Abstract
Hardcoatings of WC/12Co and Al2O3/13TiO2, produced by High Velocity Oxy-Fuel (HVOF) and High Energy Plasma (HEP) spraying, have been investigated. In HVOF spraying, nanostructured WC/Co coatings experience more extensive decarburization than conventional coatings, whereas in HEP spraying, just the opposite effect occurs. This is explained in terms of the influence of temperature on the decarburization mechanism. In the Al2O3/13TiO2 case, HEP spraying generates a metastable coating, due to rapid quenching of the plasma melted particles on the substrate. The metastable phase has a defect spinel structure and a nanocrystalline grain size. When heated, it decomposes into an equilibrium two-phase structure, consisting of α-Al2O3 and β-Al2O3.TiO2. Both nanostructured cermets and ceramics have potential as wear-resistant coatings.
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