Vacuum brazing of titanium alloy to stainless steel enhance by fiber laser surface texturing

A method for improving the brazing joining strength of Titanium alloy/Stainless steel fabricated through fibre laser surface texturing is introduced because it is a simple process that does not require the fabrication of complicated interlayers. However, previous research shows that a milimeter scale was fabricated by surface modification for dissimilar brazing join, yielding insignificant results and limiting the application and degree of enhancement. Fiber laser ablation was used in this study to create microscale periodic patterns (grooves) on a stainless steel surface. No defect or damage induced during laser surface texturing process. The groove dimension was tunable by controlling the laser parameters. Vacuum brazing of Ti6Al4V to 316L stainless steel with surface texturing, the average joint strength was 22.1 MPa, 34% of increase of joining strength compared to unprocessed flat surface. The combination of laser surface texturing and brazing proven effectively on joining strength enhancement.

Vacuum Brazing of C/C Composite and TiAl Intermetallic Alloy Using BNi-2 Brazing Filler Metal

C/C composite was brazed to TiAl intermetallic compound using a commercial BNi-2 brazing filler metal under vacuum brazing condition. The brazing temperature was 1030~1150 °C and the holding time was 20 min. The joint interfacial microstructures and mechanical properties were studied, and the fracture behavior and joining mechanism were also investigated. The effect of brazing temperature on the joint shear strength was explored. The results showed that a perfect interface joint can be obtained by using BNi-2 to braze C/C and TiAl. During brazing, Ti, Cr, and other carbide forming elements diffused to C/C composite side, forming Cr3C2, Cr7C3, TiC, and other carbides, and realizing metallurgical joining between the brazing filler metal and C/C composite. The microstructure of the interface of C/C composite and TiAl intermetallic compound joint is as follows: TiAl alloy → TiAl + AlNi3 → AlNi2Ti → Ni(s, s) + Ti3Al + Ni3Si → Ni(s, s) + Ni3(Si, B) + CrB → Ni(s, s) + Ni3Si + TiCr2 → (Ti, Cr)C → C/C composite. When the holding time is fixed, with the increase of brazing temperature, the shear strength of the joint increases first and then decreases. The maximum average room temperature shear strength of the brazed joint was 11.62 MPa, while the brazing temperature was 1060 °C and the holding time was 20 min.