The bonding temperature effect of the diffusion brazing Inconel 625 superalloy on the microstructure changes, corrosion resistance, and mechanical properties

Abstract

The aim of this survey was an evaluation of the diffusion brazing (DB) bonding properties of the Inconel 625 superalloy using a BNi-3 interlayer. During the inter-diffusion and the dissolution of the alloy elements at the bonding temperature, and also cooling-cycle process, the joining zone (JZ) divided into three section namely isothermal solidification zone (ISZ), diffusion affected zone (DAZ), and athermal solidification zone (ASZ) which included a Ni-rich solid solution phase, Mo and Cr-rich boride precipitation, and Mo-rich boride precipitation and also Ni-Si binary phase, respectively. The cyclic potential-dynamic polarization tests indicated an inverse relationship between the corrosion behavior and the width of the ASZ. Also, the bonding process leads to the loss of resistance to pitting corrosion. The completion of the ISZ, together with the highest corrosion resistance attained at the bonding temperature at 1180 ᵒC. Likewise, with increasing bonding temperature, the eutectic compounds decreased and ISZ completed. The highest hardness belonged to the JZ/DAZ boundary at 1060 ᵒC and ASZ at 1120 ᵒC measured as 422 HV and 390 HV, respectively; which decreased by increasing bonding temperature, but the ISZ hardness increased.