A new method for isolating plasma interactions from those of the laser beam during plasma nitriding

摘要

AbstractA new method for separating the interactions of a laser plasma from those of a laser beam with a titanium substrate was developed. A laser-sustained plasma (LSP) was generated by striking the plasma on a titanium plate in a flowing nitrogen atmosphere at ambient pressure and subsequently removing the strike plate. The resultant nitrogen plasma was sustained indefinitely around the laser focal plane until the nitrogen gas flow and/or the laser power were switched off. The laser-sustained nitrogen plasma was then used as a “reactor” to study the effects of a nitrogen plasma, independent of the laser beam, when the plasma was brought into close proximity, (2 to 3mm), parallel to a titanium substrate. There was no interaction of the parallel laser beam with the substrate. Heat, nitrogen and titanium were exchanged between the nitrogen LSP and substrate resulting in melting, nucleation and growth of faceted and dendritic TiN crystals, rectangular hollow TiN morphologies and particulate TiN deposits. Dense TiN layers up to 300μm thick formed within 5s. The results demonstrated that compositionally graded layers of nitrogen-enriched titanium, and titanium nitride could be formed very rapidly on model, commercially-pure titanium substrates, with promise for extension to commercial alloys such as Ti-6Al-4V.Graphical AbstractA method for separating the interactions of a laser plasma from those of a laser beam with a Ti substrate is discussed in this paper. Heat, nitrogen and titanium were exchanged between a nitrogen laser-sustained plasma and the substrate resulting in melting, nucleation and growth of dendritic and faceted crystals, hollow, rectangular TiN morphologies, and particulate TiN deposits. A dense TiN surface layer, up to 300μm thick, formed within 5s.Display OmittedHighlights?Nitriding of titanium was studied using a laser sustained plasma (LSP) reactor, independent of the laser beam.?Nucleation and growth of faceted, dendritic, rectangular and particulate TiN morphologies was observed.?TiN layers up to 300μm thick formed within 5s - one of the most rapid TiN growth rates observed for LSP/laser nitriding.?LSP accessed novel microstructures compared to laser nitriding with or without surface-struck plasm plasma.]]>