Magnetron sputtered nanocrystalline metastable (V,Al)(C,N) hard coatings

Nanocrystalline hard coatings of the system V-Al-C-N with an f.c.c. metastable solid solution (V,Al)(N,C) microstructure were deposited by non-reactive r.f.-magnetron sputtering of a ceramic compound target (composition: 60 mol.% VC and 40 mol.% AIN) in a pure argon discharge at 1.1 Pa. The chemical composition of the as-deposited coatings was determined by electron probe micro analysis (EPMA). The microstructure of the thin films was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The influence of a moderate argon ion bombardment during thin film deposition, realized through the variation of the argon ion energy in the range 20 eV-170 eV, as a means to adjust the adatom surface mobility and surface diffusion processes, on the microstructure evolution and on the Vickers micro-hardness is discussed. The conditions for the formation of a metastable solid solution f.c.c. (V,AI)(C,N) thin film microstructure are described in terms of surface processes during film growth and thermodynamic considerations. It was demonstrated, that a metastable phase formation in the quaternary material system V-Al-C-N can easily be adjusted in magnetron sputter deposition.