Based on a combined computational and experimental study, we show that besides the thermodynamically stable β-MoN_0.5 and δ₂-MoN phases, also metastable γ-MoN_x and its ordered relative γ′-MoN_x can be synthesized by physical vapor deposition. The formation of the NaCl-based γ-MoN_x phase is favored for nitrogen concentrations between 23 and 34 at.% (i.e., x = 0.30–0.53). Higher nitrogen contents (close to the 3:2 stoichiometry, hence, MoN_0.67) favor the ordering of the vacancies at the nitrogen sublattice (hence, γ′-MoN_x). The highest hardness of ∼33 GPa is obtained for single-phase cubic-structured γ-MoN_0.53 coatings, whereas the ordered γ′-MoN_0.67 coatings are slightly softer with a hardness of ∼28 GPa.

We present a combined experimental and theoretical investigation of sputter deposited thin films in the ternary system Ti1−xWxB2. Solid solutions of Ti1−xWxB2−z were prepared by physical vapor deposition (PVD) and, over the whole composition range, found to crystallize in the AlB2 structure type. The obtained films exhibit good thermal stability and high hardness, evidencing a maximum value of almost 40GPa for Ti0.67W0.33B2−z. The effect of vacancies on stabilization and mechanical properties of the AlB2 structure type is discussed, using ab initio simulations. Based on our results, we can conclude that vacancies are crucial for the phase stability of PVD deposited Ti1−xWxB2−z coatings

In this study, the effects of the microstructural properties on the deformation and damage mechanism of CrN/TiN multilayer coatings deposited on Custom 450 steel using the unbalanced reactive magnetron sputtering PVD process were studied. All coatings were fabricated with an overall thickness of 1.5 µm, but different bilayer periods (Λ). Structural and mechanical properties of coatings were investigated by XRD analysis and nanoindentation experiment, respectively. Indentation tests at three loads of 100, 300, and 450 mN were performed on the coatings’ surface and then, cross-sections of fractured imprints were analyzed with SEM and TEM. Measuring the length of the cracks induced by indentation loads and analyzing the load-displacement curves, apparent fracture energy values of multilayer coatings were calculated. We observed that multilayer systems with bilayer periods of 4.5–15 nm possess superlattice structure, which also results in higher values for Young’s modulus and hardness as well as higher fracture energy. Comparison of cross-sectional SEM and TEM observations showed that coatings with smaller bilayer periods tend to deform by shear sliding mechanism due to the existence of the long-grown columns, while short dispersed grains—growing in the coatings with a larger bilayer period—led to deformation via local grain boundary sliding and grain rotation.

Ab initio calculations show that with increasing N-vacancy content of Mo1-xAlxNy solid solutions, the cubic structure is increasingly preferred over the wurtzite-type hexagonal structure. While Mo1-xAlxN solid solutions, without N-vacancies, energetically favor the wurtzite-type structure over the whole composition range, Mo1-xAlxN0.5(1+x) and Mo1-xAlxN0.5 solid solutions energetically prefer the cubic structure up to ∼45 and 65 at.% Al at the metal sublattice.Detailed ab initio calculations in combination with detailed elemental and phase composition analyses and nanoindentation experiments of reactively sputtered Mo1-xAlxNy coatings prove the formation of face-centered cubic structures for Al-contents x ≤ 0.57. These Mo1-xAlxNy coatings exhibit an Al-dependent population of the nitrogen sublattice, following the MoN0.5–AlN quasi-binary tie line. For Al-contents x ≥ 0.79 the coatings crystallize in the wurtzite-type hexagonal phase, while in the intermediate composition range both phases, cubic and wurtzite-type hexagonal, coexist. As long as the cubic structure is maintained, the hardness increases from ∼33.0 to 38.4 GPa with increasing Al-content, but drops to ∼22 GPa for x ≥ 0.67, when the films contain hexagonal wurtzite-type phases