Vacuum brazing TiAl intermetallics to GH3030 alloy with a multi-component Ti-based filler metal

Abstract

TiAl intermetallics was vacuum-brazed to GH3030 alloy with multi-component Ti-based amorphous filler metal (Ti 36.1 Zr 11.1 V 2.8 Cu 38.9 Ni 5.6 Al 2.8 Co 2.8 , at.%). The effect of brazing temperature on the microstructure evaluation and shear strength of TiAl/GH3030 brazed joint was studied. The brazed seam presented sectionalized feature with the formation of four reaction zones. Two transition zones with linear growth formed respectively adjacent to two base metals due to elemental solid-state diffusion from the filler metal to base metals. Increasing the brazing temperature accelerated the diffusion between the filler metal and base metals. And those two transition zones thickened, as well as the middle zone composed of primary phase and (Ti, Zr)(Al, Cu, Ni) matrix. Blocky primary phase Ti(Al, Cu, Ni) 3 in middle brazed seam increased, thinning the Ti(Ni, Cu) reaction layer. The maximum shear strength of the brazed joint was obtained at 990 °C. During the shear test, the cracks of the brazed joint propagated along the interface of the transition zone/middle brazed seam at TiAl base metal side on account of the stress concentration and the formation of Ti(Al, Cu, Ni) and Ti(Al, Cu, Ni) 3 at two sides of the fractured interface. And the failed joint exhibited layered fracture surfaces and brittle fracture feature.