Layered-Fiber Composite with a Niobium-Based Matrix Reinforced with Carbon Fibers

A technological scheme for producing a high-temperature layered-fibrous composite material by solid-phase diffusion welding in vacuum under load from a workpiece with initially layered components—niobium foils and unidirectionally oriented carbon fibers—is presented. The composite structure was formed in two stages. After the first stage, the structure was monitored for the connectivity of its components. Then the second-stage heat treatment was performed, completing the technological process. The longitudinal and transverse structure of the composite was studied using a scanning electron microscope equipped with an energy-dispersive microanalyzer. Data were obtained on the distribution of niobium and carbon in the cross section. The structure includes layers of solid solutions of carbon in niobium, Nb–C intermetallic compounds, and carbon fibers. Composite samples were tested under bending conditions, and the dependence of their strength on temperature in the range of 20 to 1400°C was obtained. The strength values correspond to the requirements for structural materials used in parts for the high-temperature circuit of gas turbine engines. The stress–strain curves showed the non-brittle failure of the composite material containing brittle components (intermetallic compounds and carbon fibers), which was also confirmed by the morphology of the fracture surfaces.