We have developed a novel processing technique to fabricate tungsten carbide (WC) nanocomposites with uniform grain size. In this method, pulsed laser deposition of WC in conjunction with a few monolayers of nickel aluminide (NiAl) is used to control the grain size of nanocrystalline composites. The grain size of WC was controlled by the thickness of tungsten carbide and the substrate temperature. The role of NiAl is to ensure the nucleation of tungsten carbide islands, and it is relatively insoluble in WC. Using this approach, we have fabricated nanocomposites of grain sizes ranging from 6 nm to 35 nm. The hardness of the composite increases with the decrease in grain size, following approximately Hall-Petch relationship. Below a critical value, we observed a softening behavior which has been modeled to be related to intragrain deformation or grain boundary shear. The role of NiAl in grain boundary deformation is of particular interest in strengthening and stabilizing against the grain growth of nanocrystalline composites. The new WC-NiAl composite is expected to have superior high-temperature strength compared to conventional microcrystalline WC-Co composites.
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Novel Nanocrystalline Composites
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Narayan, J. "Novel Nanocrystalline Composites." Proceedings of the ASME 2002 International Mechanical Engineering Congress and Exposition. Materials: Processing, Characterization and Modeling of Novel Nano-Engineered and Surface Engineered Materials. New Orleans, Louisiana, USA. November 17–22, 2002. pp. 297-301. ASME. https://doi.org/10.1115/IMECE2002-39371
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