Influence of Al and Si content on structure and mechanical properties of arc evaporated Al–Cr–Si–N thin films

• Synthesis of AlCrSiN films by reactive arc evaporation from AlCrSi targets
• Nanocomposite structure of fcc Al–Cr–(Si)–N grains surrounded by a-SiNx
• Reduced grain size as a result of increased SiNx phase fraction
• Highest hardness obtained for 4 at.% Si in the coating

The effect of Al and Si on development of structure and mechanical properties was studied for arc evaporated Al–Cr–(Si)–N films synthesized from Al–Cr and Al–Cr–Si composite targets. All films show stoichiometric compositions, with a Si content corresponding to the target and a minor loss of Al. The hardness of Al–Cr–N films reaches a maximum for Al/Cr ratios close to the solubility limit of AlN in CrN. The addition of Si results in a further increase of hardness due to solid solution hardening and formation of a nanocomposite structure, which is accompanied by a reduced crystallinity and grain size. Al–Cr–Si–N films with high Si contents show a reduced hardness due to grain boundary sliding promoted by the higher amorphous phase fraction.