Structure-hardness relations in sputtered Ti–Al–V–N films

Abstract The paper presents a detailed analysis of structure-hardness relations in hard and superhard nanostructured Ti(Al,V)N x films with a low content of Al (5 at.%) and V (2 at.%). The Ti(Al,V)N x films were prepared by d.c. reactive magnetron sputtering. Special attention is devoted to the energy E pi delivered to the growing film by bombarding ions. It was found that (1) Ti(Al,V)N x films form a superhard material with hardness H ≥40 GPa; (2) superhard Ti(Al,V)N x films are: (i) poly-oriented films characterized with at least two broad, low-intensity X-ray reflections, i.e. are composed of small grains of different crystallographic orientations; (ii) exhibit a low compressive macrostress σ ≤−2 GPa; and (iii) formed at higher values of E pi ≥0.5 MJ/cm 3 and low values of a total sputtering gas pressure p T ≤0.5 Pa; (3) a minimum energy E pi min , which is needed to form the superhard film, is a necessary condition but not the sufficient one; (4) the superhard films with a maximum hardness are characterized by the optimum structure which is formed if sufficient energy E pi ≥ E pi min =0.5 MJ/cm 3 is delivered. The main result of this study is finding that nanostructured materials can be superhard also in the case when they are composed of small grains of the same material but of different crystallographic orientations .