Effect of Internal Interfaces on Hardness and Thermal Stability of Nanocrystalline Ti0.5Al0.5N Coatings

Abstract

The effect of microstructure on the thermal stability and hardness of the cathodic arc evaporated Ti 0.5 Al 0.5 N coatings was investigated with the aid of the in-situ high-temperature X-ray diffraction experiments, which were accompanied by high-resolution transmission electron microscopy (HRTEM) and nanoindentation measurements. The microstructure of the coatings was modified through the choice of the bias voltage in the deposition process. It was found that the bias voltage affects strongly the uniformity of the local distribution of titanium and aluminum in the coatings. The nonuniform distribution of the elements contributes to the formation of lattice strains at the crystallite and phase boundaries. The lattice strains at the crystallite boundaries increase the hardness of the coatings; the lattice strains at the phase boundaries improve their thermal stability. A certain nonuniformity of the distribution of the metallic species in the coatings is regarded as advantageous. However, a great nonuniformity in the distribution of the metallic species accelerates the degradation of the coatings at high temperatures. As a measure for the nonuniformity of the distribution of the atomic species in the as-deposited (Ti, Al) N samples, the stress-free lattice parameter of fcc-(Ti, Al) N is suggested.

Face Centred Cubic Multi-Component Equiatomic Solid Solutions in the Au-Cu-Ni-Pd-Pt System

“…This slope, is governed by segregations and also influenced by dislocations which was also observed for other systems that obey Vegard's rule of mixture [28][29][30]. Since, thanks to the EDX measurements, the effect of the lattice parameter variation can be separated from the microstrain.…”

Strain evolution during spinodal decomposition of TiAlN thin films

“…9. Formation of tensile strains during decomposition has also been observed experimentally for Ti 0.50 Al 0.50 N thin films [27]. As was discussed in the previous section, the decomposition is expected to begin already before 950 °C for [35] observed that for a two-phase mixture of hexagonal and cubic phases in high Al content TiAlN the lattice strains were increased compared to a single phase film.…”

“…The presence of two or more phases can result in epitaxial misfit strains [25]. Further, phase transformations in the film after growth can cause additional strains [18,26,27].…”

Thermal and mechanical stability of wurtzite-ZrAlN/cubic-TiN and wurtzite-ZrAlN/cubic-ZrN multilayers

“…The archetype for this approach is the metastable cubic (c-) Ti 1-x Al x N solid solution, which forms nm-sized domains by spinodal decomposition when exposed to high temperatures (around 900 °C) [5][6][7][8]. At even higher temperatures this alloy further decomposes into its thermodynamically stable phases c-TiN and wurtzite (w-) AlN [9] that deteriorates the mechanical properties [10,11]. The related Zr 1-x Al x N alloys display characteristics similar to Ti 1-x Al x N with a miscibility gap for cubic solid solutions and a higher driving force for decomposition compared to Ti 1-x Al x N [12,13] resulting in promising mechanical properties [14][15][16][17][18] at high temperature.…”