important roles in the diffusion brazing process.