Titanium Aluminum Nitride Coatings Research Articles

Characterisation of TiAlN PVD coatings on AZ31 magnesium alloy

Titanium aluminum nitride (TiAlN) coatings were deposited by radio frequency magnetron sputtering on AZ31 magnesium alloy. A microhardness tester, a surface profilometer and an electrochemical systems were used to investigate the hardness, thickness, and corrosion resistance of the coated AZ31 magnesium alloy. XPS showed the presence of different phases such as TiN, TiO2, TiON, AlN, and Al2O3. It demonstrated that TiAlN coatings improved the magnesium alloy’s surface hardness. Furthermore, TiAlN coatings also enhanced the corrosion resistance of the AZ31 magnesium alloy in 3.5 wt% NaCl solution. Corrosion current density decreased from 2.820 × 10−7 A/cm2 for the coated alloy to 1.066 × 10−5 A/cm2 for the uncoated one.

X-ray absorption near-edge structure of hexagonal ternary phases in sputter-deposited TiAlN films

Titanium aluminium nitride (TiAlN) coatings have been grown by reactive (Ar/N2) direct-current magnetron sputtering from a Ti50Al50 compound target. The film composition has been quantified by ion beam analysis showing the formation of Al-rich nitrides (Ti/Al∼0.3), with stoichiometric films for N2 contents in the gas mixture equal or above ∼25%. The surface morphology of the films has been imaged by atomic force microscopy, showing very smooth surfaces with roughness values below 2nm. X-ray and electron diffraction patterns reveal that the films are nanocrystalline with a wurzite (w) structure of lattice parameters larger (∼2.5%) than those for w-AlN. The lattice expansion correlates with the Ti/Al ratio in stoichiometric films, which suggests the incorporation of Ti into w-AlN. The atomic environments around Ti, Al and N sites have been extracted from the X-ray absorption near-edge structure (XANES) by recording the Ti2p, Al1s and N1s edges, respectively. The analysis of the XANES spectral lineshape and comparison with reported theoretical calculations confirm the formation of a ternary hexagonal phase.

Analysis of hardness of nanocrystalline coatings of aluminum-rich Ti1 − x Al x N

Titanium aluminum nitride coatings were fabricated by a d.c. magnetron sputtering system from a Ti–Al (60/40 wt%) target. Coatings were deposited on steel substrates, at a substrate temperature of 250 °C and a bias voltage of −80 V. The nitrogen flow was varied from 1·5–6 sccm and the Ar flow was kept constant at 20 sccm. The morphology and microstructure of the coatings were analysed by X-ray diffraction and scanning electron microscopy. The results of X-ray diffraction showed the presence of two cubic crystalline phases, TiN and AlN, which were confirmed by X-ray photoelectron spectroscopy. The Vicker hardness was obtained by the effective model of indentation. It was observed that the hardness of the coatings decreases from 22·8–9·5 GPa with an increased nitrogen content from 1·5–4·5 sccm. Subsequently, the hardness increased to 22·1 GPa by increasing nitrogen to 6 sccm. The behavior of hardness with grain size variation is consistent with the Hall-Peth relationship. The high value in the hardness of the coatings is mainly attributed to small grain sizes and the compressive stress present.

Application of Fuzzy Rule-Based Model to Predict TiAlN Coatings Roughness

In this work, an approach for predicting the roughness of Titanium Aluminum Nitride (TiAlN) coatings using fuzzy ruled-based model was discussed. TiAlN coatings were produced using magnetron sputtering process. Tungsten carbide (WC) was selected as the substrate and titanium alloy was used as the material to coat the cutting tool. The sputtering power, substrate bias voltage and substrate temperature were selected as the input variables while roughness of the TiAlN coatings was considered as the response variable. A statistical design of experiments method known as centre cubic design (CCD) was selected to collect the data for developing the fuzzy rules. The prediction performances of the fuzzy rule-based model with respect to percentage error, mean squared error (MSE), co-efficient determination (R2) and model accuracy were compared with the response surface regression model (RSM). The result shown that the fuzzy rule-based model has much better predicting capability compared to the RSM.

Influence of substrate roughness on structure and mechanical property of TiAlN coating fabricated by cathodic arc evaporation

The aim of the present research was to investigate the influence of different substrate roughness on structure and mechanical properties of Titanium Aluminium Nitride (TiAlN) coatings. Tungsten carbide rectangular block was used as substrate. Different surface roughness was achieved by using grinding discs with different grain sizes and diamond polishing powder, and TiAlN coatings were deposited on these substrates under the same preparation technique and parameters. Morphologies of substrates and coatings, crystal structure, thickness and mechanical properties of coatings were investigated using optical microscope, AFM, XRD, CSM scratch tester and tribometer. It was shown that surface morphology of cathodic arc TiAlN coating was mainly affected by the morphology of the substrate surface and the coating growth process. The influence of substrate roughness on crystal structure and thickness of the coatings could be ignored. With the decreasing of the substrate roughness, the adhesion force between coating and substrate increased. Three stresses model was applied to interpret this result. The wear resistance of the coating was also improved with decreasing the substrate roughness.

Wear performance of self-mating contact pairs of TiN and TiAlN coatings on orthopedic grade Ti-6Al-4V

Both titanium nitride (TiN) and titanium aluminum nitride (TiAlN) have shown great wear resistance potential in metallic medical devices as protective, hard thin film coatings. In the present study, the effects of TiN and TiAlN coating layers on the wear performance of Ti-6Al-4V were compared and analyzed. TiN and TiAlN coatings with a thickness of 3 µm were deposited by a cathodic vacuum arc ion plating technique on the surface of Ti-6Al-4V. Wear tests were conducted by using a pin-on-disk-type tribotester with a point contact self-mating pair in a linear reciprocal motion. A sliding distance of 20 mm per cycle at 1 Hz was used under a load of 15 N under ambient conditions with no lubricant. The wear resistance of TiN and TiAlN coatings is superior to that of uncoated Ti-6Al-4V at the early stage of sliding contact. Until a measurable amount of wear was detected, the number of sliding cycles of the TiAlN coating pair was longer than TiN. After the first detection of wear from the coating layers, the rate of wear of the TiN coating pairs was significantly higher than that of TiAlN (p < 0.05), and it was close to that of the uncoated pairs. In conclusion, the TiAlN coating is superior to TiN from the viewpoint of wear resistance under the test conditions used in this study.

Optical Detections From Worn and Unworn Titanium Compound Surfaces

Wear-induced roughness in terms of grooves, sharp ridges, and edges leads to scattering of the reflected light and leads unavoidably to a reduction of the optical signals in a standard specular geometry. However, by using a double-layer system consisting of titanium aluminum nitride (TiAlN) on top of a titanium nitride (TiN) layer we obtain an increase in the reflected light as a result of wear. The relative change of reflectance of light from the tribological TiAlN coated surface to the underlying layer of TiN is similar for non-worn surfaces and for surfaces exposed to an abrasive wear process. The induced roughness reduces the signals from worn samples, in a standard specular geometry, by up to 30% compared with unworn samples. Our model system of TiAlN coatings on top of ‘optical’ signal layers of TiN deposited on a 100Cr6 steel substrate, was exposed to a reciprocating wear process with up to 105 repetitive cycles in a linear tribometer. The worn TiAlN layers of thicknesses up to 3 μm, with strongly developed grooves and ridges, were subsequently used for the reflectance measurements. The results show that optical reflectance monitoring is a potential technique for intelligent determination of a residual thickness of realistic tribological coatings prior to complete wear.

Characterization and temperature controlling property of TiAlN coatings deposited by reactive magnetron co-sputtering

Titanium aluminum nitride (TiAlN) ternary coating is a potential material which is expected to be applied on satellite for thermal controlling. In order to investigate thermal controlling property, TiAlN coatings were deposited on Si wafers with different N 2 and Ar flux ratio by reactive magnetron co-sputtering. The structure, morphology, chemical composition and optical reflectance are investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), atom force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and spectrophotometer, respectively. The orientation of the coatings depends on the N 2/Ar flux ratio. The coatings deposited with N 2/Ar ratio of 10, 30 and 60% show the cubic-TiN [2 2 0] preferred orientation and the coating deposited with N 2/Ar ratio of 100% exhibits the phase of hexagonal-AlN and cubic-TiN. The surface of the coatings becomes more compact and smoother with the N 2/Ar ratios increase. XPS spectrum indicates that the oxides (TiO 2 and Al 2O 3), oxynitride (TiN x O y ) and nitrides (TiN and AlN x ) appear at the surface of the coatings. Ignoring internal power, the optimum equilibrium temperature of TiAlN coatings is 18 °C and the equilibrium temperature after heat-treated has slight change, which provides the prospective application on thermal controlling.

Properties and corrosion behaviour of reactive magnetron sputtered TiAlN coatings on AISI 316L SS in simulated bodily fluid

Because of their superior properties, titanium aluminium nitride (TiAlN) films are increasingly applied as protective layers on cutting and forming tools and turbine compressor blades and as biocompatible barriers. TiAlN films were deposited on AISI 316L stainless steel substrates by reactive magnetron sputtering using a target consisting of equal segments of titanium and aluminium. X-ray diffraction characterisation showed that the coating structure was face centred cubic. AFM and SEM studies indicated that the coatings are regular with dense shpherical granular structure. The coatings were also characterised using photoluminescence spectroscopy and Raman microscopy to elucidate the optical and acoustic phonon modes of the cubic lattices. Characteristic peaks were observed at 250, 620 and 1180 cm−1 in laser Raman studies. Polarisation and impedance spectroscopy studies on TiAlN and TiN coated specimens were conducted in Fusuyama simulated body fluid. The charge transfer resistance Rct increased in the order: uncoated 316L substrate; 2 μm TiN film; 3 μm TiN film; 2 μm TiAlN film. Thus, the TiAlN coating has the highest corrosion resistance, and was also found to have the most noble corrosion potential and lowest corrosion rate in the polarisation tests.

Gross slip fretting wear of CrCN, TiAlN, Ni, and CuNiIn coatings on Ti6Al4V interfaces

Fretting is a low amplitude oscillatory wear that occurs at component interfaces and can accelerate crack initiation as well as interfacial degradation. Prevalent in Ti-alloy contacts, fretting wear often occurs at the blade/disk interfaces of fan and compressor stages in turbine engines, causing premature component failure. In many cases, plasma sprayed CuNiIn (copper–nickel–indium) coatings and solid lubricants are applied to blade roots to mitigate the fretting problem. However, the CuNiIn coatings can cause severe damage to the uncoated Ti-alloy counter parts once the solid lubricants wear out. In this study, bench level gross slip fretting wear tests were conducted at room temperature on unlubricated Ti6Al4V (titanium, 6% aluminum, 4% vanadium) surfaces mated with CuNiIn and commercially pure Ni plasma sprayed surfaces. Upon analysis, it was determined that the uncoated Ti6Al4V surfaces initially gall. Then the resulting adherent wear particles break up causing a transition into a third body type wear mode over time. This leads to an accumulation of wear that is similar to that of uncoated Ti6Al4V mating surfaces. Additional tests were conducted after applying 2-μm thick PVD deposited TiAlN (titanium–aluminium–nitride) and CrCN (chrome–carbon–nitride) coatings to the surfaces of a second set of Ti6Al4V mating pairs. When worn against the unlubricated CuNiIn and Ni coatings, the thin TiAlN and CrCN coatings wore gradually without delaminating or cracking and were able to mitigate galling and extend test life. The application of the hard coatings lead to a reduction in wear in all of the tests except with the combination of TiAlN worn against CuNiIn.

Characterisation and applications of Cr–Al–N coatings

There is an increasing number of applications for hard coatings in engineering where both high oxidation resistance and hot hardness are required. One way to address this problem is to use hard ceramic coatings which are a combination of more than one metal so that the coating performance will benefit from the combined mechanical properties of the metals present. In this study, chromium aluminium nitride (Cr–Al–N), titanium nitride (Ti–N), titanium aluminium nitride (Ti–Al–N) and chromium nitride (Cr–N) coatings were deposited on 6.35 mm HSS drills and on hardened and polished AISI M2 steel test discs by means of electron beam plasma-assisted physical vapour deposition. For all depositions, the coating temperature was below 500 °C. Laboratory tests were performed to characterise the mechanical and tribological properties of the coatings. Along with the laboratory tests, accelerated drilling tests and actual industrial applications (punching and gear-shaping) were also used to evaluate the performance of the coatings. The results from the laboratory characterisation, drill tests and industrial applications all showed that Cr–Al–N performs exceptionally well compared to the industry “standards” of Ti–N, Ti–Al–N and titanium carbo-nitride (Ti–C–N). The exceptional performance of Cr–Al–N compared to the other coatings is considered with reference to the coatings’ characteristics.

Wear studies of (Ti–Al)N coatings deposited by reactive magnetron sputtering

Titanium–aluminium nitride coatings were deposited on stainless steel substrates by reactive dc magnetron sputtering using a composite target. Coatings were prepared by varying nitrogen flow ratio systematically. Wear studies of (Ti–Al)N coatings were studied methodically for all the coated samples. Wear tests were performed on Plint make reciprocating wear tester with ball-on-plate configuration (model TE-70). All the deposited samples were tested at 3 and 6 N loads and at 5 and 15 Hz frequencies against hard chrome steel balls. The tests were performed for two different durations of 10 and 30 min. To highlight the initial interaction mechanism of coating-ball interface, wear tests were also carried out on samples for shorter durations of 10, 30 and 60 s. Coatings were characterised, in addition, for phase analysis by X-ray diffraction, structure and compositional analysis by SEM coupled with EDAX and surface hardness by Knoop microhardness tester.

A comparative study of the mechanical strength of chemical vapor-deposited diamond and physical vapor-deposited hard coatings

Four mechanical parameters of physical vapor-deposited (PVD) hard coatings were obtained, which were the residual strain, Young's modulus, film toughness, and interface toughness, concerning titanium aluminum nitride (TiAlN) and titanium nitride (TiN) coatings deposited on WC–Co substrates. The results were quantitatively compared with the author's previous trials for the case of chemical vapor-deposited (CVD) diamond coatings. Due to the significant difference in the mechanical properties between PVD hard coatings and CVD diamond coatings, it was necessary to develop new experimental techniques, which could properly evaluate those parameters for the case of PVD hard coatings. As a conclusion, film toughness of PVD hard coatings was surprisingly brittle. It was an order of magnitude smaller than that of CVD diamond coatings. In contrast, no significant difference was found in interface toughness between these different kinds of coatings. Concerning the residual strain, TiN had far larger level than the other two. These differences in mechanical properties were further discussed in relation to the difference in their wear behavior.

A comparative study of magnetron co-sputtered nanocrystalline titanium aluminium and chromium aluminium nitride coatings

A comparative study of magnetron co-sputtered (Ti,Al)N and (Cr,Al)N coatings was made. It was found that while both coatings followed similar development pattern with increasing nitrogen pressure, the (Cr,Al)N coatings achieved much higher deposition rate and hardness, suggesting the coatings had a great potential for many industrial applications.

Grain refinement with increasing magnetron discharge power in sputter deposition of nanostructured titanium aluminium nitride coatings

Nanostructured titanium aluminium nitride coatings were produced via magnetron co-sputtering. The results showed the significant effect of magnetron discharge power on structural refinement of the coatings. As the aluminium magnetron power increased from 1.5 to 6.0 W/cm 2, the average grain diameter of the coatings was reduced from ∼210 to ∼90 nm.

Effect of target–substrate working distance on magnetron sputter deposition of nanostructured titanium aluminium nitride coatings

Nanostructured titanium aluminium nitride coatings were produced via magnetron sputtering. The target–substrate working distance showed significant effects on the microstructure and property development of the coatings. With a smaller working distance, densified, nanostructured ternary nitride coatings with substantially higher hardness were produced.

Oxidation resistance of titanium–aluminium–silicon nitride coatings

The demands for cutting tools tend to still longer service life and higher speed in cutting processes. To fulfil these demands, hard and wear resistant thin coatings have to be deposited on cutting tools. The functionality of the coating must be ensured at the high temperatures reached at the cutting edge during machining. At these temperatures, oxidation of the coatings may lead to problems. Titanium–aluminium nitride coatings show an oxidation behaviour superior to the widely used titanium nitride coatings. To further enhance the oxidation resistance, the addition of silicon to titanium–aluminium nitride films is analysed in this work. The investigated coatings were deposited by reactive DC magnetron sputtering on high-speed steel. The composition of the coatings could be varied by the type of target used and the applied voltage to each target and was determined by glow discharge optical spectroscopy (GDOS). The coating thickness is derived from ball cratering and ranges between 3 and 6 μm. The adhesion of the coatings is analysed by the scratch test. The coated samples are subjected to an oxidation test, where they are exposed to a temperature of 800 or 1000 °C and an oxygen partial pressure ranging between 1 and 100 mPa for 1 h. The results of the TiAlSiN coatings are compared with TiAlN coatings to evaluate the influence of the silicon. Ultra-microhardness measurements are performed prior and after the oxidation tests. Changes in the composition due to diffusion processes are measured with GDOS over the whole coating thickness and the coating/substrate interface. X-ray photoelectron spectroscopy reveals changes of composition and binding energy in the near surface zone.

A study on the microstructure and property development of d.c. magnetron cosputtered ternary titanium aluminium nitride coatings. Part III. Effect of substrate bias voltage and temperature

Advanced ternary (Ti,Al)N coatings were produced by reactive magnetron co-sputtering technique with separate titanium and aluminium targets at a 30° magnetron configuration under various substrate bias voltages and temperatures. The effect of substrate bias and temperature on the microstructure and property development of the coatings was investigated. It was found that an increase in substrate bias and/or substrate temperature imposed no major effect on the composition and phase formation of the (Ti,Al)N coatings, but had significant influence on the development of their microstructure and surface morphology. As the substrate bias and/or temperature increased, the coating structure was densified with development of fine grain size and reduced surface roughness, resulting in a substantial increase of the coating hardness. However as the substrate bias increased over 200 volts, excessive residual stress was built up, causing a fracture of the coatings. It is believed that the microstructure and property enhancement is attributed to an increased translational kinetic energy of the depositing atoms and a greater thermal energy provided to the substrate and the coating material with increasing substrate bias and/or temperature. The adatom mobility and the surface diffusion of atoms are enhanced to reduce the detrimental effects induced by the statistical roughening and self-shadowing of asputter deposition process. A densified zone T structure with low porosity and improved properties is produced.

Characterisation and performance of partially filtered arc TiAlN coatings

It is now being recognised that the level of residual stress in physical vapour deposited (PVD) coatings is yet another important physical property of thin film PVD coating parameters that can critically affect their performance. In this study, titanium aluminium nitride (TiAlN) coatings were deposited using a dual source filtered arc evaporation system with a view to determine the effect of bias voltage increased from −50 to −250 V, the residual stress in the coating as well as the adhesion and cutting tool performance. The X-ray diffraction methods of Bragg–Brentano and glancing angle parallel beam (sin 2ψ) were used to study the texture and residual stress in the as-deposited coatings. The results showed that as the bias voltage increased from –50 to –250 V and the residual stress increased from 7.67 to 11.81 GPa (compressive). However, little change in residual stress was observed with an increase in arc current from 75 to 175 A. All coatings exhibited a preferred orientation in the {111} direction, however, a reduction in the {111} intensity was observed for the coating deposited at –50 V. Coating hardness was observed to increase from 26.3 to 31.7 GPa when the bias voltage was increased from –50 to –150 V. However, no further increase was observed at –250 V. No effect on hardness was noted for any change in arc current. Scratch adhesion results showed little effect on the bias voltage with critical load values of 46, 48 and 43 N for the −50, −150 and −250 V biased coatings, respectively. However, increasing the arc currents above 75 A resulted in a reduction of critical load from 48 N for 75 A to 36 and 37 N for 125 and 175 A arc currents, respectively. Damiler Benz Rockwell ‘C’ adhesion tests carried out also revealed a similar trend. The Al content of the coating was found to decrease with increasing bias voltage but increase with an increase in arc current. Accelerated drill life tests suggested that an increase in residual stress associated with the higher bias voltages does affect tool life. For arc current variation, the balance between intrinsic and extrinsic stresses that contribute to the total residual stress may affect cutting tool life.

Dry cutting performance of partially filtered arc deposited titanium aluminium nitride coatings with various metal nitride base coatings

PVD titanium aluminium nitride coatings are known to improve the performance of cutting tools in aggressive machining applications, such as high-speed dry machining. This is generally acknowledged to be due to the fact that these coatings are able to maintain high hardness and resistance to oxidation at the elevated temperatures typically experienced in such metal cutting applications. In this investigation, the performance of single layer coatings of TiN and CrN, and double layer coatings of TiN/TiAlN and CrN/TiAlN were assessed on Co-HSS drills used to machine grey cast iron. It was found that the CrN coatings performed as well as the TiN coatings when drilling grey cast iron. In addition, the double layer coatings outperformed the single layer coatings with the CrN/TiAlN coatings having a 20% improvement in tool life compared with the TiN/TiAlN-coated drills. This result is particularly interesting since the Daimler–Benz indentation test suggested that the TiN/TiAlN had much lower adhesion than the CrN/TiAlN. These results are discussed in terms of an analysis of the physical and mechanical properties of the coatings but it highlights the need for meaningful measurement of critical coating properties which might relate to their performance in metal cutting.