No abstract

Nanoindentation was used to study the mechanical properties of Ag/Ni multilayered thin films. Both the hardness and the elastic modulus of the multilayered thin films had values between those for homogeneous Ag and Ni thin films. The trend in the hardness with layer repeat length can be explained by the effects of both the stress and the microstructure. No evidence for interfacial effects on hardness was found. A decrease in modulus at the smallest repeat lengths was compared with literature data on the elastic constants of Ag/Ni multilayers.

Using an are-discharge method, we deposited a diamond-like carbon film 600 nm thick on hardened steel. Characterization of the film was carried out with Raman spectroscopy. In dry sliding wear and friction tests, with a hardened steel pin as a counterpart, we obtained a friction coefficient between 10000 and 20000 cycles, with the maximum value of 0.18. The value decreased to 0.12 after about 100000 cycles. We obtained a wear coefficient of 7 × 10−17 m3/mN. A transfer layer formed on the pin during sliding and probably had the dominating effect on the tribological behavior. We observed in nanoindentation measurements that the film softened in a wear track during the first 20000 cycles. Although fracture pits on the wear track occurred, fracture is not the dominant failure mechanism of these films. Degradation of good tribological properties was caused mainly by partial wear-through of the film after 370000 cycles and by a subsequent redeposition of the transfer film on the wear track during prolonged sliding.

No abstract

Epitaxial TiN/Vo.3Nbo.7N superlattices with a 1.7% lattice mismatch between the layers were grown by reactive magnetron sputtering on MgO(OOl) substrates. Superlattice structure, crystalline perfection, composition modulation amplitudes, and coherency strains were studied using transmission electron microscopy and x-ray diffraction. Hardness H and elastic modulus were measured by nanoindentation. H increased rapidly with increasing A, peaking at H values -75% greater than rule-of-mixtures values at A ~ 6 nm, before decreasing slightly with further increases in A. A comparison with previously studied lattice-matched TiN/Vo.6Nbo.4N superlattices, which had nearly identical composition modulation amplitudes, showed a similar H variation, but a smaller H enhancement of =50%. The results suggest that coherency strains, which were larger for the mismatched TiN/Vo.sNbojN superlattices, were responsible for the larger hardness enhancement. The results are discussed in terms of coherency strain theories developed for spinodally decomposed materials. Nanoindenter elastic modulus results showed no significant anomalies. Downloaded: 21 Mar 2015 IP address: 169.230.243.252 P. B. Mirkarimi et al.: Structure and mechanical properties of epitaxial TiN/Vo.3Nt>o.7N(1OO) superlattices