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TiN/CrN superlattices; d.c. reactive magnetron sputtering; structural and mechanical properties; nanoindentation; AFM.

Multilayer superlattice coatings of TiN/CrN were deposited on silicon substrates using a reactive d.c. magnetron sputtering process. Superlattice period, also known as modulation wavelength (𝛬), was controlled by controlling the dwell time of the substrate underneath Ti and Cr targets. X-ray diffraction (XRD), nanoindentation and atomic force microscopy (AFM) were used to characterize the films. The XRD data showed 1st and 2nd order satellite reflections along the principal reflection for films having 132 Å $\geq \Lambda \geq$ 84 Å, thus confirming the formation of superlattice. The multilayer coatings exhibited hardness (𝐻) as high as 3200 kg/mm², which is 2 times the rule-of-mixtures value (i.e. $H_{TiN}$ = 2200 kg/mm² and $H_{CrN}$ = 1000 kg/mm²). Detailed investigations on the effects of various process parameters indicated that hardness of the superlattice coatings was affected not only by modulation wavelength but also by nitrogen partial pressure and ion bombardment during deposition.

Harish C Barshilia¹ K S Rajam¹

1. Surface Engineering Division, National Aerospace Laboratories, Bangalore 560 017, India

Published

February 2003

Manuscript received

26 June 2002

Manuscript revised

4 December 2002