Electrospun carbon nanofiber membranes for reinforcing YG8-GH3536 vacuum brazed joints

Abstract

YG8 cemented carbide and GH3536 alloy vacuum brazed joints always suffer from high residual stress and poor toughness. To tackle this, we innovatively combined and employed electrospinning and carbonization to produce a carbon nanofiber (CNF) intermediate brazing interlayer membrane. The CNF interlayer effectively alleviated residual stresses and improved the overall mechanical performance of the joint. The morphology and crystallinity of the CNF membrane were characterized and correlated to effects on the microstructure and mechanical performance of the joint. Findings demonstrate that the CNF interlayer significantly reduced the amount of brittle intermetallic compounds in the braze seam, while increasing the proportion of Ag-Cu eutectic composition. The CNF framework remained intact after the brazing procedure and enhanced joint strength and toughness through load transfer and stress relief due to the fine and uniformly distributed porous microstructure. Compared to direct brazing without the CNF interlayer, the interlayer caused remarkable improvements: at room temperature, shear strength and fracture toughness increased by 43 % and 82 %, respectively, while at elevated temperature (400 °C), the corresponding enhancements reached 79 % and 263 %. In addition, finite-element analyses show that the residual stress in the joint could be markedly relieved after the introduction of an CNF interlayer due to its low coefficient of thermal expansion. This work provides an effective strategy for optimizing dissimilar material joints in extreme environments, particularly for space exploration applications.