Characterization of nanostructured TiN coatings fabricated by reactive plasma spraying

The nanostructured TiN coatings are fabricated by means of reactive plasma spraying micrometers titanium powders in the atmosphere, and the microstructure and performance of the coatings are analyzed by XRD, SEM and TEM. The experimental results show that the coatings are mainly composed of TiN and Ti3O phases, and the coatings have the typical sprayed lamellae structures. In parallel to substrate surface direction, the nanoscale grains with particle diameters ranging from 60 to 120nm are observed in the coatings, and both fine equiaxed and columnar grains are found in some zones of the nanostructured TiN coatings. But in vertical to substrate surface direction, the contrary is the case. Thus it can be concluded that the TiN coatings are composed of the columnar grains, and the columnar grains are nanostructural equiaxed grains in their cross-section. In addition, a large number of deformation twins caused by the stresses concentration are found in TiN coatings. Meanwhile, the nanostructured TiN coatings have a higher bonding strength and better fracture toughness than other observed as-sprayed coatings.