MECHANICAL-PROPERTIES AND MICROSTRUCTURES OF POLYCRYSTALLINE CERAMIC-METAL SUPERLATTICES - TIN/NI AND TIN/NI0.9CR0.1

Polycrystalline superlattice coatings of TiN/Ni and TiN/Ni0.9 Cr0.1 of thickness 2-3 mum were deposited onto tool steel substrates using an opposed-cathode reactive unbalanced magnetron sputtering system. The TiN/Ni superlattices have repeated periods (LAMBDA) from 1.8 to 62 nm with various Ni layer thickness (l(Ni)) to LAMBDA ratios, l(Ni)/LAMBDA. TiN/Ni0.9Cr0.1 superlattices have LAMBDA = 1.2-7.4 nm with l(NiCr)/LAMBDA = 0.3. The structures were analyzed by X-ray diffraction, as well as plan-view and cross-sectional transmission electron microscopy. The hardnesses and elastic moduli of the superlattices were measured using nanoindentation techniques. An increase in hardness with decreasing LAMBDA and grain size was observed. A maximum hardness of 3500 kgf mm-2 for TiN/Ni, about 1.5 times of the rule-of-mixtures values, was found at l(Ni)/LAMBDA = 0.16 and LAMBDA = 2.2 nm. For TiN/Ni0.9Cr0.1, a maximum hardness of 3200 kgf mm-2 was found at l(Ni)/LAMBDA = 0.3 and LAMBDA = 1.2 nm. No significant variations in TiN/Ni0.9Cr0.1, film modulus were found as a function of LAMBDA.