Transient liquid phase bonding of newly developed haynes 282 superalloy

Transient Liquid Phase Bonding (TLP) of Haynes 282 was performed to study the influence of process parameters on TLP joint microstructure in the newly developed superalloy. Insufficient holding time for complete isothermal solidification of liquated insert caused formation of eutectic-type microconstituent along the joint centerline region. In contrast to general expectation, an increase in bonding temperature above a certain temperature resulted in a decrease in isothermal solidification rate and formation of the centreline eutectic that was avoided with same holding time at a lower temperature. Application of finite element numerical simulation showed that the anomalous behaviour can be explained by deviation from parabolic relationship between solid/liquid interface migration and holding time induced by reduction in solute concentration gradient in the solid substrate below a critical value. Comparison of the present experimental results in Haynes 282 with those in other nickel based superalloys, like IN 738, shows that the undesirable reduction in isothermal solidification rate is significantly less pronounced in the Haynes 282. This is attributable to a more extensive formation of interface Mo-rich borides in the new alloy, which can relieve boron saturation in the matrix phase and, thus, lessens the occurrence of the deviation phenomenon. (AU) © 2010 by The Materials, Metals, & Materials Society. All rights reserved.