Nanolayered TiN/NbN multilayers as new superhard materials

We have deposited nanolayered multilayer coatings of TiN/NbN on silicon and tool steel substrates using a reactive DC magnetron sputtering process. Judicious control of process parameters enabled to deposit stoichiometric TiN/NbN coatings. The bilayer thickness, also known as modulation wavelength (), critically affected the properties of the coatings. Coatings deposited at 150 Å 30 Å exhibited superlattice structure in XRD data. Nanoindentation data indicated that polycrystalline TiN/NbN multilayers exhibited hardness as high as 4000 kg/mm2, which was ~2 times the rule-of-mixtures value. Annealing of the coatings in vacuum indicated that coatings retained superlattice structure even up to 850°C. Furthermore, the multilayer coatings showed a tremendous improvement in the corrosion resistance in 0.5 M HCl solution as compared to the single layer TiN and NbN coatings