Reactive Nitrogen Atmosphere Research Articles

In situ nitriding of Fe2VAl during laser surface remelting to manipulate microstructure and crystalline defects

Tailoring the physical properties of complex materials for targeted applications requires optimizing the microstructure and crystalline defects that influence electrical and thermal transport and mechanical properties. Laser surface remelting can be used to modify the subsurface microstructure of bulk materials and hence manipulate their properties locally. Here, we introduce an approach to perform remelting in a reactive nitrogen atmosphere to form nitrides and induce segregation of nitrogen to structural defects. These defects arise from the fast solidification of the full-Heusler ${\mathrm{Fe}}_{2}\mathrm{VAl}$ compound that is a promising thermoelectric material. Advanced scanning electron microscopy, including electron channeling contrast imaging and three-dimensional electron backscatter diffraction, is complemented by atom probe tomography to study the distribution of crystalline defects and their local chemical composition. We reveal a high density of dislocations, which are stable due to their character as geometrically necessary dislocations. At these dislocations and low-angle grain boundaries, we observe segregation of nitrogen and vanadium, which can be enhanced by repeated remelting in nitrogen atmosphere. We propose that this approach can be generalized to other additive manufacturing processes to promote local segregation and precipitation states, thereby manipulating physical properties.

PVD hard coatings on ceramic tiles for aesthetic applications: surface characterisation and corrosion properties

The development of innovative ceramic tiles looks for materials with improved mechanical and tribological properties as well as a higher corrosion resistance (high relative humidity, daily watering, household chemical cleaners). In addition, a greater durability leads to lower environmental impact. Along with their improved functionality and recyclability, ceramic tiles should also provide aesthetic properties. Ceramic tiles can be treated to modify the physico-chemical properties of the surface by metal coatings or metallic compounds, also providing an attractive metallic sheen appearance. In the present paper, titanium nitride (TiN) and zirconium nitride (ZrN) coatings were deposited on glazed porcelain stoneware by an industrial PVD multicathode arc deposition system under a reactive nitrogen atmosphere. After the process, the tiles showed a gold-like colour, a smooth surface and a coating thickness between 0.7 and 1.6 μm. The coating composition, scratch resistance and corrosion behaviour have been evaluated. It can be concluded that both coatings are suitable for use in domestic environments due to their stability and resistance to aggressive conditions. Few references have been found regarding these coatings on ceramic tiles for domestic and industrial applications, but it has been proved that they bring added value to traditional ceramics, giving new functional properties of ceramics both decorative and highly corrosion and mechanical resistance.

Microstructure evolution and mechanical properties of laser additive manufactured Ti6Al4V alloy under nitrogen-argon reactive atmosphere

It is known that the reactive nitrogen atmosphere can effectively modulate the microstructure of laser powder bed fusion (L-PBF) of Ti6Al4V alloys. In the present work, high nitrogen contents of 15 and 25 vol% were applied in argon atmospheres to investigate the influence on microstructure and mechanical performances. The enhanced nitrogen solid solution was achieved with nitrogen content ranging 374 ppm and 456 ppm (parts per million) in the Ti6Al4V alloys, respectively. Besides, the EBSD (electron back-scattered diffraction) characterization shows the significant refinement of acicular martensite α′ and the EBSD phase reconstruction shows the interrupting epitaxial growth of the β phase with the increasing nitrogen content in the atmosphere. The KAM (kernel average misorientation) diagrams with an increasingly higher value indicate an increased micro-strain and dislocation density at higher nitrogen content in the atmosphere. Meanwhile, the high magnification TEM further confirms the martensite α’ refinement and also the formation of β lamella at 25 vol% nitrogen content in L-PBF atmosphere. Such microstructure evolution can be mainly attributed to the more severe thermal cycling with a higher thermal gradient and cooling rate under the atmosphere with higher nitrogen content. By applying the 25 vol% nitrogen in the atmosphere, the L-PBF Ti6Al4V alloys exhibit a significant increase in maximum compressive strength of ∼1885 MPa and maximum compressive strain of ∼10%, respectively. The underlying strengthening mechanism can be attributed to the refinement of martensite structure, solid solution, and higher dislocation density. The present work shows that the atmosphere can effectively modulate the microstructure and improve the mechanical property of L-PBF alloys.

Effect of Sputtering Atmosphere on ZnSnN2 Thin Films Electrical and Optoelectronic Properties

ZnSnN2 is a member of ternary Zn-IV-N2 semiconductors, where IV = Si, Ge or Sn. According to theoretical calculations and preliminary experimental results, Zn-IV-N2 semiconductor materials afford same bandgap range than III-nitride semiconductors. It is also expected similar electronic and optical properties as for InGaN, for example, direct bandgaps and large optical absorption coefficients [1][2]. Based on first-principles calculations, ZnSnN2 becomes a promising material for photovoltaic. Exhibiting a bandgap value around 1.7 - 2 eV, it can provide an interesting alternative furnishing an inorganic thin film solution for tandem cell over silicon [3]. The most stable wurtzite-derived structure of bulk ZnSnN2 was given to be the orthorhombic Pna21 phase by calculating the total energy per unit cell, band structure and electronic density of states [4]. ZnSnN2 can be synthesized from various methods, in which sputtering technique tends to dominate. The primary advantages of using sputtering are high deposition rates, application for most materials, high-purity and adhesive films, ability to coat heat-sensitive substrates (glass substrates, plastic substrates) and automation capabilities [5]. It provides, moreover, a realistic way of integration with Si based bottom cells. By changing the experiment conditions, band gap can expand to 2 eV [6], n-type carrier concentration obtained 7.01x1017cm3 and high mobility receive up to 15.5 cm2/V.s [7].In this work, ZnSnN2 thin films were produced on glass substrates by co-sputtering Zn and Sn targets at room temperature in a reactive atmosphere of argon, nitrogen and hydrogen. By changing the composition of this atmosphere, the optical and electrical properties of material are changed. The morphology and crystal structure were investigated by using SEM, AFM and X-ray diffraction. The optical band gap ranges from 1.8eV to 2.5 eV and was deduced from UV-VIS spectroscopy. The n-type carrier concentration was measured between 2.5e17 to 2.4e20 cm-3, and the highest carried mobility is 2.0 cm2/V.s. First photoconductive samples were fabricated and tested under solar simulator. Measurement gave a photocurrent value of 148mA/cm2. These results are promising ones for the potential application of ZnSnN2 material as a photovoltaic absorber.

Effect of Sputtering Atmosphere on ZnSnN2 Thin Films Electrical and Optoelectronic Properties

ZnSnN2 thin films were produced on glass substrates by co-sputtering Zn and Sn targets at room temperature in a reactive atmosphere of argon, nitrogen and hydrogen. By changing the composition of this atmosphere, the optical and electrical properties of material are changed. The morphology and crystal structure were investigated by using SEM, AFM and X-ray diffraction. The optical band gap ranges from 1.80 eV to 2.13 eV and was deduced from UV-VIS spectroscopy. The n-type carrier concentration was measured between 2.5 x 1017 and 1.0 x 1020 cm-3 and the highest carrier mobility is 2.0 cm2V-1s-1. First photoconductive samples were fabricated and tested under solar simulator. Measurement gave a photocurrent value of 150 mA/cm2. These results are promising ones for the potential application of ZnSnN2 material as a photovoltaic absorber.

X-ray photoelectron spectroscopy and rotating disk electrode measurements of smooth sputtered Fe-N-C films

Electrocatalysts for the oxygen reduction reaction (ORR) based on complexes of iron and nitrogen in a carbon matrix (Fe-N-C) are a promising alternative to platinum group metal (PGM) based catalysts in polymer electrolyte membrane (PEM) fuel cells. Further improvements of Fe-N-C catalysts would benefit from model thin film studies of activity and stability of catalytic sites, but synthesis of Fe-N-C model thin films is challenging. Here we report on synthesis and characterization of Fe-N-C thin films produced by co-sputtering iron and carbon in a reactive nitrogen atmosphere onto removable glassy carbon rotating disk electrode (RDE) tips. Scanning electron microscopy (SEM) measurements indicate that the Fe-N-C films deposited at high temperature are smoother than the films annealed at high temperature. Electrocatalytic activity measured on the thin Fe-N-C films is greater for both high-temperature samples than for the room-temperature sample. From the analysis of X-ray photoelectron spectroscopy (XPS) data, exposure of the films to high temperatures results in increased graphitization of the carbon within the Fe-N-C films, and increased relative amount of graphitic and hydrogenated nitrogen species. Overall, the results of this study demonstrate the feasibility of a thin film model system approach for studying active sites in PGM-free catalysts.

Concentrated solar energy for in-situ elaboration of wear-resistant composite layers. Part II: Tungsten carbide surface enrichment of common steels

The present work constitutes the second part of a study concerning the application of Concentrated Solar Energy (CSE) for the in-situ elaboration of carbide-reinforced surface layers onto common steels, employing WC as a model system. As in the first part that involved titanium and chromium carbides as reinforcing compounds, “solar hardfacing” experiments were carried out in the solar furnace SF40, at the installations of Plataforma Solar de Almería (Spain). Parametric studies performed were targeted to clarify the effects of solar irradiation time and inert or reactive processing atmosphere on the structural integrity, microstructure, carbide dispersion and hardness of the surface layers obtained. The results were used, on the one hand to identify conditions for the elaboration of wear resistant surface layers and on the other hand to elucidate the fundamental mechanisms governing the dispersion of WC particles in a liquid ferrous matrix that is, subsequently, re-solidified. In contrast to the TiC particles, WC ones are subjected to liquid metal attack transforming progressively to mixed FeW carbides, as determined by scanning electron microscopy and X-ray diffraction. Under inert atmosphere, solar processing beyond a threshold time period decreases the in-depth homogeneity of the carbides dispersion and increases the extent of the attack, deteriorating hence the composite character of the layer obtained. Reactive nitrogen atmosphere mitigates the negative effects of prolonged exposure, allowing the elaboration of thick hardfacing layers. Finally, dry sliding friction tests allowed defining the friction coefficient and specific wear rate, as well as the synergy of the wear micro-mechanisms involved. These results complemented with the respective ones for titanium and chromium carbide-based hardfacing layers, provide a first framework for the rational and optimized elaboration of wear resistant carbide-based surface layers using concentrated solar energy.

Effect of Target Composition and Sputtering Deposition Parameters on the Functional Properties of Nitrogenized Ag-Permalloy Flexible Thin Films Deposited on Polymer Substrates.

We report the first results of functional properties of nitrogenized silver-permalloy thin films deposited on polyethylene terephthalic ester {PETE (C10H8O4)n} flexible substrates by magnetron sputtering. These new soft magnetic thin films have magnetization that is comparable to pure Ni81Fe19 permalloy films. Two target compositions (Ni76Fe19Ag5 and Ni72Fe18Ag10) were used to study the effect of compositional variation and sputtering parameters, including nitrogen flow rate on the phase evolution and surface properties. Aggregate flow rate and total pressure of Ar+N2 mixture was 60 sccm and 0.55 Pa, respectively. The distance between target and the substrate was kept at 100 mm, while using sputtering power from 100–130 W. Average film deposition rate was confirmed at around 2.05 nm/min for argon atmosphere and was reduced to 1.8 nm/min in reactive nitrogen atmosphere. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, vibrating sample magnetometer, and contact angle measurements were used to characterize the functional properties. Nano sized character of films was confirmed by XRD and SEM. It is found that the grain size was reduced by the formation of nitride phase, which in turns enhanced the magnetization and lowers the coercivity. Magnetic field coupling efficiency limit was determined from 1.6–2 GHz frequency limit. The results of comparable magnetic performance, lowest magnetic loss, and highest surface free energy, confirming that 15 sccm nitrogen flow rate at 115 W is optimal for producing Ag-doped permalloy flexible thin films having excellent magnetic field coupling efficiency.

Structure and wear characteristics of TiCN nanocomposite coatings fabricated by reactive plasma spraying

In this present work, titanium carbonitride (TiCN) coatings were successfully fabricated by reactive plasma spraying from agglomerated Ti-graphite feedstock under reactive nitrogen atmosphere. The microstructure and morphology were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution TEM. The mechanical and tribological performances were measured using a nanoindentation tester, tensile tester and block-on-ring tribometer. Results show that typical equiaxed grains with size about 40–90 nm is obtained. The as-sprayed coating consists of nano scaled TiC0.7N0.3, TiC0.3N0.7 and Ti2O crystalline phases with some amorphous phases (graphite and CNx), which would influence the mechanical and tribological properties of coating directly. When compared with TiN coating, TiCN coating exhibits a higher hardness and higher H/E and H3/E2 ratios with values of 27.1 GP, 0.1 and 0.3 GPa, respectively. This could benefit TiCN coating possessing high deformation resistance and large elastic recoverability to reduce the damage by impact and wear. Furthermore, the main wear mechanism of TiCN coating is tribo-oxidation wear and abrasive wear.

Effect of bias voltage and nitrogen pressure on the structure and properties of vacuum-arc (Mo + Ti6%Si)N coatings

Effect of deposition conditions in reactive nitrogen atmosphere on the growth morphology, phase composition, structure, and mechanical characteristics (microhardness) of vacuum-arc multilayer coatings obtained using evaporation of the (Ti6%Si) and Mo cathodes is studied with the aid of raster electron microscopy, energy-dispersive elemental microanalysis, and microindentation. It is demonstrated that nitrogen atoms are redistributed to the region of the strongest nitride-forming element (Ti) in relatively thin layers (about 7 nm) consisting of substances with substantially different heats of formation (−336 kJ/mol for TiN and −34 kJ/mol for MoN). Such a process leads to lamination with the formation of nitride TiN and metal Mo (weaker nitride-forming element). Nitrogen–metal bonds are saturated in the layers of strong nitrideforming elements Ti(Si) when the nitrogen pressure increases from 6 × 10–4 to 5 × 10–3 Torr in the condensation procedure. Thus, the compound is filled with nitrogen to the stoichiometric composition and, then, the second system of layers based on molybdenum is saturated with nitrogen with the formation of the γ-Mo2N phase. An increase in bias potential U SP from–100 to–200 V stimulates mixing in thin layers with the formation of the (Ti, Si, Mo)N solid solution and leads to a decrease in microhardness from 37 to 32 GPa.

Influence of the high-temperature annealing on the structure and mechanical properties of vacuum–arc coatings from Mo/(Ti + 6 wt % Si)N

Scanning electron microscopy with energy dispersive element microanalysis, X-ray structural analysis, and microindentation were used to study the effect of the deposition conditions in a reactive nitrogen atmosphere on the growth morphology, phase composition, structure, and microhardness of vacuum–arc multilayer coatings produced by the evaporation of cathodes from Mo and (Ti + 6 wt % Si) both after their deposition and after high-temperature annealing. It has been established that the use of the composite cathode of Ti and Si allows the formation of the structure state inclined to ordering to form a two-phase compound from TiN and Ti5Si3 at high-temperature annealing. In this case the coating hardness increases to a value higher than 45 GPa.

Evolution of physical properties in hafnium carbonitride thin films

Hafnium carbonitride coatings were deposited onto silicon substrates by reactive r.f. magnetron co-sputtering from hafnium and carbon targets in a reactive nitrogen atmosphere, varying applied negative bias voltages (0, −50, −100, and −150 V). The effect of the applied bias voltage on the crystalline structure, chemical composition, and mechanical properties was observed via X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and nanoindentation techniques. The results show that the samples present constant stoichiometric ratio, Hf/(C+N), exhibiting improved mechanical properties by increasing negative bias voltage from 17 to 32 GPa for the hardness and from 200 to 280 GPa for elastic modulus. Therefore, the HfCN coatings can be used as future hard coating materials.

Cubic AlN thin film formation on quartz substrate by pulse laser deposition**Project supported by the Yunnan Provincial Natural of Science Foundation of China (No. KKSY201251089).

Cubic AlN thin films were obtained on quartz substrate by pulse laser deposition in a nitrogen reactive atmosphere. A Nd-YAG laser with a wavelength of 1064 nm was used as the laser source. In order to study the influence of the process parameters on the deposited AlN film, the experiments were performed at various technique parameters of laser energy density from 70 to 260 J/cm2, substrate temperature from room temperature to 800 °C and nitrogen pressure from 0.1 to 50 Pa. X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy were applied to characterize the structure and surface morphology of the deposited AlN films. It was found that the structure of AlN films deposited in a vacuum is rocksalt under the condition of substrate temperature 600-800 °C, nitrogen pressure 10-0.1 Pa and a moderate laser energy density (190 J/cm2). The high quality AlN film exhibited good optical property.

Characterization of Nanostructured and Conventional TiAlN Coatings Deposited on AISI-304 Boiler Steel

In the manuscript conventional and nanostructured nitrided coatings developed to increase hardness and to improve the wear, erosion and corrosion resistance of structural materials. Three coatings of TiAlN were deposited on AISI-304, out of which two were thin nanocoatings at different temperatures of 500°C and 200°C are developed by Oerlikon Balzer’s rapid coating system machine under a reactive nitrogen atmosphere. One conventional coating TiAl was deposited by Plasma spraying method which was post nitrided. Then the coated samples were characterized with relative to coating thickness, microhardness, porosity and structure. The XRD and SEM/EDAX techniques have been used to identify various phases formed after coating on the surface of steel.The microhardness of conventional TiAlN coating was found to be of the order of 900-950 Hv. The grain size for nanostructured TiAlN coatings deposited at 500°C and 200°C are 15nm and 14nm respectively as calculated by Sherrer’s formula from XRD plot.

Influence of the negative R.F. bias voltage on the structural, mechanical and electrical properties of Hf–C–N coatings

Abstract In this work Hf–C–N coatings were deposited on silicon substrates by reactive R.F. magnetron co-sputtering from two hafnium and carbon targets in a reactive nitrogen atmosphere at various negative bias voltages from 0 to 150 V. The effect of the bias voltage on the chemical composition, crystalline structure and mechanical properties was studied by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD) and nanoindentation. The results show that the obtained films have a Hf /( C + N ) ratio of around 1 and present an evolution with the bias voltage from a quasi-amorphous structure, with a low hardness (6 GPa) to crystalline Hf 2 CN films with a high hardness (23 GPa) and electrical resistivity values in the order of 10 4 Ω·cm − 1 . This study shows the potential for hard and electrically conductive Hf–C–N films in industrial applications.

Polymer‐Derived Ceramic Coil Springs

Polymer‐derived ceramic coil springs were manufactured by thermoplastic coiling of extruded filaments. Feedstocks for extrusion were processed from polymethylsilsesquioxane loaded with 34 vol% FeSiCr (reactive filler) and 16 vol% Si3N4 (inert filler). The pyrolytic conversion into a composite residue, the surface reactions, and the mechanical properties were analyzed. Annealing the extruded spring preforms in a reactive nitrogen atmosphere at 1300 °C resulted in the formation of a surface reaction zone with a thickness <10 μm where nitridation reaction products are likely to heal cracks and pores. The as‐pyrolyzed ceramic springs (without surface machining) were loaded in compression. Ceramic coil springs with a filament diameter of 2.5 mm were characterized by a spring constant of 14.3 N mm−1 and attained a fracture stress of 187 ± 40 MPa.

Lithium Phosphorous Sulfurous Oxynitride (LiPSON) as a New Solid Electrolyte Material for Application in Thin-Film Batteries and Electrochromic Devices

Compared to lithium ion batteries of current generation which contain liquid or gel-electrolytes with aprotic solvents, all-solid-state batteries promise long lifetime, high volumetric energy density and inherent safety. Current battery research therefore focuses on the search for stable and incombustible inorganic solid electrolytes with high lithium ion conductivity, negligible electronic conductivity and chemical stability in contact with the electrodes – particularly towards the metallic Li anode. For the application in thin-film batteries glassy lithium phosphorous oxynitride electrolyte (LiPON) has become the state-of-the-art material due to its superior chemical stability. Commercial cells comprising LiPON are already available. Being an insulator with a high optical bandgap, LiPON may be also well suited as electrolyte in electrochromic thin film devices.However, LiPON has a relatively poor ionic conductivity (< 1 x 10-6 S cm-1) and needs to be applied as a very thin film in order to obtain sufficient current densities in a cell rendering pin-hole free large-area deposition a major technological challenge. New materials with higher conductivities would be highly desirable.Here, we report for the first time on the successful deposition of lithium phosphorous sulfurous oxynitride (LiPSON) thin films by RF magnetron sputtering from a mixed Li3PO4 and Li2SO4 target in reactive nitrogen atmosphere. The electrical properties (ionic and electronic partial conductivities) of the films have been characterized by electrochemical impedance spectroscopy (EIS) and DC polarization techniques. Ionic conductivities as high as 6 x 10-6 S cm-1 (Ea= 0.47 eV) are achieved. Moreover, we succeeded also in preparing pure LiPON films with extraordinary high ionic conductivities and high deposition rates. Our detailed analysis of the films includes the characterization of compositions by energy-dispersive X-ray spectroscopy (EDX) and by inductively coupled plasma optical emission spectrometry (ICP-OES) as well as of chemical properties by photoelectron spectroscopy (XPS). In addition, we characterized the optical properties of the films by UV-VIS spectroscopy.Finally, we will present first results of the electrical properties of cathode/LiPSON half-cells.

High Temperature Erosion Performance of Nanostructured and Conventional TiAlN Coatings on AISI-304 Boiler Steel Substrate

According to modern design philosophy better overall performance can be obtained with the modification of the surface structure and their properties without damaging underlying bulk material or substrate. The surface engineering can be classified in two broad classes: surface modification and surface coating. In the present research TiAlN coating was deposited on AISI-304 grade boiler steel using three different techniques, out of which two were thin nano coatings deposited at different temperatures of 500 and 200 °C developed by Oerlikon Balzers rapid coating system machine under a reactive nitrogen atmosphere. One conventional coating of TiAlN was deposited by plasma spraying method. The coated samples were characterized relative to their coating thickness, microhardness, porosity and micro structure. The optical microscopy, the X-ray diffraction analysis and field emission scanning electron microscope (FESEM with EDAX attachment) analysis have been used to identify various phases formed after coating deposition on the surface of AISI-304 grade boiler steel. The erosion studies were conducted on uncoated as well as coated specimens in simulated coal fired boiler environment using an air jet erosion test rig at various impingement angles of 30°, 60° and 90°. The alumina particles of average size of 50 µm were used as erodent at a velocity of 35 m/s. The eroded samples were analysed with SEM/EDAX and optical profilometer. The main objective of this research work was to increase the life of boiler tubes by using nanostructured and conventional TiAlN coatings and at the same time to compare the performance of coatings with respect to bare AISI-304 grade boiler steel. The nanostructured TiAlN coatings has shown minimum erosion rate as compared to conventional TiAlN coating and uncoated AISI-304 grade boiler steel. Maximum erosion was observed at an angle of 30° as compared to 60° and 90° indicative ductile behaviour.

Nitrogen-doped and gold-loaded TiO2 photocatalysts synthesized by sequential reactive pulsed laser deposition

Nitrogen-doped titanium oxide thin films covered by gold metal nanoparticles were grown on (001) SiO2 quartz substrates by pulsed laser deposition. A KrF* excimer laser source (λ = 248 nm, τFWHM ≤ 25 ns, ν = 10 Hz) was used for the irradiation of TiO2 and gold metal targets. The experiments were performed in controlled reactive oxygen or nitrogen atmosphere. The layers were grown for photocatalytic applications. Evaluation of photocatalytic activity was performed by photodegradation of methyl orange under near-UV light irradiation. Our results show that nitrogen doping and addition of gold nanoparticles have complementary effects, photoactivity being significantly improved as compared to that of pure titanium oxide.

Effect of bias voltage on microstructure and mechanical properties of arc evaporated (Ti, Al)N hard coatings

In the present study, authors report on the effect that substrate bias voltage has on the microstructure and mechanical properties of (Ti, Al)N hard coatings deposited with cathodic arc evaporation (CAE) technique. The coatings were deposited from a Ti 0· 5Al 0· 5 powder metallurgical target in a reactive nitrogen atmosphere at three different bias voltages: U B = − 25, −50 and −100 V. The coatings were characterized in terms of compositional, microstructural and mechanical properties. Microstructure of the coatings was investigated with the aid of X-ray diffraction in glancing angle mode, which revealed information on phase composition, crystallite size, stress-free lattice parameter and residual stress. Mechanical properties were deduced from nano-indentation measurements. The residual stress in all the coatings was compressive and increased with increasing bias voltage in a manner similar to that reported in literature for Ti–Al–N coatings deposited with CAE. The bias voltage was also found to significantly influence the phase composition and crystallite size. At −25 V bias voltage the coating was found in single phase fcc-(Ti, Al)N and with relatively large crystallites of ~ 9 nm. At higher bias voltages (−50 and −100 V), the coatings were found in dual phase fcc-(Ti, Al)N and fcc-AlN and the size of crystallites reduced to approximately 5 nm. The reduction of crystallite size and the increase of compressive residual stress with increasing bias voltage both contributed to an increase in hardness of the coatings.