Sputtering-Power-Ratio Engineering of SS–Ti–N Coatings: Correlation of Composition, Structure, Morphology, and Hardness

Reactive magnetron sputtering offers an effective route for tailoring the composition and properties of hard nitride coatings through controlled adjustment of deposition parameters. In this study, stainless-steel–Ti–N (SS–Ti–N) coatings were deposited by reactive magnetron co-sputtering from stainless-steel (SS) and titanium (Ti) targets in an Ar/N2 atmosphere. The influence of the SS/Ti sputtering-power ratio was systematically investigated by maintaining the Ti target power at 170 W while reducing the SS target power from 170 to 100 and 70 W. The chemical composition, crystal structure, cross-sectional morphology, surface roughness, and hardness were evaluated using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, stylus profilometry, and micro-Knoop hardness testing, respectively. XPS revealed increases in Ti and N concentrations from 4.25 to 14.0 at.% and from 35.6 to 47.7 at.%, respectively, as the SS target power decreased. XRD revealed an fcc-based, nitrogen-rich structure with changes in lattice spacing, while SEM showed an evolution toward a more uniform and compact columnar morphology. These changes were accompanied by a decrease in surface roughness from approximately 0.012 to 0.005 µm and an increase in hardness from 2450 to 3198 kgf/mm2 (approximately 24.0 to 31.4 GPa). Among the investigated coatings, the sample deposited at an SS/Ti target-power combination of 70/170 W exhibited the highest Ti and N concentrations, the lowest surface roughness, and the highest hardness. These findings demonstrate that adjusting the relative sputtering powers provides a practical means of tailoring the composition, structure, morphology, and mechanical properties of SS–Ti–N coatings, highlighting their potential for protective surface-engineering applications.