Brazing SiC matrix composites using Co-Ni-Nb-V alloy

Abstract

Co-13.5Ni-16.2Nb-10 V (wt.%) filler alloy was designed for joining silicon carbide (SiC) matrix composites, including Cf/SiC and SiCf/SiC composites. The wettability of the Co-Ni-Nb-V alloy on two kinds of composites was studied by the sessile drop method. After heating at 1573 K for 20 min, the new filler alloy exhibited a low contact angle of 18° and 2° on the Cf/SiC and SiCf/SiC composite, respectively. The interfacial microstructure was investigated by SEM equipped with EDS. At the interface between the Cf/SiC composite and the brazing alloy, sandwiched reaction band VC/NbC/VC was formed. In the case of SiCf/SiC, only VC band was formed at the interface, signifying that the activity of Nb was lower than V. The elements of Co and Ni mainly existed in the form of Co-Si or (Co,Ni)-Si compound. The Co-Ni-Nb-V alloy was fabricated into the filler foils with thickness of 100 μm by rapid solidification technique. The Cf/SiC-Cf/SiC joints and SiCf/SiC-SiCf/SiC joints were produced using the filler foil at 1553 K for 10 min. The bend strength of the Cf/SiC-Cf/SiC joints brazed with double-layer filler foil is 21.3 MPa tested at room temperature, whereas the maximum strength of the SiCf/SiC-SiCf/SiC joints brazed with single-layer filler foil reaches 30.8 MPa.