Brazing of C/C Composites and Ni Base Alloys With Ag-Cu-Ti and Fe-Based Braze Filler Alloys

摘要

Carbon/carbon composites have high specific strength and high heat resistance. To utilize its high heat resistance, it has been brazed to the heat resistance alloys using Ni-base brazing alloys. In this research, the feasibility of using Ag-Cu-Ti and Fe-based brazing filler alloys to braze C/C composites and Ni-base heat resistance alloys, Inconel 600 and Hastelloy C-276, and the austenitic stainless steel, SUS304, is investigated. The Ag-Cu-Ti brazing filler was 63.63Ag-34.65Cu-1.72Ti (Cusil-ABA~®, Morgan Ceramics), and the Fe-based brazing filler alloy was Fe-20Cr-42-Ni-12(Si+P) (TB-2720, Tokyo Braze). To relieve the residual stress induced by the mismatch in the coefficient of thermal expansion (CTE), an interlayer was added to some of the brazing specimens that consisted of inserting either a piece of Ni foil or a piece of Cu foil at the brazing interface. The samples were brazed in a vacuum furnace at a brazing temperature of 830℃ for the Ag-Cu-Ti brazing filler alloy and 1070℃ for the Fe-based brazing filler. The microstructure of the brazed interface was observed using an optical microscope and SEM. It was found that brazed joints were obtained for the combinations of C/C composites / Cu foil / Inconel 600 and C/C composites / Cu foil / Hastelloy C-276, both of which were brazed with Ag-Cu-Ti brazing filler alloy. The brazed joints of the other combinations could form a bond between the C/C composites and the brazing filler layer, but later cracked upon cooling.