Shear Strength and Microstructure of Ferritic Stainless Steel Single-Lap Joints Brazed with Ni-Based Amorphous Brazing Foils

Abstract

Exhaust gas recirculation (EGR) coolers composed of stainless steel brazed with Ni-based brazing filler metals for motor vehicles are a standard technology. The ferritic stainless steels have been used in the EGR coolers because of the requirement of low material cost compared to austenitic stainless steels for the last decade. On the other hand, Ni-based amorphous brazing foils produced with rapid solidification technology have been increasing since the foils are ductile and do not contain organic binders. Few studies were conducted on the mechanical properties of ferritic stainless steels brazed with Ni-based amorphous brazing foils. This study investigated the shear strength and microstructure of ferritic stainless steel single-lap joints brazed with commercially available Ni-based amorphous brazing foils. As a result, it appeared that the SUS444 single-lap joint brazed with MBF67 brazing foil containing phosphorus had relatively lower shear strength than those brazed with MBF20 and MBF50 brazing foils because of the formation of the Cr-Ni-P intermetallic compounds with higher Vickers hardness within the brazed layer.