Microstructure and bonding behavior of a new Hf-bearing interlayer alloy for single crystal nickel-base superalloy

Abstract

Single crystal nickel-base superalloys have been widely used in aero-engine blades, but a limited factor is that this kind of alloy is very sensitive to hot cracking during fusion welding due to high content of {gamma}{prime}-former such as Al, Ti. Transient liquid-phase(TLP) bonding has been developed to join the superalloys susceptible to hot cracking. It is very important to design a suitable interlayer alloy which does not contain any deleterious phases and has a melting point lower than that of the base metal. At present, the interlayer alloys which generally used for superalloys are of the Ni-Cr-Si-B system. However, addition of B and Si should be avoided because these elements are harmful impurity elements in single crystal superalloys. Hf is a potential melting point depressant in the interlayer alloys which has not been evaluated up to date. The goal of this investigation is to characterize the microstructure of a Hf-bearing interlayer alloy and determine the effect of Hf on the solidification of bonding layer during TLP processes for single crystal superalloys.