Brazing of Cr2AlC and 316H stainless steel using BNi-2 filler: Microstructure, properties and joining mechanism

Abstract

Cr2AlC, a ternary carbide, has been successfully brazed with 316H stainless steel using the BNi-2 filler, thereby expanding their potential applications. The diffusion of Ni from the filler into both Cr2AlC and 316H dominates the formation of the joint microstructure. High temperature leads to the detachment of Al from the Cr2AlC matrix, retaining the porous Cr7C3 along the diffusion interface. Along with the inward diffusion of Ni from the filler, the NiAl phase will be formed within the porous Cr7C3, collectively constituting the reaction layer. However, these void defects cannot be completely filled, leaving micro-voids along the Cr2AlC interface. It weakens the performance of the brazed joints. Elevated temperature and longer holding time will lead to a thicker reaction layer along the matrix interface, consequently decreasing the joint strength. A maximum joint shear strength of 248 MPa is achieved at 1000 °C/1 min. Inhibiting the excessive detachment of Al can be an efficient way to reduce the thickness of the reaction layer and increase joint performance.