High-strength C/SiC joints prepared using a novel Ni-Si-CNTs-based filler

Abstract

A novel brazing formulation with carbon nanotube (CNTs) incorporated in the Ni-30Si alloy is designed to enhance the self-bonding of C/SiC composites. The LSS value and Rockwell hardness of the joint strongly depend on the amount of CNTs added. The joint with a 10 vol% CNTs content performs the best, with an average LSS value of 21 MPa, which is 147% higher than the joint prepared without the addition of CNTs. The enhancement in the joint strength is ascribed to the excellent wettability of filler, formation of new high-temperature resistant phases (e.g. Ni2Si, Ni3Si2, and β-SiC) and a significant reduction in the CTE values causing lower thermal residual stresses while cooling. On the other hand, under excessive CNTs loading (>10 vol%), the joint strength is significantly diminished as a result of agglomeration, void formation, and poor wettability. The fracture surface analysis exhibited substantial CNTs rod pull-out, a phenomenon highly desirable for enhanced bond strength and non-catastrophic failure of the joint. © 2023 Elsevier Ltd