Cathodic Arc Evaporation Research Articles

Tailoring the Hybrid Magnetron Sputtering Process (HiPIMS and dcMS) to Manufacture Ceramic Multilayers: Powering Conditions, Target Materials, and Base Layers.

The mechanical and wear behavior of CrN/CrAlN multilayers were improved by tailoring the experimental conditions of a hybrid magnetron sputtering process based on a high-power impulse (HiPIMS) and two direct current magnetron sputtering (dcMS) power supplies. To this end, the influence of the base layer and of the combination of Cr and CrAl targets, which were switched to the dcMS and HiPIMS power supplies in different configurations, were investigated with respect to the growth of ceramic CrN/CrAlN multilayers onto commercial gas-nitrided diesel piston rings. The microstructure, grain morphology, and mechanical properties were evaluated by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and instrumented nanoindentation. Bench wear tests simulating the operation of a combustion engine were conducted against a gray cast iron cylinder liner under reciprocating conditions using 0W20 oil as a lubricating agent enriched with Al2O3 particles. The results revealed a significant increase in hardness, resistance to plastic strain, and wear resistance when two CrAl targets were switched to a HiPIMS and a dcMS power supply, and a Cr target was powered by another dcMS power supply. The compressive coating stresses were slightly reduced due to the soft Cr base layer that enabled stress relief within the multilayer. The proposed concept of hybrid magnetron sputtering outperformed the commercial PVD coatings of CrN for diesel piston rings manufactured by cathodic arc evaporation.

Tailoring the scratch adhesion strength and wear performance of TiNiN nanocomposite coatings by optimising substrate bias voltage during cathodic arc evaporation

The tribological properties of TiN-based coatings can be substantially influenced by the choice of substrate bias employed during physical vapor deposition. However, the effects of applied substrate bias voltages during cathodic arc evaporation on to the scratch adhesion strength and wear resistance of TiNiN coatings have not been previously studied. In this present work, a series of TiNiN coatings were fabricated onto tool steel (M2) substrates using the cathodic arc evaporation method by applying a range of bias voltages to the substrate. The aim of this study is to investigate the scratch response and wear performance of these coatings along with an investigation of the deformation mechanisms in operation during scratch and wear tests. The best scratch adhesion strength (i.e., greater LC1, LC2 and CPRs values) was noted for the coating prepared at a bias voltage of −100 V, which was ascribed to the synergistic responses arising from superior mechanical properties, the influence of a high compressive residual stress and a fine, equiaxed nanocomposite structure, that acted to promote effective resistance against cohesive and adhesive failure. Further, the failure mechanisms under progressive loading conditions were also investigated through observation of the complex crack patterns generated, compressive residual stress values and the coatings' hierarchical design. An approximately 85 % enhancement in wear resistance for these TiNiN coatings was achieved as the bias voltage was increased from 0 V to −100 V. This −100 V coating exhibited the highest values of H/Er (>0.1) and We (>60 %), as well as the highest Ni concentration (~ 4 at.%).

Influence of ion irradiation-induced defects on phase formation and thermal stability of Ti0.27Al0.21N0.52 coatings

The influence of changes induced by ion irradiation on structure and thermal stability of metastable cubic (Ti,Al)N coatings deposited by cathodic arc evaporation is systematically investigated by correlating experiments and theory. Decreasing the nitrogen deposition pressure from 5.0 to 0.5 Pa results in an ion flux-enhancement by a factor of three and an increase of the average ion energy from 15 to 30 eV, causing the stress-free lattice parameter to expand from 4.170 to 4.206 Å, while the chemical composition of Ti0.27Al0.21N0.52 remains unchanged. The 0.9% lattice parameter increase is a consequence of formation of Frenkel pairs induced by ion bombardment, as revealed by density functional theory (DFT) simulations. The influence of the presence of Frenkel pairs on the thermal stability of metastable Ti0.27Al0.21N0.52 is investigated by scanning transmission electron microscopy, differential scanning calorimetry, atom probe tomography and in-situ synchrotron X-ray powder diffraction. It is demonstrated that the ion flux and ion energy induced formation of Frenkel pairs increases the thermal stability as the Al diffusion enabled crystallization of the wurtzite solid solution is retarded. This can be rationalized by DFT predictions since the presence of Frenkel pairs increases the activation energy for Al diffusion by up to 142%. Hence, the thermal stability enhancement is caused by a hitherto unreported mechanism - the Frenkel pair impeded Al mobility and thereby retarded formation of wurtzite solid solution.

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.

The Impact of Bias and Nitrogen Pressure on TiNbN Coatings in Arc-PVD Processes—A Multifactorial Study

Titanium-based nitride physical vapour deposition (PVD) coatings, such as titanium nitride (TiN), are state-of-the-art solutions for surface modifications of CoCrMo-based implants for patients who are hypersensitive to metallic ions such as cobalt, chromium and nickel. Variations of the process parameters during the cathodic arc evaporation are known to exhibit an impact on the surface properties of coatings. The aim of this study was to characterise the effect of the substrate bias and the nitrogen pressure on the surface properties of TiNbN coatings deposited on CoCrMo alloys in a limited parameter set. Eighteen parameter sets were coated with TiNbN. The substrate bias (−100 to −200 V) and the nitrogen pressure (0.3–3.0 Pa) were selected following a randomised, multifactorial response surface test design. The coating thickness, roughness, hardness and scratch resistance were measured following standardised procedures. The structure of the coating was analysed by SEM and XRD. The substrate bias and the pressure exhibited a significant impact on the coating thickness and the surface roughness. The grain growth was predominantly impacted by the bias. The parameter variation did not show any significant impact on the XRD, hardness or scratch test results.

Improving the mechanical, tribological, and electrochemical behavior of AISI 304 stainless steel by applying CrN single layer and Cr/CrN multilayer coatings

The purpose of this study was to assess the mechanical and tribological behavior of chromium nitride (CrN) single layer and multilayer nanostructured coatings of chromium/chromium nitride (Cr/CrN) applied on AISI 304 stainless steel to be used in a marine application. CrN and Cr/CrN coatings were performed using cathode arc evaporation a division of physical vapor deposition (CAE-PVD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM) were utilized for phase identification of coatings and surface morphology, respectively. Nano-indentation method was used to investigate the mechanical behavior of coatings. The tribological behavior of the coatings was studied by the ball-on-disk method. The results indicate that the mechanical behavior of the Cr/CrN multilayer nanostructured coatings is better in comparison to the CrN single-layer coatings. The hardness values of CrN and Cr/CrN coatings were 21.5 and 23.3 GPa, respectively. The higher hardness of the nanolayered coating might be owing to blocking the movement of dislocations and microcracks by its layered structure. Furthermore, the tribological behavior of AISI 304 stainless steel was highly amended by applying the coatings. The coefficient of friction for CrN and Cr/CrN coatings in a dry condition decreased from 0.61 to 0.49 and 0.46, respectively. Also, the CoF value reduced from 0.57 to 0.38 and 0.37 in 3.5 wt% NaCl electrolyte. The lower friction coefficient of the Cr/CrN multilayer nanostructured coating is perhaps due to its higher hardness and lower roughness.

Influence of the Addition of the Elements Ti and Cr on the Structure, and Mechanical and Tribological Properties of AlSiN Coatings

The influence of Al/Ti and Al/Cr ratios on the structural, mechanical and tribological properties of AlTiSiN and AlCrSiN coatings, deposited by the cathodic arc evaporation PVD method at a temperature of 400°C, was investigated. The remains of the original AlSiN hexagonal phase were observed in the obtained coatings as well as the crystallites of cubic TiN and CrN, respectively. XPS analysis assumes the presence of a substoichiometric SiN. The addition of 11 at.% Ti or 13 at.% Cr in AlSiN led to an increase in both the coating’s resistance to plastic deformation and the plasticity index. The addition of 13 at.% and 24 at.% Cr to the AlSiN coating structure resulted in a decrease in the average coefficient of friction with 18% and 36% against a counterpart of Al2O3, respectively, and with 36% for both concentration against steel ball counterpart. The addition of Ti have no influence on the values of the coefficient of friction at using ceramic counterpart, while at steel counterpart decreased it up to 30%. Both element change the abrasion effect of the coating.Keywords:AlCrSiN; AlTiSiN;Cathodic Arc Deposition; Tribological Behaviour; Abrasion Resistance; Nanoindentation

Performance evaluation of HiPIMS, S3p and CAE deposited coatings during dry turning of Dss2205

The present study is an extension of our previous work. Performance evaluation of single-layer AlTiN coating deposited by Scalable Pulse Power Plasma (S3p) and High Power Impulse Magnetron Sputtering (HiPIMS), with multi-layer TiN/TiAlN and AlTiN/TiAlN coating deposited by Cathodic Arc Evaporation (CAE) is carried out. Taguchi’s full factorial design with L9 orthogonal array was used for machining. AlTiN (S3p) coating exhibited a tool life of 111 min, 1.5 times as much as AlTiN (HiPIMS) coating. Multi-layer coatings could not offer comparable performance with single-layer coatings. Among the multi-layer coatings’ tools having the top layer of Al performed better. Surface roughness exhibited by AlTiN (S3p) tool was 1.2 µm compared to 1.8 µm by AlTiN (HiPIMS) tools. The rate of reduction of cutting force for AlTiN (HiPIMS) and AlTiN (S3p) tools was found to be 5% and 11%, respectively. Multi-layer TiN/TiAlN-coated tool exhibited 2.5 times higher surface roughness compared to single-layer AlTiCrN coated tool. Empirical models showed predictability of 5% and 20% for cutting force and surface roughness respectively. The higher predictability range for surface roughness is due to influence of both cutting speed and feed. The developed models can be used for selection among AlTiN (S3p) and AlTiN (HiPIMS) coated tools.

Electrochemical and biological properties of mono- and bilayer nitride coatings deposited on Ti–6%Al–4%V alloy

Mono- and bilayer coatings were deposited by plasma nitriding process, cathodic plasma electrolytic deposition, and cathodic arc evaporation methods to improve the corrosion resistance and biological properties of the Ti–6Al–4V substrate. Coatings characterizations include phase analysis, surface morphology, and film microstructure observations were done using X-ray diffraction (XRD) analysis, atomic force microscope, and field emission scanning electron microscopy (FESEM), respectively. The results confirmed the formation of titanium nitride phases (TiN and Ti2N) in plasma nitriding and cathodic arc evaporation processes and deposition of oxy-nitride phases (TiNxOy) in plasma electrolytic nitriding process. The electrochemical study of coated and uncoated samples in a simulated body fluid (SBF) solution revealed the lower corrosion current density for bilayer nitride coating in comparison to the monolayer coating and substrate. Lower penetration of solution and more stable phases such as TiO2 improved the corrosion resistance of bilayer coatings. Hemocompatibility and MTT assay were performed on the coated and uncoated sample to determine the blood compatibility and cell viability. The statistical results showed better cell growth on the bilayer nitride coatings after three days.

Comparison of electrochemical behavior of CrN single‐layer coating and Cr/CrN nanolayered coating produced by cathodic arc evaporation physical vapor deposition

AbstractThe aim of the present work is to study the CrN single‐layer coating and the Cr/CrN nanolayered coating by cathodic arc evaporation physical vapor deposition (CAE‐PVD) on AISI 304 stainless steel and to assess the electrochemical behavior of the coatings. Field emission scanning electron microscopy (FE‐SEM) and X‐ray diffraction (XRD) were utilized to study the morphology and microstructure of the coatings. The mechanical behavior of the coatings was studied by the nanoindentation technique. The electrochemical behavior of the formed coatings in 3.5 wt.% NaCl solution was investigated via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests. Based on the microscopic images, it was realized that both CrN and Cr/CrN coatings were formed having a dense structure on the substrate. The results of EIS measurements showed gradual changes in the polarization resistance of the Cr/CrN nanolayered coating during the immersion time. However, significant changes in the polarization resistance of the CrN single‐layer coating were seen by increasing immersion time comparing with the Cr/CrN coating. The higher polarization resistance of the Cr/CrN coating can be attributed to the effects of the interface between the layers in comparison to the CrN coating.

Tribological properties of in-situ PVD TiAlN, TiSiN, and TiAlN/TiSiN coatings under ambient air and vacuum environment

It is known that the interest in manufacturing in a vacuum environment has increased in recent years. Thus, the wear behavior of mechanical tools under vacuum conditions has critical importance. However, adhesion and cold-welding problems between tool and working piece in vacuum conditions lead to poor wear properties and severe coefficient of friction values. Surface treatment methods such as physical vapor deposition coatings can eliminate these undesirable consequences, especially transition metal nitrides. In this study, TiAlN, TiSiN, and TiAlN/TiSiN films were coated on AISI H13 tool steels employing the cathodic arc evaporation technique. Whether the coatings grown to the substrate surface have a positive contribution to the wear performance of the substrate in the ambient air and vacuum environment was answered. Scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer analyses were used to attain structural properties. The hardness was measured using a nano-hardness tester, and the adhesion properties were determined by a scratch test. The wear behavior of the substrate and coating samples are determined under 2 N constant normal load and using WC-6%Co counter bodies under ambient air and vacuum conditions. The hardness of samples improved owing to surface coatings, and the highest nano-hardness value was determined from the TiSiN coatings as 39.42 GPa, which is ∼700% greater than the substrate. It has been observed that coated samples have superior wear performance in both wear conditions. Besides, it is determined that those tested under a vacuum condition showed superior wear resistance than the samples tested under ambient air. While TiSiN film exhibits the highest wear resistance in ambient air, the TiAlN/TiSiN layer is the best in a vacuum environment. Owing to the deposited coatings, the seizure mechanism between the friction surfaces, which is frequently encountered in the vacuum environment, is prevented, and a fascinating improvement in terms of friction coefficient is achieved.

Comparative analysis of cavitation erosion of Cr-C carbide coatings depending on the carbon content

The aim of the study was to conduct a comparative analysis of the cavitation erosion resistance of thick (up to 20 μm) Cr-C coatings by means of the rotating-disk testing method. An experimental study was carried out of the process of cavitation destruction of Cr18Ni10Ti stainless steel samples with Cr-C thick coatings depending on the carbon concentration in the coating. Nanocrystalline thick coatings of Cr-C were deposited by using the cathodic arc evaporation (Arc PVD) method. The results showed that the erosion rate of the coated samples was more than four times less than that of the uncoated sample. The Cr-C samples coated with 28.8 at % carbon content demonstrated less surface damage compared to the other coated samples and the reference samples.

On the preferred orientation in Ti1–x Al x N and Ti1–x–y Al x Si y N thin films

Abstract The influence of the deposition geometry and the chemical composition on the form and degree of the preferred orientation of crystallites was investigated in TiN, Ti1–x Al x N, and Ti1–x–y Al x Si y N thin films deposited by cathodic arc evaporation. The deposition geometry was varied by changing the angle between the cathodes and the substrates. The chemical composition of the thin films was modified by the choice of the cathodic materials. In TiN thin films, the crystallites were preferentially oriented with the {111} direction perpendicular to the sample surface, independent of the deposition geometry. Besides, a well-pronounced in-plane texture was observed. Co-deposition of Ti, Al, and Si in nitrogen atmosphere stimulated inclination of the texture direction towards the sample surface, which can be described as a change of the texture direction related to the sample surface perpendicular direction, and reduced the amount of the in-plane texture in the coatings (the preferred orientation of crystallites in the plane of the coating).

Hybrid magnetron sputtering of ceramic superlattices for application in a next generation of combustion engines

A hybrid magnetron sputtering process (dcMS/HiPIMS) was developed to manufacture nanostructured CrN/Cr1-xAlxN multilayers, motivated by improving the low-emission efficiency when applied on gas-nitrided diesel piston rings of a next-generation of combustion engines. In order to improve the mechanical, tribological, and corrosion behavior of the multilayers, the hybrid dcMS/HiPIMS process was designed by selecting the optimal sputtering procedure applied to AISI 440 base steel. The effect of substrate bias and carousel rotational speed on the phase composition, crystallographic texture, residual stresses, surface roughness, coating periodicity and densification, instrumented hardness, elastic modulus, as well as wear and corrosion resistance was determined. The results have demonstrated that hybrid magnetron sputtering produces multilayers with a superlattice structure, which outperforms commercial PVD coatings of CrN for diesel piston rings manufactured by cathodic arc evaporation. Also, multilayer periodicities in the range of 5 to 10 nm yield the best tribological performance under bench tests for the piston ring/cylinder liner system.

Mechanical properties and high temperature oxidation resistance of (AlCrTiV)N coatings synthesized by cathodic arc deposition

High entropy alloy nitrides (AlCrTiV)N coatings were deposited by cathodic arc evaporation at various deposition bias and temperature. The mechanical properties of the as-deposited coatings and their oxidation resistance after annealing at various temperatures were analysed. X-ray analyses show in all coatings a FCC structure with a (111) preferred orientation up to 750 °C. Up to 600 °C, no oxygen penetration is measured in the films while at 800 °C, critical spalling occurs for all samples. The coating deposited at a temperature of 300 °C and negative bias of 100 V exhibits the most interesting compromise in both oxidation resistance and mechanical performances with a hardness of 40 GPa, a friction coefficient of 0.44 and a wear rate of 5.8 · 10−7 mm3·N−1·m−1. Annealing in air at 600 °C for 2h reduces the wear rate to 2.1 · 10−7 mm3·N−1·m−1 and the surface hardness to 17 GPa. Although annealing forms a thin oxide layer that reduces the hardness on the surface of the coating, it also averages the hardness inside the film to 33 GPa regardless of the deposition bias.

Influence of post-deposition annealing temperature on morphological, mechanical and electrochemical properties of CrN/CrAlN multilayer coating deposited by cathodic arc evaporation- physical vapor deposition process

CrN/CrAlN multilayer coatings were deposited on AISI 304 stainless steel substrates utilizing the CAE-PVD process. Then the coatings were annealed at 400, 500, 600, and 700 °C for a duration of 1 h in a vacuum condition. The phases identification, surface morphology, mechanical properties, adhesion, and corrosion behavior of the coating before and after post-deposition annealing treatment were characterized using XRD, SEM, nanoindentation test, Rockwell-C adhesion measurements, and EIS assays, respectively. The results indicated that with increasing post-deposition annealing treatment temperature, the phase structures of the multilayer coating vary from a face-centered cubic CrN to a hexagonal Cr 2 N. Moreover, annealing resulted, in the decrease of the macroparticles on the coating surface decreased. The hardness of the multilayer coating decreased from 19 GPa to 17 GPa, which can be ascribed to the increase in crystallite size and the decrease in the residual stress and annihilation of defects as the temperature increased to 700 °C. Based on the EIS results, the sample annealed at 700 °C had the highest corrosion resistance among other samples, which can be attributed to a decrease in the porosities as corrosion initiation sites, the existence of Cr 2 N as corrosion resistance phase, and an increase in the crystallite size of the multilayer coating. • Comprehensive evaluation on the effect of annealing on CrN/CrAlN multilayer coating. • Significant decrease in residual stress and macrostrain. • Crystallite growth resulted in the decrease in the hardness of the coating by 10%. • Enhancement of electrochemical properties through post-deposition annealing.

Microstructural and micro-mechanical investigation of cathodic arc evaporated ZrN/TiN multilayer coatings with varying bilayer thickness

Modifying the architecture of multilayer hard coatings allows to adjust the mechanical properties of these materials for a given application. Within this work, the effect of the bilayer thickness (Λ) and the individual sublayer thickness ratio on the microstructure and mechanical properties of ZrN/TiN multilayer coatings was investigated. Multilayer coatings with Λ of 570, 320 and 35 nm were deposited by cathodic arc evaporation and compared to TiN and ZrN single-layer coatings. The microstructure was investigated by X-ray diffraction (XRD) and scanning electron microscopy. All coatings exhibit a single phase face-centred cubic structure and a predominant (111) texture. A columnar structure was observed for all coatings and grain growth extending beyond the ZrN/TiN interfaces was evident in all multilayers. For all coatings, compressive residual stresses were determined by XRD using the sin 2 ψ method, where the multilayer sample with the largest Λ exhibited the highest compressive residual stress of −1.7 ± 0.2 GPa. Lower compressive residual stresses could be correlated with decreasing Λ and decreasing ZrN:TiN thickness ratio. Nanoindentation experiments as well as micro-mechanical bending tests were conducted to assess the mechanical properties of the coatings. The ZrN/TiN multilayer sample with Λ of 35 nm showed the highest hardness of 28.0 ± 1.1 GPa. This value is similar to the TiN single-layer and higher compared to the ZrN single-layer, which exhibited a hardness of 27.9 ± 1.4 GPa and 25.8 ± 1.3 GPa, respectively. While the ZrN single-layer showed the highest fracture toughness, the ZrN/TiN multilayer samples were identified as the mechanically stiffest and strongest of the investigated coatings, since they exhibited a higher fracture stress compared to the single-layer coatings. The obtained results allow to optimise the architecture of ZrN/TiN multilayer coatings yielding the desired coating properties for application in the cutting industry. • Arc evaporated ZrN/TiN multilayer coatings with varying bilayer thickness Λ • Smaller Λ leads to grain refinement and more pronounced (111) texture. • Multilayer coating with lowest Λ exhibits the highest hardness. • Highest fracture toughness for ZrN single-layer coating • Improved fracture stress for multilayers compared to single-layers

Influence of oxygen content on structure, thermal stability, oxidation resistance, and corrosion resistance of arc evaporated (Cr, Al)N coatings

(CrxAl1-x)(OyN1-y)ε coatings with different oxygen fractions were prepared by cathodic arc evaporation through variation of injected oxygen flux, and elaborated concerning structure, mechanical properties, thermal stability, oxidation resistance, and electrochemical properties. A moderate addition of O into (Cr, Al)N coatings generates a (Cr, Al)(O, N) solid solution with a face-centered cubic structure, whereas an additional corundum-structured (Cr, Al)2O3 solid solution is formed with superfluous oxygen introduced. The addition of O effectively improves the thermal stability by retarding the formation of w-AlN as well as the dissociation of the CrN bond, allowing the oxynitride coatings to maintain higher hardness after annealing. Notably, a small fraction of O-addition (e.g. 8 or 21 at.% in non-metal sublattice) enhances significantly the resistance against oxidation to above 1100 °C by facilitating the formation of a protective Al-rich oxide scale. Further incorporation of O gives rise to a development of oxide scale with unity elemental distribution and hence results in inferior oxidation resistance. Nevertheless, the O-rich oxynitride coatings provide better protection against electrochemical corrosion while the N-rich coatings exhibit higher corrosion current as well as lower polarization resistance compared to the CrAlN coating.

Influence of preliminary metal-ion etching on the topography and mechanical behavior of TiAlN coatings on cemented carbides

Metal-ion etching is widely used in substrate surface modification before coating by physical vapor deposition . In this work, TiAlN coatings were synthesized onto cemented carbides with Ti-, Cr-, and Zr-ion pre-etching by cathodic arc evaporation and investigated concerning surface topography and mechanical failure. The pre-etching of energetic metal ions introduces droplet defects and increases surface roughness through uneven bombardment. The high interface roughness and deposition of nanoscale metal interlayers contributed to the upgraded adhesion between the coating and the substrate. As a result, the adhesion strength of TiAlN coatings advances to more than 95 N by applying Cr- and Zr-ion pre-etching. The rough substrate surface also gives rise to a rough coating surface associated with the pre-etching time. Under normal loading, the microscopic pit-like surface morphology , stemming from ion etching, interrupts the transverse propagation of the circumferential cracks but does not affect the longitudinal crack propagation inside the coating. In addition, the higher roughness of coatings with ion pre-etching causes a shorter run-in stage during ball-on-disc tests due to the higher contact stress between the friction pair. • TiAlN coatings were deposited on cemented carbide with various ion pre-etching. • The ion etching changes the substrate surface, significantly increasing roughness. • Scratch adhesion strength above 95 N can be obtained by suitable ion pre-etching. • Rough surfaces lead to intermitted circumferential cracks under normal loading. • The ion pre-etching can also shorten the run-in period during friction tests.

Microstructure, oxidation behavior and tribological properties of AlCrN/Cu coatings deposited by a hybrid PVD technique

• AlCrN/Cu coatings were deposited combining cathodic arc evaporation and magnetron sputtering. • Epitaxial growth of Cu sublayers on AlCrN achieves a hardness greater than 30 GPa. • Excessive Cu-incorporation causes the disintegration of the multilayered structure. • Temperate CuO oxide with fine grain size contributes to decreased friction coefficients. • Severe oxidation related to Cu-content leads to inferior tribological properties. Achieving high hardness and low friction at elevated temperatures for nitride-based hard coatings has substantial scientific interest and application significance. In this study, AlCrN/Cu coatings were deposited by a hybrid PVD technique combining arc evaporation from an Al 60 Cr 40 target and magnetron sputtering from a Cu target in a mixed Ar and N 2 atmosphere. The microstructure, oxidation behavior, and tribological properties of the coatings were investigated. AlCrN/Cu coatings show a dual-phase structure of (Al, Cr)N solid solution and Cu metallic phase. Excessive sputtering power of the Cu target induces the disintegration of interlayer interfaces of the nano-multilayered geometry, accompanied by a decline in hardness from above 30 GPa to 22.7 GPa. Moreover, the formation of fine CuO grains on the coating surface is conducive to reducing the friction coefficient of AlCrN/Cu when exposed to air at high temperatures. The AlCrN/Cu coating with a sputtering power of 0.5 kW obtains a friction coefficient of 0.39 ± 0.05 after pre-oxidation at 800 °C, distinctly lower than that of AlCrN, which exhibits a friction coefficient of ∼0.65. The further transformation of CuO to cubic Cu(Al, Cr) 2 O 4 , which stems from the solid-state reaction of CuO, Al 2 O 3 , and Cr 2 O 3 , would cause a rise in friction coefficient and wear loss. The mechanism of oxidation and tribological behavior of the AlCrN/Cu coatings related to the temperature and Cu content was discussed.