Cr2N-7Ag nanocomposite thin films deposited on Vanadis 6 tool steel

Abstract

• Addition of 7 wt.% Ag does not alter the thickness/growth rate of Cr 2 N-film. • The Cr 2 N-7Ag film grows in columnar manner, with presence of individual Ag grains. • Addition of 7 wt.% Ag has not detrimental effect on mechanical properties of Cr 2 N. • Ag-redistribution in Cr 2 N-matrix increases with increasing annealing temperature. • The silver is in a very weak stress state after deposition at 500 °C. Cr 2 N-7Ag self-lubricating nanocomposite thin films were deposited on substrates made of Cr-V ledeburitic tool steel Vanadis 6 by reactive magnetron sputtering at a deposition temperature of 500 °C, using pure Cr and Ag targets, in a composite low pressure N 2 /Ar atmosphere. The films are composed of Cr 2 N-matrix and Ag grains. The films have an average thickness of 4.3 μm. They grew in a columnar manner, but, individual silver agglomerates were visible along the columnar crystals, also. The average size of silver agglomerates lies well below 50 nm. The nanohardness of the Cr 2 N-7Ag films was 16.17 ± 1.93 GPa, e.g. it was practically the same as for the pure Cr 2 N so for Cr 2 N-3Ag coatings analyzed recently. Also, the Young modulus was not negatively affected by elevated silver content. The coatings exhibited good adhesion on the substrate – the first critical loads, established by scratch-testing method, ranged between 31 and 37 N. Annealing of the films at temperatures below the deposition temperature induced only very limited silver redistribution throughout Cr 2 N-matrix. The film annealed at 500 °C manifested more remarkable Ag-redistribution, being represented by the decrease in population density of Ag-agglomerates on the surface and by the decrease in silver content towards to film/substrate interface. Obtained results infer that there is a good opportunity to design the Cr 2 N-Ag film for specific tribological applications, through proper choice of the deposition temperature.