Effect of TIG Welding Temperature Field on Microstructure and Mechanical Performance of Dissimilar Stainless Steel Brazing Joint

For the manufacture of a liquid rocket engine combustion chamber, the dissimilar stainless steels 1Cr18Ni9Ti and 1Cr21Ni5Ti were firstly brazed with Mn-based filler metal. And then, TIG welding was performed at the side of the 1Cr21Ni5Ti outer wall. Moreover, the effects of TIG welding parameters on the microstructure and properties of the brazed joint were studied. The results indicate that the weld zone of the dissimilar stainless steel joint brazed by Mn-Ni-Cr filler metal is mainly composed of Fe-Ni-Mn ternary solid solution. After TIG welding, the 1Cr18Ni9Ti inner wall undergoes recrystallization softening, while the dual-phase 1Cr21Ni5Ti outer wall undergoes phase transformation, and the microstructures of the base metals are degenerated. In addition, the C atom in the steels migrates to the welding interface at high temperature to form Cr-rich and Ti-rich carbides, which increases the risk of rapid propagation along the interface after crack initiation. Therefore, under the influence of TIG welding temperature field, the mechanical properties of the brazed joint of the dissimilar stainless steel show a downward trend.