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 initial layer-by-layer components — niobium foils and unidirectionally oriented carbon fibers is presented. The procedure for forming the composite structure was carried out in two stages with the structure being monitored after the first stage for the connectivity of its components, and then heat treatment of the second stage was performed, completing the technological process. The longitudinal and transverse structure of the composite was studied using an electron scanning 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 specimens were tested under bending conditions and the dependence of their strength on temperature in the range of 20°C—1400°C was obtained. The strength values correspond to the requirements for materials of this kind, intended as structural ones for the manufacture of parts for the high-temperature circuit of gas turbine engines. Analysis of the stress-strain curves obtained as a result of testing the specimens showed the non-brittle nature of the destruction of the composite material containing brittle components — intermetallic compounds and carbon fibers — which is also confirmed by the morphology of the fracture surfaces of the specimens.

niobium, carbon fibers, solid solution, structure, interface, fracture toughness, temperature, strength, fracture