Investigating the transient liquid phase bonding (TLPB) behaviour of a Palladium containing Ni-B based braze filler metal

Abstract

ABSTRACT A cyclic DSC method has been adapted to study the TLPB behaviour and isothermal solidification rate (IS) in an IN625/CPW475 base metal/filler metal joint at 1000°C. Analysis of the DSC data resulted in a prediction of the maximum brazing clearance (MBC) as a function of braze time. The rate of IS was determined to be linear with the square root of time with a rate constant k = 4.59 µm/min1/2, once the braze temperature and isothermal conditions were reached. During transient heating from the solidus temperature up to the braze temperature there is a region of rapid boron uptake by the base metal and an accelerated growth rate of the IS zone (ISZ). This initial ISZ layer, 2wISZi was predicted to be 29.5 µm. In the current case of an initial gap width of 80 µm, this initial ISZ represents 36% of the gap width.