Structure, hardness and thermal stability of TiAlN and nanolayered TiAlN/CrN multilayer films

TiAlN films were deposited on silicon (1 1 1) substrates from a TiAl target using a reactive DC magnetron sputtering process in Ar + N-2 plasma. Films were prepared at various nitrogen flow rates and TiAl target compositions. Similarly, CrN films were prepared from the reactive sputtering of Cr target. Subsequently, nanolayered TiAlN/CrN multilayer films were deposited at various modulation wavelengths (A). X-ray diffraction (XRD), energy dispersive X-ray analysis, nanoindentation and atomic force microscopy were used to characterize the films. The XRD confirmed the formation of superlattice structure at low modulation wavelengths. The maximum hardness of TiAlN/CrN multilayers was 3900 kg/mm(2), whereas TiAlN and CrN films exhibited maximum hardnesses of 3850 and 1000 kg/mm(2), respectively. Thermal stability of TiAlN and TiAlN/CrN multilayer films was studied by heating the films in air in the temperature range (T-A) of 500-900degreesC for 30 min. The XRD spectra revealed that TiAlN/CrN multilayers were stable up to 800degreesC and got oxidized substantially at 900degreesC. On the other hand, the TiAlN films were stable up to 700degreesC and got completely oxidized at 800degreesC. Nanoindentation measurements performed on the films after heat treatment showed that TiAlN retained a hardness of 2200 kg/mm(2) at T-A = 700degreesC and TiAlN/CrN multilayers retained hardness as high as 2600 kg/mm(2) upon annealing at 800degreesC. (C) 2004 Elsevier Ltd. All rights reserved.