Ti1-xAlxN Coatings Research Articles

Dependence of protective effect of Ti1–xAlxN coatings in 3 wt.% NaCl solution on dissolution mechanism of their phases c‐Ti0.5Al0.5N, c‐AlN, and c‐TiN

AbstractThe dissolution mechanism of phases c‐Ti0.5Al0.5N, c‐aluminium nitride (AlN), c‐TiN, and Al2Ti, and elements of the Ti1–xAlxN coatings (for x < 0.6) in 3 wt.% NaCl solution is described based on the results of X‐ray diffraction analysis, energy‐dispersive X‐ray spectroscopy, and scanning electron microscope and previous electrochemical tests. Researchers studied the protective effectiveness of Ti1–xAlxN coatings in 3 wt.% NaCl solution by analyzing the factors: composition, thickness, porosity, total energy of ground state, stresses, structure, and texture. It was first established that the additional c‐TiN phase with Rpmax and Ecormax, and secondary phase Ti0.70–0.82N formed after Al's dissolution in the main phase c‐Ti0.5Al0.5N increases the N content and prevents the Ti dissolution in the Ti1–xAlxN coatings. The phase c‐AlN with icormin reduces the dissolution rate of Al in the c‐Ti0.5Al0.5N phase. The stoichiometric c‐Ti0.5Al0.5N is the most thermodynamically stable phase. The described phase transformations in Ti1–xAlxN coatings during phases dissolution in 3 wt.% NaCl can predict the coating protective effect. A multilayer coating with layers of c‐AlN, c‐TiN, and c‐Ti0.5Al0.5N is recommended for industrial use.

Strain and phase evolution in TiAlN coatings during high-speed metal cutting: An in operando high-energy x-ray diffraction study

We report on phase and strain changes in Ti1-xAlxN (0 ≤ x ≤ 0.61) coatings on cutting tools during turning recorded in operando by high-energy x-ray diffractometry. Orthogonal cutting of AISI 4140 steel was performed with cutting speeds of 360–370 m/min. Four positions along the tool rake face were investigated as a function of time in cut. Formation of γ-Fe in the chip reveals that the temperature exceeds 727 °C between the tool edge and the middle of the contact area when the feed rate is 0.06 mm/rev. Spinodal decomposition and formation of wurtzite AlN occurs at the positions of the tool with the highest temperature for the x ≥ 0.48 coatings. The strain evolution in the chip reveals that the mechanical stress is largest closest to the tool edge and that it decreases with time in cut for all analyzed positions on the rake face. The strain evolution in the coating varies between coatings and position on the rake face of the tool and is affected by thermal stress as well as the applied mechanical stress. Amongst others, the strain evolution is influenced by defect annihilation and, for the coatings with highest Al-content (x ≥ 0.48), phase changes.

Mechanical and thermal properties of AlN/Ti1-xAlxN (x = 0, 0.45 and 0.62) multilayers

Ti1-xAlxN coatings with face-centered cubic structure are widely used as wear-resistant protective materials. Construction of multilayer architecture is an efficient method to tailor the properties of Ti1-xAlxN coatings. In this work, the structure, mechanical and thermal properties of AlN/Ti1-xAlxN (x = 0, 0.45 and 0.62) multilayers as well as corresponding monolithic coatings are studied. Monolithic TiN, Ti0.55Al0.45N and Ti0.38Al0.62N coatings exhibit single cubic structure, corresponding to their hardness of ~26.4, 28.6 and 32.7 GPa, respectively. The epitaxial growth between AlN and TiN (Ti0.55Al0.45N) layers increases the hardness to ~30.5 and ~31.4 GPa, whereas the AlN/Ti0.38Al0.62N multilayer with incoherent interface only has a hardness of ~24.2 GPa. Even if the AlN insertion layer promotes the thermal decomposition of Ti0.55Al0.45N coating, the AlN/Ti0.55Al0.45N coating still present a higher hardness than Ti0.55Al0.45N coating during annealing up to 1000 °C. The AlN insertion layer has a positive effect on the Ti1-xAlxN coatings regardless of coherent and incoherent interfaces. Especially, the oxidation resistance of AlN/Ti1-xAlxN multilayers is predominantly influenced by the total Al content rather than the interfacial states. The AlN/Ti0.38Al0.62N multilayer with incoherent interface behaves the best oxidation resistance.

Influence of deposition parameters on microstructure and mechanical properties of chemical vapor deposited Ti1-xAlxN coatings

Using thermally activated chemical vapor deposition (CVD), it is possible to synthesize Ti1-xAlxN coatings with Al contents up to x > 0.8 in a face-centered cubic crystal structure. This is considered to be due to their quite high global Al content and due to the frequently observed self organized nanolamellar microstructure consisting of lamellae with high Al contents of x > 0.9 epitaxially stacked with lamellae where x ∼ 0.5. However, CVD is a complex process and the formation mechanism of the lamellae and the resulting coating properties are not yet fully understood. Here, we have investigated the impact of the deposition temperature, deposition pressure and rotation speed of the reactive gas feed on the microstructure and mechanical properties. Our results show that by varying the pressure between 10 and 185 mbar and the temperature between 700 and 820 °C the grain size and texture can be tailored. In addition to the amount of wurtzitic AlN formed, they govern the mechanical properties. Similarly, the nanolamella periodicity strongly depends on temperature and pressure, indicating that the reaction kinetics are responsible for their formation rather than the gas feed rotation.

Visualising microstructural dynamics of titanium aluminium nitride coatings under variable-temperature oxidation

Understanding the link between titanium-aluminium nitride’s (Ti1-xAlxN) physicochemical properties and structural dynamics during operation is essential to designing and fabricating advanced ceramic coatings. Here, we directly visualise the oxidation of Ti1-xAlxN (for x = 0, 0.18, 0.44, & 0.67) coatings from 100 to 1000 °C using environmental transmission electron microscopy (ETEM) imaging and energy dispersive X-ray spectroscopy (EDX) analysis. The high-frame-rate ETEM movies show that oxidation in TiN proceeds at the grain boundaries and cracks; in contrast, Ti1-xAlxN coatings transform from large as-deposited grains into oxide nanoparticles. Moreover, high-resolution ETEM imaging show the presence of anatase TiO2 at the early stages of oxidation across all compositions. Above ∼ 850 °C, the oxide nanoparticles grow through crystal merging, diffusion and recrystallisation to form rutile TiO2. The EDX elemental maps coupled with secondary electron imaging reveal a uniform TiO2 sublayer decorated with increasing coverage of Al2O3 particles for x = 0.18 to 0.44. In contrast, coatings with x = 0.67 reveal a complete in-plane phase separation of Al- and Ti-oxides, which can rationalise their decreasing long-term oxidation resistance. Finally, the study provides unique insight into the real-time structural dynamics underpinning the oxidation resistance of Ti1-xAlxN coatings.

Structural changes in Ti1-xAlxN coatings during turning: A XANES and EXAFS study of worn tools

Structural changes in Ti1-xAlxN coated tool inserts used for turning in 316L stainless steel were investigated by XANES, EXAFS, EDS, and STEM. For coarse-grained fcc-structured Ti1-xAlxN coatings, with 0 ≤ x ≤ 0.62, the XANES spectrum changes with Al-content. XANES Ti 1s line-scans across the rake face of the worn samples reveals that TiN-enriched domains have formed during turning in Ti0.47Al0.53N and Ti0.38Al0.62N samples as a result of spinodal decomposition. The XANES spectra reveal the locations on the tool in which the most TiN-rich domains have formed, indicating which part of the tool-chip contact area that experienced the highest temperature during turning. Changes in the pre-edge features in the XANES spectra reveal that structural changes occur also in the w-TiAlN phase in fine-grained Ti0.38Al0.62N during turning. EDS shows that Cr and Fe from the steel adhere to the tool rake face during machining. Cr 1s and Fe 1s XANES show that Cr is oxidized in the end of the contact length while the adhered Fe retains in the same fcc-structure as that of the 316L stainless steel.

Роль фазового и элементного состава, структуры и текстуры покрытий AlN и Ti1-xAlxN в их защитном эффекте

Phase and elemental composition of AlN and Ti1-xAlxN coatings in their protective effect in a 3% wt NaCl solution, are exam-ined.
 The dependences of the corrosion current density and polarization resistance of AlN and Ti1-xAlxN coatings on the ratio of Al/Ti and phases enriched with aluminum c-AlN + h-AlN and titanium c-TiN + h-Ti3Al2N2 are found. The possibility of controlling the corrosion properties of coatings is shown

Evolution of the fracture properties of arc evaporated Ti1-xAlxN coatings with increasing Al content

Although the positive effect of an increasing Al content in Ti1-xAlxN hard coatings within the cubic regime is thoroughly investigated, there is a lack of systematic studies on the fracture properties. Thus within the present work, seven Ti1-xAlxN coatings with increasing Al content from x = 0 up to x = 0.78 were deposited by cathodic arc evaporation. Using scanning electron microscopy and X-ray diffraction, a grain refinement with increasing Al content up to x = 0.65 could be observed, while the coating with the highest Al content of x = 0.78 showed again a coarser grain size. The presence of a single phase face-centered cubic (fcc)-structure up to an Al content of x = 0.49 was confirmed by X-ray diffraction. Ti0.44Al0.56N and Ti0.35Al0.65N exhibited a dual phase fcc- and wurtzitic (w)-structure, where for the latter the w-structure is dominating. A single phase w-structure was observed for the Ti0.22Al0.78N coating. Nano-indentation experiments revealed an increasing hardness with increasing Al content up to x = 0.56 and thus, as long as the fcc-phase is dominating, due to decreasing grain size and increasing compressive stress. For the coatings with dominating and pure w-structure a drop in hardness was observed. Similar to the hardness, the micromechanical bending tests also revealed improving fracture properties with increasing Al content up to x = 0.56 and deteriorating fracture properties when the w-structure becomes dominant.

Impact of oxygen content on the thermal stability of Ti-Al-O-N coatings based on computational and experimental studies

Recently, the favorable impact of O-addition on the oxidation resistance, toughness and machining performance of Ti1-xAlxN coatings has attracted a wide range of research interests. We systematically studied the effect of O-addition on structure, mechanical and thermal properties of Ti1-xAlxN coatings by experimental and theoretical methods. The hardness values of Ti0.42Al0.58N0.95, Ti0.41Al0.59(O0.08N0.92)1.02, Ti0.41Al0.59(O0.12N0.88)1.06 and Ti0.41Al0.59(O0.18N0.82)1.13 with face-centered cubic (c) structure are 31.8 ± 0.7, 31.9 ± 0.6, 32.1 ± 0.8 and 31.7 ± 0.8 GPa, respectively. Thus, incorporation of oxygen into Ti1-xAlxN has no impact on the hardness (within the investigated range) of the films in their as-deposited state. After annealing, the peak hardness increases with the oxygen content and is 34.3 ± 0.7 GPa with 900 °C, 35.1 ± 0.8 GPa with 1100 °C and 35.9 ± 0.5 GPa with 1100 °C for Ti0.42Al0.58N0.95, Ti0.41Al0.59(O0.08N0.92)1.02 and Ti0.41Al0.59(O0.12N0.88)1.06, respectively. First-principles calculations combing the climbing image nudged elastic band (CI-NEB) method reveal that the incorporated oxygen retards the thermal decomposition by increasing the diffusion activation energy for Al diffusion. First-principles calculations further show that the most preferred decomposition products of c-Ti1-xAlx(OyN1-y)z are c-TiOyN1-y and c-AlN. Moreover, although the highest oxygen-containing film, Ti0.41Al0.59(O0.18N0.82)1.13, contained a noticeable quantity of wurtzite (w-)AlN when annealed at 1200 °C, the sample exhibits the peak hardness of 35.5 ± 0.8 GPa. This, we attribute to the strengthening effect due to the precipitation of nano-sized α-Al2O3 and θ-Al2O3.

Structural and phase transformations control in Ti and Al cathode materials, WC-Co substrate, and Ti1-xAlxN coating to improve their physico-mechanical and wear properties

The paper analyzed temperature ranges of aggregate/polymorphic state changes, phase and structural transformations in Al, Ti, WC-Co, and Ti1-xAlxN, leading to the gradient of thermo-physical and physico-mechanical properties of cathodes, substrate, and coating. The critical temperatures for Al and Ti are the points of the exo- or endothermic effect occurrence at 933 K (TmAl) and 1155.5 K (Tα-Ti→β-Ti), respectively. The hardness of the WC-Co / Ti1-xAlxN composition varies with the heating temperature of the WC-Co before coating deposition. The optimal heating interval for WC-Co is 873…963 K. The structuring process of the Ti1-xAlxN coating was investigated in the temperature range 673…1073 K before the spinodal decomposition of c-TiAlN into metallic c-TiN and dielectric-semiconductor c-AlN. Physico-mechanical properties of the Ti1-xAlxN coatings were determined using a FISCHERSCOPEH100C measurement system per the standard DINENISO14577-1. Wear tests were carried out according to the “finger-disk” scheme in a coolant-cutting fluid on a laboratory friction machine. The optimal temperature conditions for the deposition of a nanostructured Ti1-xAlxN coating with a minimum phase and elemental composition gradient and microdroplets number, a complex of high physico-mechanical properties, wear, and cracking resistance have been established. The Ti1-xAlxN coatings efficiency has been increased by controlling the thermo-physical and physico-mechanical properties of Ti and Al cathodes, the substrate (hard alloy WC-Co), and the Ti1-xAlxN coating in-process of their heating and cathodic arc evaporation. Multifunctional dependency graphs of the physico-mechanical properties and the friction coefficient of the Ti1-xAlxN coatings on the Al = x content have been developed. The relationship between the resistance of the coating to plastic deformation and the coefficient of friction has been established.

Influence of the deposition parameters on the nanolamella periodicity of chemical vapor deposited Ti1-xAlxN

Owing to its extraordinary nanolamellar microstructure, chemical vapor deposited Ti1-xAlxN has gained considerable interest in the recent years. However, the formation mechanism of the nanolamellae is not yet understood and is currently subject of intense research. In this publication we have deposited Ti1-xAlxN coatings at varying temperature, pressure and rotation speed of the central gas feed. Transmission electron microscopy has been conducted in order to quantify the lamella periodicity and correlate it with the deposition parameters. This work demonstrates that nanolamellae can be obtained over a wide range of deposition parameters and, more importantly, that the periodicity does not seem to depend on the gas feed rotation but can be correlated with deposition temperature and pressure.

Crater wear mechanism of TiAlN coatings during high-speed metal turning

The influence of the aluminium content (x) on crater wear mechanisms of Ti1-xAlxN coated WC-Co inserts in high-speed turning of 316L stainless steel was investigated. Electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the wear behaviour. Ti1-xAlxN coatings with x ≤ 0.53 showed, after 1/3 of the tool life, a thick adhered layer composed of oxides and metallic species from the steel, and no diffusion of workpiece material into the coating. These coatings presented the best wear resistance and least abrasive wear. The high aluminium content Ti0·38Al0·62N coating showed the worst crater wear resistance. This is assigned to interdiffusion of workpiece elements and oxygen into the coating as a consequence of spinodal decomposition of the cubic TiAlN-phase, resulting in more severe abrasive wear.

Effect of Ta alloying on isothermal oxidation behavior of DC magnetron sputtered Ti1-xAlxN coatings on titanium substrate

Oxidation behavior of magnetron sputtered Ti1-x-yAlxTayN coatings (with y varied from 0.1 to 0.35) on titanium substrates was studied upon isothermal exposure in air at 850 and 950 °C in comparison with a Ti0.45Al0.55N coating. It was found that the Ti1-x-yAlxTayN coatings demonstrate substantially improved protective properties at a temperature of 850 °C while this effect is only slightly pronounced at 950 °C. The protective properties of the Ti1-x-yAlxTayN coatings at 950 °C were found to deteriorate with increasing the Ta content so that only the Ti0.41Al0.49Ta0.10N composition provided reasonably effective protection of the underlying titanium substrate.

Thermal stability and machining performance of arc evaporated Ti1-xAlxN hard PVD coatings with x=0.5 – 0.73 ratios using an integrative approach

Incorporating Al into TiN-based coatings plays a key role in enhancing their mechanical properties and thermal stability which are the crucial properties for cutting tool applications. In this paper, we study the effect of different Al contents on the mechanical and thermal properties and consequent machining performance using an integrative approach. The results show that heat treatment of the Ti1-xAlxN coating decomposes them into their substituents, which is accompanied by the formation of c-AlN and c-TiN domains. The coherency strain between these domains results in increased hardness values under temperatures up to ~900–1000 °C. This growth was found to be substantial in cases with a single-phase cubic structure. In the coating sample with lower Al contents, where a cubic structure is present, the machining performance tended to be superior mainly due to improved adhesion to the substrate, higher hardness, and compressive residual stress.

Influence of pulsed-substrate bias duty cycle on the microstructure and defects of cathodic arc-deposited Ti1-xAlxN coatings

The influence of pulsed substrate bias duty cycle on the growth, microstructure, and defects of Ti 1-x Al x N coatings grown by cathodic arc deposition was investigated. Ti 1-x Al x N coatings of varying compositions (x = 0.56, 0.38, 0.23) were deposited on cemented carbide substrates with 10, 25, 50, and 95% duty cycles of −50 V pulsed-bias under 10 Pa of pure N 2 gas. Coatings grown at low duty cycles (10 and 25%) showed strongly textured, under-dense coatings with facetted columns and low amount of lattice defects. Applying higher duty cycles (50 and 95%) produced coatings that have denser microstructures, less preferred orientation, increasing compressive stresses and increased lattice defect densities. Our study elucidates how duty cycle variation not only changes the overall average energy supplied at the growth front but also kinetically influences the coating growth and thus microstructure and defect structure. • Ti 1-x Al x N coatings were grown on WC-Co substrates with 10, 25, 50, and 95% duty cycles of -50 V pulsed-substrate bias. • Duty cycle variation significantly and systematically affected their growth, microstructure, and crystallographic defects. • Low duty cycle conditions produced textured, under-dense coatings with facetted columns and low amount of lattice defects. • Higher duty cycles produced coatings that have denser microstructures, less texture, compressive stresses and increased lattice defects. • Duty cycle change was a powerful tool to achieve arc coatings with low defect density, high crystal quality and low stress.

CVD TiAlN coatings with tunable nanolamella architectures

In this work, Ti1-xAlxN (TiAlN) coatings were synthesized by low pressure chemical vapour deposition (LPCVD), and the influence of a rotational precursor gas supply on the coating microstructure was studied. The microstructure of the TiAlN coatings were characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and electron backscattered diffraction (EBSD). It is shown that a rotational precursor gas supply induces an oscillatory surface reaction, which causes a nanolamella architecture. When the gas beam directly hits the sample, the local gas flow velocity is high, which increases the deposition rate of Ti and a Ti(Al)N lamella is formed. When the gas beam rotates away, the local gas velocity is low, so the deposition rate of Ti decreases, and an Al(Ti)N lamella is formed. As this is repeated a periodic nanolamella architecture is formed. The nanolamellae grow epitaxially on three {001} facets of the 111 textured grains, which leads to a pyramidal surface morphology. Without gas supply rotation, a high Al content cubic phase was still obtained, but no nanolamella was formed. This indicates that Ti-rich lamellae are not necessary to stabilize an Al-rich cubic TiAlN phase. In addition, spinodal decomposition is not likely to be the driving force behind the nanolamella formation in LPCVD TiAlN, as this would also have happened in the sample without a rotational gas supply. Finally, the nanolamella periodicity is found to be tunable via controlling the rotation speed of the precursor supply relative to the coating growth rate.

Thermal stability and oxidation resistance of architecturally designed Ti–Al–N- and Ti–Al–Ta–N-based multilayers

Omnipresent demands for enhanced mechanical properties under thermal load and increased oxidation/corrosion resistance trigger further developments of Ti1-xAlxN coatings. We here combine the beneficial alloying with Ta and architectural coating design by developing ~3-μm-thick Ti-Al-N/Ta-Al-N and Ti-Al-Ta-N/Ta-Al-N multilayers. Recently, we showed that especially the combination of 17–25 nm thin arc evaporated Ti0.55Al0.45N or Ti0.51Al0.43Ta0.06N layers with 3–4 nm thin reactively sputtered Ta0.77Al0.23N or Ta0.57Al0.43N layers leads to excellent properties in the as-deposited state.Here, we study their thermal stability in vacuum and ambient air in more detail.The multilayers clearly outperform their individual monolithically grown counterparts, Ti0.55Al0.45N, Ti0.51Al0.43Ta0.06N, Ta0.77Al0.23N, or Ta0.57Al0.43N during oxidation tests at 850 and 950 °C. From the latter, only the Ti0.51Al0.43Ta0.06N coating was not fully oxidised (the remaining nitride layer was ~1 μm) after the 25-h-oxidation treatment at 850 °C. However, after 25 h at 950 °C, also this coating was fully oxidised. The Ti0.51Al0.43Ta0.06N/Ta0.77Al0.23N multilayers even survived the 25 h–oxidation at 950 °C (~2 μm of the initial coating thickness still remaining). This multilayer also outperforms the other investigated coatings and multilayers with respect of mechanical properties after different annealing treatments in vacuum up to 1200 °C.Based on these results we can conclude that the combination of arc evaporated Ti0.51Al0.43Ta0.06N layers with sputtered Ta0.77Al0.23N layers (realised with an industrial hybrid process) not only leads to excellent mechanical properties after subject to thermal exposure but also excellent oxidation resistance.

Comparison of corrosion, physico-mechanical and wear properties of TiN, ZrN, TixZr1-xN and Ti1-xAlxN coatings

In this paper, TiN, ZrN, TixZr1-xN, Ti1-xAlxN coatings were obtained by cathodic arc evaporation at optimal technological parameters. The corrosion properties of these coatings were investigated in 5% NaOH. The coating ZrN deposited by cathodic arc evaporation slows down the corrosion in the 5% NaOH by over 3,000 times, and the passive current – by 2,000 times. The TixZr1-xN coating has the best physico-mechanical properties: microhardness Н = 36 GPa, Young’s modulus Е = 312 GPa, elastic recovery We = 78 %, resistance to elastic failure strain H/E = 0.12, and resistance to plastic strain H3/E2 = 1.31 GPa. The Ti1-xAlxN coating has the best wear properties: friction coefficient 0.09, counterbody wear intensity by volume 0.43•10-8 mm3/Nm, coating wear intensity by volume 0.05•10-4 mm3/Nm and by mass•0.03•10-5 mg/Nm. Multilayer coating TiN-TixZr1-xN-Ti1-xAlxN-ZrN (ZrN-top layer) has a complex of high physico-mechanical and wear properties in 5% NaOH.

Effects of gas flow on detailed microstructure inhomogeneities in LPCVD TiAlN nanolamella coatings

Depositing homogeneous TiAlN coatings with a high Al content on cutting tool inserts is a challenging task. In this work, high-Al cubic Ti1-xAlxN coatings (average x = 0.8) with periodic Ti(Al)N (x = 0.5) and Al(Ti)N (x = 0.9) nanolamellae structure were synthesized by low pressure chemical vapour deposition (LPCVD) with different gas flow velocities, and the detailed microstructure was investigated by electron microscopy and simulations. Using a high gas flow rate, the columnar TiAlN grains with regular periodic nanolamella structures disappeared, the coating became enriched in Ti and hexagonal AlN (h-AlN) formed in the coating. The high Ti content is suggested to be caused by the high gas flow rate that increases the mass transport of the reactants. However, this does not influence the Al-deposition much as it is mainly limited by the surface kinetics due to the relatively low deposition temperature. Density functional theory (DFT) modelling and electron microscopy showed that h-AlN tends to form on the Ti(Al)N phase with a specific crystallographic orientation relationship. The Ti enrichment due to high gas flow rate promotes the formation of h-AlN, which therefore deteriorates the nanolamella structure and causes the disappearance of the columnar TiAlN grains. Thus, by designing the CVD process conditions to avoid too high gas flow rates, homogenous TiAlN coatings with high Al content and nanolamella structures can be deposited, which should yield superior cutting performance.

Deformation behaviour of TiN and Ti–Al–N coatings at 295 to 573 K

Temperature-dependent nanoindentation testing was employed to investigate the deformation behaviour of magnetron sputtered (100) TiN and Ti1-xAlxN (x = 0.34, 0.52, 0.62) coatings in the temperature range from 295 to 573 K. The maximum temperature is sufficiently below the deposition temperature of 773 K to guarantee for stable microstructure and stress state during testing. The TiN coating displayed the same hardness as bulk single crystal (SC) TiNbulk. The addition of aluminium to TiN (to form single-phase face centred cubic structured Ti1-xAlxN coatings) increased the room temperature hardness due to increased bond strength, lattice strain and higher activation energy for the dislocation slip. For coatings with a low aluminium content, Ti0.66Al0.34N, the decrease in hardness with temperature was similar to the TiN coating and SC-TiNbulk. In contrast, the hardness of coatings with moderate, Ti0.48Al0.52N, and high, Ti0.38Al0.62N, aluminium contents varied little up to 573 K. Thus, the Ti1-xAlxN matrix is mechanically more stable at elevated temperatures than its TiN relative, by providing a lower decrease in lattice resistance to the dislocation flow with increasing temperature. The findings suggest that the addition of Al to TiN (to form Ti1-xAlxN solid solutions) not only improves the hardness but also leads to stable hardness with temperature, and emphasizes the importance of bonding states and chemical fluctuations, next to structure and morphology of the coatings that develop with changing the chemistry.