Contact reactive brazing of TC4/304 stainless steel dissimilar metals by interrupted arc pulsed welding

Abstract

The most challenging aspect of producing durable joints between titanium alloy and stainless steel (Ti/SS) is preventing the formation of brittle Ti–Fe intermetallic compounds, particularly the TiFe2 phase. In this paper, the interrupted pulsed arc welding (IPAW) was proposed to join TC4 and 304SS dissimilar metals. The joining mechanisms, microstructures and shear strength of the joints were investigated. The precise regulation of arc pulsed time in the millisecond range enabled the creation of a joint without the formation of the TiFe2 phase through contact reactive brazing. A Ti-rich reaction layer consisting of β-Ti and TiFe phases was formed in the brazing joint, and the shear strength of the joint reached 106.3 MPa. By increasing the arc pulsed current or time, the brazing joint was transformed into the fusion joint. The formation of two reaction layers was observed: Ti-rich phases (TiFe and β-Ti) near the TC4 and Fe-rich phases (TiFe2 and TiCr2) near the 304SS, which exhibited high brittleness. The presence of a high brittleness fusion zone resulted in immediate cracking post-welding.

Keywords

• Titanium alloy
• Stainless steel
• Dissimilar metal welding
• Arc welding
• Microstructure