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Reactive magnetron sputtering was used to deposit coatings from a 304 stainless steel target (nominal composition 18%Cr, 8% Ni, balance Fe). Deposition was carried out in a mixed argon/nitrogen atmosphere with Ar:N 2 ratios of 4, 1.5 and 1, and a total gas flow of 25 sccm for all cases. Substrate temperatures ranged from 150 to 600 °C, along with substrate bias levels from − 100 V to − 140 V. X-ray diffraction analyses showed the structure of the coatings were strongly temperature dependent: above 450 °C, the films were a mixture of CrN, bcc-Fe and Ni; below 450 °C the S-phase (a N-supersaturated fcc structure) was observed. While this structure is nominally cubic, the commonly observed anomaly of ( hkl )-dependent lattice constants, where a 200 > a 111 , was also found in the present study. Area-detector based X-ray diffraction studies, which allowed peak position measurements as a function of the inclination of the diffraction vector (angle ψ), showed a 200 declined with increasing ψ, but always remained greater than a 111 , which was relatively constant with ψ. SEM cross-sections for samples deposited below 450 °C had discontinuous, angular crystallites, whereas at higher substrate temperatures the structure had the appearance of a loose particle aggregate. At higher nitrogen has concentrations (Ar:N 2 of 1:1) a more typical columnar structure was found. Hardness testing gave values between 450 and 1968 kg/mm 2 , with higher bias, temperatures and N 2 gas concentrations promoting higher hardness levels.

This study examines the structure and properties of stainless steel coatings deposited to incorporate large concentrations of nitrogen along with varying amounts of titanium. Deposition was carried out using magnetron co-sputtering of stainless steel and titanium from separate targets in a mixed Ar/N2 gas atmosphere. Composition analysis by X-ray photoelectron spectroscopy showed that while films with up to 4 at.% Ti exhibited little change in nitrogen content (compared to films deposited without Ti) and remained sub-stoichiometric with respect to N content. Films with 7&ndash, 8 at.% Ti had a higher N level and further increasing the Ti level to 11&ndash, 12 at.% resulted in stoichiometric N levels. X-ray diffraction showed that the films all had a nominally FCC structure with no additional phases. However, the peak locations for the (111) and (200) reflections indicated a distorted lattice characteristic of the S-phase, with calculated c/a values ranging from 1.007 to 1.033. The Ti additions, along with the corresponding increase in N content, helped reduce the extent of lattice distortion. The film microstructure of the higher (11&ndash, 12 at.%) Ti films also showed higher density, lower surface roughness, and a finer grain structure. As a result, these films had a higher hardness compared to the sub-stoichiometric films, with hardness levels in the range of 18&ndash, 23 GPa, typical of transition metal nitrides coatings.