Structural characterization and mechanical properties of plasma sprayed nanostructured Cr2O3-Ag composite coatings

In the present study, nanostructured Cr2O3-Ag composite coatings were fabricated by plasma spraying technique and their surface characteristics and mechanical properties were evaluated as a means of improving the tribological performance. For this purpose, Cr2O3 and various amounts of silver nanoparticles (0%, 2%, 5%, and 10), as a solid lubricant phase, were agglomerated into appropriate feedstock powders and plasma spraying parameters were controlled to produce nanostructured composite coatings. The microstructure of coatings was examined by a scanning electron microscope (SEM), phase composition by X-ray diffraction (XRD) and distribution of chemical composition through the thickness by energy dispersive spectroscopy (EDS). The influence of nanostructure on mechanical properties, including hardness and toughness, was evaluated by indentation testing. Uniform distribution of Ag nanoparticles was obtained in Cr2O3-2% Ag and 5% Ag specimens, but accumulation of Ag nanoparticles was observed within interlamellar regions of Cr2O3-10% Ag coating. The presence of nanoparticle zones, comprising 15–18% of the surface area, was observed on the cross sections of the specimens; these zones caused a reduction in lamella thickness and increased the fracture toughness by arresting crack tips.