Microstructure Evolution During Transient Liquid Phase Bonding of Alloy 617

Abstract

Transient liquid phase bonding was used to join Alloy 617 alloy using nickel-based filler metal (Ni-P 11 wt%) with P as the melting point depressant element. The influences of interlayer thickness, 25.4 and 38.1 μm, bonding temperature, 1,065 and 1,150 °C, and hold time, 5 min to 24 h, on microstructure evolution in the joint area, the diffusion zone and the base metal were investigated. Specifically, the composition, type, and crystallography of precipitates were determined and their evolution was related to process variables. Joints were characterized using optical and electron microscopy as well as microhardness testing. The results were analyzed in the framework of the diffusion, classical nucleation and growth theory, and the operating mechanisms identified. Based on the results of the investigation, uniform microhardness and microstructure across the joints was obtained with the 25.4-μm-thick interlayer bonded at 1,150 °C during 24 h. © 2013 Springer Science+Business Media New York and ASM International.