Solid solution strengthening of transient liquid phase bonded nickel based superalloy

Abstract

This paper aims at probing and quantifying the effect of filler alloy chemistry on solid solution strengthening mechanism of transient liquid phase bonded of a cast Ni–Fe–Nb based superalloy. Bonding was performed using three different nickel based filler alloys including Ni–4·5Si–3·2B, Ni–7Cr–4·5Si–3·2B–3Fe and Ni–15·2Cr–4B. The hardness of isothermal solidification zone was proved to be the controlling factor for the shear strength of the joints. It is concluded that the initial chromium content of the filler alloy and the extent of base metal dissolution, which in turn is controlled by the initial boron content of the filler alloy, play important roles in strengthening of the isothermal solidification zone. Bonding using Ni–15·2Cr–4B resulted in eutectic free joint with the highest shear strength.

Keywords:

• TLP bonding
• Superalloy
• Strengthening
• Isothermal solidification
• Filler alloy

Acknowledgement

The author gratefully acknowledges the support from Professor H. N. Han during his sabbatical leave in the Department of Materials Science & Engineering, Seoul National University.