Thermal stability of arc evaporated high aluminum-content Ti1−xAlxN thin films (original) (raw)
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Structure and thermal stability of arc evaporated (Ti0.33Al0.67)1−xSixN thin films
Thin Solid Films, 2008
Ti 0.33 Al 0.67) 1-x Si x N (0≤x≤0.29) thin solid films were deposited onto cemented carbide substrates by arc evaporation and analyzed using analytical electron microscopy, X-ray diffraction, nanoindentation, and density functional theory. As-deposited films with x≤0.02 consisted mainly of a metastable c-(Ti,Al)N solid solution for which Si serves as a veritable grain refiner. Additional Si promoted growth of a hexagonal wurtzite (Al,Ti,Si)N solid solution, which dominated at 0.02<x<0.17. For x≥0.17, the films were X-ray amorphous. Despite these widely different microstructures, all as-deposited films had nanoindentation hardness in the narrow range of 22-25 GPa. Isothermal annealing of the x=0.01 alloy film at a temperature of 900 °C, corresponding to that in turning operation, resulted in spinodal decomposition into c-AlN and TiN and precipitation of h-AlN. For x=0.09 films, annealing between 600 °C and 1000 °C yielded c-TiN precipitation from the h-(Al,Ti,Si)N-phase. Furthermore, the x=0.01 and x=0.09 films 3 exhibited substantial age hardening at 900 °C, to 34 GPa and 29 GPa due to spinodal decomposition and c-TiN precipitation, respectively. Films with a majority of c-(Ti,Al)N phase worked best in steel turning tests, while films with x>0.02 developed cracks during such operation. We propose that the cracks are due to tensile strain which is caused by a decrease in molar volume during the phase transformation from hexagonal wurtzite (Al,Ti,Si)N into cubic TiN phase, which results in degradation in machining performance.
Thin Solid Films, 1998
. The microstructure of a series of Ti Al N films prepared by Chemical Vapour Deposition CVD is investigated using Scanning 1yx x Ž . Ž . Ž . Electron Microscopy SEM , Transmission Electron Microscopy TEM and Electron Energy Loss Spectroscopy imaging EELS . A comparison is made with the microstructure of a film obtained using a magnetron sputtering method. CVD films were prepared with substrate temperatures ranging from 400 to 4508C. Plan-view and cross-sectional observations show that they are made of nanocrystallites, a majority of these being organised in columnar clusters. The sharpest electron diffraction patterns obtained from the films are indexed in terms of the fcc TiN structure-type with a lattice parameter a, decreasing slightly with increasing aluminum content. In the film deposited by magnetron sputtering the main structure is fcc TiN-type with a lattice parameter of 4.17 A and the observed grain size is 300 nm, a value much larger than the grain size obtained from CVD films, although the deposition was done at room temperature. The EELS imaging technique also shows that throughout the series, Ti, Al and N are homogeneously distributed. q 1998 Elsevier Science S.A.
Increased thermal stability of Ti–Al–N thin films by Ta alloying
Surface and Coatings Technology, 2012
To increase the thermal stability of protective coatings has always been a major topic for application oriented materials development. Here, we study the impact of Ta on the thermal stability of magnetron sputtered Ti 1−x Al x N thin films using a combined ab initio and experimental approach. With increasing Ta content in Ti 1−x−y Al x Ta y N, a decreasing energy of formation, as well as an increasing interaction of the transition metal d-states go along with an increase in cohesive energy, which point toward a higher stability of the quaternary system. The ab initio predicted increasing bonding strength of Ti 1−x−y Al x Ta y N with increasing Ta content was corroborated by structural and mechanical investigations of Ti 1−x−y Al x Ta y N thin films with y = 0, 0.03, 0.05, and 0.1, respectively. With increasing Ta content, a hardness increase of 25%, from 30 GPa to~40 GPa, can be observed after deposition. Annealing experiments in vacuum show that the decomposition process of the supersaturated solid solution towards their stable constituents c-Ti 1-z Ta z N (with z = y/(1− x)) and hexagonal (wurtzite structure, w) w-AlN, is effectively retarded from~900 to~1200°C with increasing Ta content. The involved decomposition into c-Ti-Ta-rich and c-Al-rich domains results in hardness maxima of~38 to~42 GPa for y =0 and 0.1, respectively. Oxidation experiments for 20 h at 850 and 950°C yielded fully oxidized Ta-free coatings, whereas the addition of only 3 at.% Ta to the metal sublattice results in the form of a layered oxide scale and remaining unoxidized nitride layer thicknesses of~95 and~87% (with respect to the as deposited films), respectively.
Significance of Al on the morphological and optical properties of Ti1−xAlxN thin films
Materials Chemistry and Physics, 2011
TiN and Ti 1−x Al x N thin films with different aluminum concentrations (x = 0.35, 0.40, 0.55, 0.64 and 0.81) were synthesized by reactive magnetron co-sputtering technique. The structure, surface morphology and optical properties were examined using Grazing Incidence X-ray Diffraction (GIXRD), Atomic Force Microscopy (AFM), Raman spectroscopy and spectroscopic ellipsometry, respectively. The structure of the films were found to be of rocksalt type (NaCl) for x = 0.0-0.64 and X-ray amorphous for x = 0.81. AFM topographies show continuous mound like structure for the films of x between 0.0 and 0.64, whereas the film with x = 0.81 showed smooth surface with fine grains. Micro-Raman spectroscopic studies indicate structural phase separation of AlN from TiAlN matrix for x > 0.40. Ti 1−x Al x N has the tendency for decomposition with the increase of Al concentration whereas c-TiN and hcp-AlN are stable mostly. The optical studies carried out by spectroscopic ellipsometry measurements showed a change from metallic to insulating behavior with the increase in x. These films are found to be an insulator beyond x = 0.81.
X-ray diffraction on nanocrystalline Ti1−xAlxN thin films
Journal of Alloys and Compounds, 2004
Microstructure of titanium aluminium nitride thin films deposited using arc evaporation was investigated for different aluminium contents. From Ti 0.96 Al 0.04 N to Ti 0.38 Al 0.62 N, the dominant phase in the coatings was the fcc Ti 1−x Al x N. In this concentration range, the compressive residual stress as well as the hardness of the coatings increased with increasing aluminium contents. Crystallites of Ti 1−x Al x N were strongly textured; the preferred orientation was found to be related to the deposition geometry, not to the composition of the coatings. Concurrently, preferred orientation of crystallites was found to be a very important parameter influencing the crystal anisotropy of lattice deformation and the coherence of neighbouring crystallites. At higher aluminium contents (x > 0.8), the dominant phase was the hexagonal AlN; the hardness of the films decreased. (D. Rafaja). structure: scatter of lattice parameters, very high residual stress and very high microstrain. 0925-8388/$ -see front matter
Acta Materialia, 2002
We report the stress relaxation behavior of arc-evaporated TiC x N 1Ϫx thin films during isothermal annealing between 350 and 900°C. Films with x ϭ 0, 0.15, and 0.45, each having an initial compressive intrinsic stress s int ϭ Ϫ 5.4GPa, were deposited by varying the substrate bias V s and the gas composition. Annealing above the deposition temperature leads to a steep decrease in the magnitude of s int to a saturation stress value, which is a function of the annealing temperature. The corresponding apparent activation energies for stress relaxation are E a ϭ 2.4, 2.9, and 3.1eV, for x ϭ 0, 0.15, and 0.45, respectively. TiC 0.45 N 0.55 films with a lower initial stress s int ϭ Ϫ 3GPa, obtained using a high substrate bias, show a higher activation energy E a ϭ 4.2eV. In all the films, stress relaxation is accompanied by a decrease in defect density indicated by the decreased width of X-ray diffraction peaks and decreased strain contrast in transmission electron micrographs. Correlation of these results with film hardness and microstructure measurements indicates that the stress relaxation is a result of point-defect annihilation taking place both during shortlived metal-ion surface collision cascades during deposition, and during post-deposition annealing by thermally activated processes. The difference in E a for the films of the same composition deposited at different V s suggests the existence of different types of point-defect configurations and recombination mechanisms.
Surface and Coatings Technology, 2005
Ti 1Àx Si x N (0 x 0.14) thin solid films were deposited onto cemented carbide (WC-Co) substrates by arc evaporation. X-ray diffraction and transmission electron microscopy showed that all films were of NaCl-structure type phase. The as-deposited films exhibited a competitive columnar growth mode where the structure transits to a feather-like nanostructure with increasing Si content. Films with 0 x 0.01 had a b111À crystallographic preferred orientation which changed to an exclusive b200À texture for 0.05 x 0.14. X-ray photoelectron spectroscopy revealed the presence of SiN bonding, but no amorphous Si 3 N 4. Band structure calculations performed using a full potential linear muffin tin orbital method showed that for a given NaCl-structure Ti 1Àx Si x N solid solution, a phase separation into cubic SiN and TiN is energetically favorable. The microstructure was maintained for the Ti 0.86 Si 0.14 N film annealed at 900-C, while recrystallization in the cubic state took place at 1100-C annealing during 2 h. The Si content influenced the film hardness close to linearly, by combination of solid-solution hardening in the cubic state and defect hardening. For x = 0 and x = 0.14, nanoindentation gave a hardness of 31.3 T 1.3 GPa and 44.7 T 1.9 GPa, respectively. The hardness was retained after annealing at 900-C, while it decreased to below 30 GPa for 1100-C following recrystallization and W and Co interdiffusion.
Research Journal of Pharmaceutical, Biological and Chemical Sciences
The temperature conditions for different formation stages of nanostructured and polycrystal Ti 1-х Al x N thin films have been identified for the first time, using cathodic arc evaporation. A three-axis structural zone model has been developed to identify structural zones of Ti 1-х Al x N thin films. This model, combined with chemical analysis, has been used to establish a pattern for 0 ≤ х ≤ 0.4 in Ti 1-х Al x Nthin films with reference to the formation process and temperature conditions. Nanostructured Ti 0,6 Al 0,4 N films formed at the maximum film heating rate and at the optimum gas mixture pressure have the highest aluminum content С Al =x= 28.7 at.% and the film composition approaches the stoichiometric one. If the С Al is higher than 26.5 at.% and the С Al /C Ti =x/1-x is higher than 0.6, the size of the coherent scattering region (CSR) declines sharply to 10 nm. The degree of texturization of the Ti 1-х Al х N thin films steadily increases with the growth of the С Al and С Al /C Ti . An improvement in physical and mechanical properties of Ti 1-х Al x N thin films can be achieved by bringing the С Al to ≥ 26.5 at.%, by bringing the С Al /C Ti to ≥ 0.6, by reducing the CSR size to 10 nm, by ordering the microstructure, and by increasing the degree of texturization of Ti 1-х Al х N thin films to 0.8. The Ti 1-х Al x N thin films also exhibit excellent sliding wear resistance and a low friction coefficient due to maximum full free energy of 71.3 eV and Al 2 O 3 layer which diminishes O 2 diffusion into Ti 1-х Al х N thin film and preserves its microhardness at high temperatures. If the С Al and С Al /C Ti conditions are not met, the influence of Ti 1-х Al х N films on the properties is significant.
2 A Practical Application of X-Ray Spectroscopy in Ti-AlN and Cr-AlN Thin Films
2017
Binary and ternary transition metal nitrides coatings have been used in numerous applications to increase the hardness and improve the wear and corrosion resistance of structural materials, as well as in various high-tech areas, where their functional rather than tribological and mechanical properties are of prime importance (Münz, 1986; Chen & Duh, 1991; PalDey & Deevi, 2003; Ipaz et al., 2010). Up to now, Ti-Al-N and Cr-Al-N films have been synthesized by a variety of deposition techniques including cathodic arc evaporation (Cheng et al., 2001), ion plating (Setsuhara et al., 1997), chemical vapor deposition (CVD) or plasma-enhanced CVD (Shieh & Hon, 2001) and d.c. / r.f. reactive magnetron sputtering (Musil & Hruby, 2000; Sanchéz et al., 2010). Performance of these coatings is equally dependent on their chemical composition and long-range crystalline structure, as well as on the nature and amount of impurities and intergranular interactions. Significant improvement in the mechani...
Structure and mechanical properties of arc evaporated Ti–Al–O–N thin films
Surface and Coatings Technology, 2007
The structure, mechanical properties, and machining performance of arc evaporated Ti-Al-ON coatings have been investigated for an Al 0.66 Ti 0.34 target composition and O 2 /(O 2 +N 2) gas flow-ratio varied between 0 to 24%. The coating structure was analysed using SEM, EDX, XRD, XPS, TEM, and STEM. Mechanical properties were analysed using nanoindentation and the deformation behaviour was analysed by probing the nanoindentation craters. The coatings performances in cutting tests were evaluated in a turning application in low carbon steel (DIN Ck45). It is shown that the addition of oxygen into the arc deposition process leads to the formation of a dual layer structure. It consists of an initial cubic NaCl-structure solid solution phase formed closest to the substrate, containing up to 35 at.% oxygen (O/O+N), followed by steady-state growth of a nanocomposite compound layer comprised of Al 2 O 3 , AlN, TiN, and Ti(O,N). The addition of oxygen increases the ductility of the coatings, which improves the performances in cutting tests. At high levels of oxygen, (N 13 at.%), however, the performance is dramatically reduced as a result of increased crater wear.