Microstructure and properties of pressure-less joining of SiCf/SiC composites by Ti–Si alloys

Abstract

Prepared with pure Ti and Si powders as raw materials, the Ti16Si84 alloy (at. %) was obtained through refining in an intermediate frequency magnetic induction furnace. In this study, a novel method to join SiC fiber-reinforced SiC matrix composites (SiCf/SiC composites) under non-pressurized conditions is proposed using Ti16Si84 alloy foil as the joining material. The joining process was optimized, and the wettability, microscopic morphology, and bonding reaction of the joint were studied, along with the fracture characteristics and the bonding mechanism. Additionally, the corrosion resistance of the joints was examined in pure static water with high-dissolved oxygen (246 ppm) at 360 °C and 18.6 MPa. The results showed that Ti16Si84 alloy has good wettability with SiCf/SiC, enabling it to join SiCf/SiC successfully. The joint was composed of SiC, TiSi2, and Si, and there was no intermediate between them. When the brazing temperature was 1410 °C, the shear strength of the joint reached 42.5 MPa, and the joint integrity was favorable. After the shear test, numerous SiCf/SiC composites were torn by the solder, indicating their advantageous shear properties and high joint strength. After three days of corrosion, the joint samples' weight showed almost no changes. The corrosion depth was less than 20 μm and the residual shear strength of the corroded joined samples was 38.37 MPa, indicating excellent hydrothermal corrosion resistance of the joint material.