Metal dusting of ferritic Fe–Ge in the absence of cementite

Iron and Fe–10 wt.% Ge alloy were exposed at 680 °C to reducing, carbon-supersaturated CO–H2–H2O gas (ac = 2.9). Iron grew into a cementite scale which disintegrated into nanoparticles as graphite deposited from the gas and grew into the Fe3C. The Fe–Ge alloy formed no Fe3C, and carbon deposited directly on the metal surface. As the graphite grew into the metal, ferrite nanoparticles were dislodged from the surface into the carbon. Metal consumption and carbon nanotube growth were more rapid in the latter case.