Hard and superhard nanocomposite Al–Cu–N films prepared by magnetron sputtering

The article reports on structure, mechanical properties and macrostress of Al–Cu–N films deposited by reactive sputtering using a dc unbalanced magnetron equipped with a round planar aluminum target fixed to the magnetron cathode with a copper ring. A systematic investigation of sputtered films showed that: (i) Al–Cu–N is a new nanocomposite material which can form superhard (>40 GPa) coatings with a maximum microhardness of approximately 48 GPa; (ii) Al–Cu–N can easily form a very fine-grained material; (iii) the size of grains decides on the macrostress in Al–Cu–N films; the Al–Cu–N films composed of grains with the average size of 9.5 nm exhibit a low (<0.5 GPa) macrostress and, on the contrary, the Al–Cu–N films composed of larger (>10 nm) grains exhibit large macrostress of several GPa; and (iv) the macrostress in Al–Cu–N films can be varied from tension to compression by the variation of the energy delivered to the growing film, i.e. by the ion bombardment and the substrate heating. The relationships between microhardness, H, Youngʹs modulus, E, and elastic recovery, We evaluated from loading/unloading curves measured using the microhardness tester Fisherscope H 100 are also given.