The effect of niobium on the microstructure evolution of ferritic stainless steel matrix cermets.

Formation of secondary chromium-rich carbides, resulting in the chromium depletion of metallic binder, is a challenge in the technology of high-chromium steel bonded ceramic-metal composites (cermets, cemented carbides). The present work addresses the effect of strong carbide forming elements, in particular niobium, on the structure formation of straight-chromium stainless steel bonded TiC-FeCr cermets. Cermets were produced using the conventional powder metallurgy pressing and liquid-phase sintering route of cermets and cemented carbides. To study microstructural evolution of cermets scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were used. Results of the research showed that the addition of reasonable amounts of niobium (up to 6 wt%) is insufficient for complete suppression the formation of chromium-rich carbide precipitates. However, the niobium additions enable to reduce chromium depletion of high-chromium steel matrix of TiC-FeCr cermets. [ABSTRACT FROM AUTHOR]