Graded metal-carbide composites produced by solid state transformations in VC-coated Ni

Graded metal-carbide composites were produced by solid state transformations in Ni samples, which were coated with VC by thermally activated chemical vapor deposition (CVD) onto a Ni substrate, followed by heat treatments. CVD produced a multi layer coating, an inner M2C layer and an outer V-Ni-C solid solution, with randomly dispersed M2C particles. Also, a V enriched Ni substrate converted to Ni2V and/or Ni3V intermetallics, up to a depth of about 15 μm. Further heat treatments reduced the amount of intermetallics, and precipitated M8C7 that increased with time. These phase transformations were very intense above the order-disorder transformation temperature for the Ni3V intermetallic (1045 °C), and drastically changed the microstructure, producing a cermet layer, i.e., M8C7 precipitated particles in a Ni matrix. The observed microstructural modifications suggest the possibility of tailoring a graded material for wear control, conformed by an external thin carbide layer, followed by a thicker cermet zone.