Improved Mechanical Properties of Cermet Coatings As a Function of Grain Size

Thermal sprayed coatings produced from ultrafine- and nano- and near-nano grained powders of tungsten carbide-10 wt.% cobalt-4 wt.% chromium (WC-10Co-4Cr) and tungsten carbide-12 wt.% cobalt (WC-12Co) are believed to provide improved properties as compared to conventional powders.  These materials show great potential for applications in the aerospace industry.  A study is proposed to investigate the influence of WC grain size on thermal sprayed coating properties.   Thermal spray coatings will be produced from powders consisting of grains of WC from micron- to near-nano in size in a Co-matrix and Co-Cr matrix.   The Hall-Petch relationship cites the strengthening of materials by reducing the average crystallite (grain) size.  An Investigation will be conducted on thermal sprayed coatings using these materials with High Velocity Oxy-Fuel (HVOF) deposition.  An examination of consolidated forms will also be performed using the same powders used in thermal spray in the spark plasma sintering (SPS) consolidation.  Improvements observed in the HVOF spray coatings in ultrafine, near-nano, and nano-grained coatings will be compared to those of conventional WC-Co and WC-10Co-Cr powders and coatings.  The mechanical properties of thermal spray coatings have been reported to relate to those of bulk materials.  A comparison will be provided between the properties of thermal spray coatings of these materials and of bulk samples.