Braze Materials for Brazing Seal Honeycomb: Trends, Challenges and a Market Outlook

摘要

Honeycomb remains a popular material structure to provide gas path sealing in gas turbines. The many seal locations in the compressor and turbine modules of jet engines are reviewed and a basic model of how honeycomb functions in a labyrinth seal design is presented. Standard brazing materials for joining honeycomb to backing members are reviewed. In modern gas turbine engines there is a trend towards higher operating temperatures as increasing the cycle peak temperature helps improve engine efficiency and thereby reduces fuel consumption and CO_2 emissions. In turbine modules, in particular, the increased temperatures challenge the oxidation resistance of brazed seal assembles. This paper reviews high temperature failure mechanisms of honeycomb seals, one of them being braze alloy oxidation induced fatigue, which highlights the need for braze filler materials with improved high temperature oxidation / hot gas corrosion resistance. Other requirements for optimized joining of seal honeycomb include precise metering of the amount of braze filler and the need for high temperature resistant fillers with improved wetting and reduced base metal penetration for honeycomb made from ferritic alloy foils with high aluminum concentration. The demand for braze materials used in joining honeycomb in aero engine seal applications will steadily grow in the next decade, mainly driven by an increased demand for new engines with improved performance.