Novel Ni-Cr-C alloys with chromium carbide whiskers

We study the phases forming in the Ni–Cr–C three-component system appearing during powder mixture baking at 1200–1300 °C followed by fast cooling under increasing the concentration of a graphitic component (up to 5 wt%). The resulting multiphase new alloys show distinctive crystalline Cr 3 C 2 rods with 1–10 micrometer diameters. The whisker regions in alloys have an extremely high hardness from 2200 up to 3200 HV (comparable to the highest hardness of nano whiskers and coatings with the presence of chromium carbide nanoinclusions). We formulate a sol–gel chemistry mechanism of rod formation via carbon diffusion into Cr and Cr x C y through a softened Ni-C particle on the Cr particle and the top of growing whisker. It explains discovered correlation between whisker diameters and Ni-particle sizes.