NANOINDENTATION AND FRICTION STUDIES ON TI-BASED NANOLAMINATED FILMS

Multilayered Ti/TiN and Ti/Cu films of 12-15 mu M thickness were produ ced using an r.f, triode-magnetron sputtering technique. The thickness of Ti layers in both types of composites varied between 150 and 1000 nm. TiN and Cu layers were thinner, and their thicknesses varied withi n a narrower range of 20-120 nm. The volume fractions of the constitue nts in the composites were kept constant in order to study the effect of reducing Ti layer thickness (lambda,(Ti)) on the mechanical and tri bological properties of the laminates. Nanoindentation tests were perf ormed to determine hardnesses and elastic moduli of the composites and to analyze the energy expenditure during the indentation process. The elastic modulus and hardness of the Ti/TiN alms were both higher when tested in a direction parallel to the plane of the layers compared to a direction normal to their planes. The strength of Ti/TiN also incre ased with (lambda(Ti))(-0.5) and showed a good agreement with the stre ngth levels calculated by considering the difference in the elastic mo duli of the constituents on the basis of the Koehler strengthening mec hanism. Thin Cu layers in Ti/Cu were not effective as barriers to disl ocation motion, and Ti/Cu interfaces were susceptible to delamination during indentation tests and sliding wear tests. A linear relationship was observed between the wear rates of Ti/TiN and (lambda(Ti))(-0.5) which suggests that the wear resistance of the laminated composites ca n be improved by reducing the distance between the TiN layers.