Characterization of Nanostructured NbSi2 Intermetallic Coatings Obtained by Plasma Spraying of Mechanically Alloyed Powders

Abstract

Nanostructured NbSi 2 powders plasma sprayed on to Ti-6Al-4V substrates were characterized in this research. After preparation of the nanostructured NbSi 2 powders by mechanical alloying of an Nb-Si powder mixture, agglomeration was performed to obtain a particle size suitable for spraying. The agglomerated powders were then sprayed by atmospheric plasma spraying. Structural transformation of the powders and morphological and mechanical changes of the coatings were examined by use of x-ray diffraction analysis, scanning electron microscopy, energy dispersive spectroscopy, and microhardness testing. During milling, NbSi 2 intermetallic with a grain size of approximately 15 nm was gradually formed. After plasma spraying, a coating of hardness 550 ± 8 HV with a uniform nanocrystalline structure, low oxide content, low porosity, and a good adhesion to the substrate was obtained. No phase change occurred after spraying and the NbSi 2 compound remained nanostructured with a grain size of approximately 82 nm.

Porosity and Its Significance in Plasma-Sprayed Coatings

“…Thus, the sprayed coatings are made up of the molten powders and some semi-molten powders. It has been noted that these special structures of sprayed coatings benefit the properties of the nanostructured coating, especially the improvement of denser coating with better hardness surface and better strength [110][111][112].…”

Porosity and Its Significance in Plasma Sprayed Coating: A Review

“…Thus, the sprayed coatings are made up of the molten powders and some semi-molten powders. It has been noted that this special structures of sprayed coatings benefit the properties of nanostructured coating, especially the improvement of denser coating with better hardness surface and better strength [93][94][95].…”