AlCrN Films Research Articles

Comparative investigation of the structure and mechanical properties of AlCrN and AlCrVYN thin films deposited by dcMS, HiPIMS, and hybrid dcMS/HiPIMS

AlCrN and AlCrVYN thin films were deposited by physical vapor deposition using dcMS, HiPIMS and hybrid dcMS/HiPIMS processes. Although all the thin films were produced using the same time-average power and show only slight differences in the chemical composition, significant differences regarding their structure, morphology, and mechanical properties were identified. Both dcMS-AlCrN and dcMS-AlCrVYN thin films show a column-like structure of sharply defined grains with large crystallites having size of 168 nm and 133 nm and exhibit a low hardness of (6.7 ± 1.3) GPa and (8.9 ± 1.0) GPa, respectively. In contrast, HiPIMS thin films, despite their lower deposition rate (especially evident in HiPIMS-AlCrVYN, which exhibited the lowest deposition rate among all examined films), show a denser structure predominantly composed of fcc-CrN and, in the case of HiPIMS- and dcMS/HiPIMS-AlCrN, small amounts of hcp-AlN. Consequently, the HiPIMS-AlCrN and HiPIMS-AlCrVYN thin films showed higher hardness values of 28.0 ± 2.1 GPa and 30.7 ± 1.9 GPa, respectively. Combining the two methods by using one cathode in dcMS mode and one in HiPIMS mode results in films with similar hardness values (26.9 ± 1.6 GPa for AlCrN and 28.7 ± 2.2 GPa for AlCrVYN) and morphologies comparable to the pure HiPIMS thin films, but with an increase in the deposition rate. This demonstrates the advantage of combining the two methods, especially for the AlCrVYN thin film production. In comparison to AlCrN, the AlCrVYN thin films generally exhibit higher hardness demonstrating the advantage of adding larger atoms into the thin film structure.

Diamond-Like Carbon (DLC) and AlCrN films onto Ti-6Al-4V substrates by Laser-Powder Bed Fusion (L-PBF): Effect of substrate heat treatment and surface finish

This paper focuses on the performance of thin-film coatings onto additively manufactured Ti-6Al-4V. Specifically, because metal parts obtained by laser-powder bed fusion (L-PBF) often require post-process heat treatments and surface finishing to meet end-user specifications, we studied how the resulting changes to mechanical strength and surface roughness affect the performance of films deposited by physical or plasma-enhanced chemical vapor deposition (PVD, PE-CVD). L-PBF Ti-6Al-4V substrates were heat-treated either below or above the β-transus and finished by grinding with different grit sizes, and then were coated with PVD AlCrN or a PE-CVD DLC-based film.Scratch adhesion on harder surfaces treated below the β-transus was higher with both coating types, whilst the substrate finishing had a negligible effect. Conversely, in ball-on-disc sliding wear tests, substrate roughness had a dominant effect: rough surfaces always resulted in earlier cracking and delamination of the coatings. Substrate hardness had a minor effect only with the AlCrN film. Moreover, the DLC-based films, because of the low-friction conditions they establish through a graphitized tribofilm as well as their higher H/E ratio, survived severe contact conditions better than the stiffer AlCrN. The results were interpreted in the light of the plasticity indices of the coated systems and their tribochemical interactions.

Post-deposition annealing effects on microstructure, mechanical and tribological properties of AlCrN films

The post-deposition annealing of AlCrN films was conducted in an atmospheric environment for 2 h, with annealing temperatures ranging from 25 to 1000 °C. The microstructure, mechanical, and tribological properties were systematically investigated as a function of the annealing temperature. The results show that the AlN phase in the film began to oxidize at 600 °C, resulting in deterioration of the film's toughness and resistance to plastic deformation. Subsequently, the wear resistance also deteriorated, with the wear rate being nearly 16 times that of the as-deposited film. At 800 °C, the AlN obviously underwent oxidization to form Al2O3. The high temperature annealing promoted the coalescence of Cr on the film surface and caused a reaction with the Al2O3 to form a replacement solid solution of Cr–O–Al, thereby improving the mechanical properties of the annealed films. At the same time, the tribological properties of the films were not significantly deteriorated by annealing at temperatures other than 600 °C, similar to those of the films without any annealing treatment.

Revealing dynamic-mechanical properties of precipitates in a nanostructured thin film using micromechanical spectroscopy

Abstract Nanostructured materials with their remarkable properties are key enablers in many modern applications. For example, industrial dry-milling processes would not be as widely spread without the use of hard, wear-resistant metal nitride coatings to protect the cutting tools. However, improving these nanostructured thin films with regard to dynamical properties is demanding as probing respective parameters of (sub-)micron layers without any substrate influence is still challenging. To extend the scientific toolbox for such spatially confined systems, a novel methodological approach based on resonance peak measurements of a cantilever-transducer system termed micromechanical spectroscopy (µMS) is developed and applied to a Al0.8Cr0.2N model system. The mainly wurtzite type supersaturated Al0.8Cr0.2N system showed precipitation of cubic CrN at grain boundaries and local Cr variations upon annealing at 1050°C. This was accompanied by an increase in the previously unknown damping capability of 63 percent and an increase in Young’s modulus by 36 percent. Impact statement There is a wide variety of applications for nano- to micrometer-sized thin films in today’s engineering technology, from thermal barrier- and wear-resistant coatings in turbines and bearings, over diffusion barriers and heatsinks in microelectronic devices, to optically active layers in lasers or mirrors. The mechanical properties of such thin films are oftentimes governed by their thermal history, leading to either intentional or undesired changes in the microstructure (e.g., the formation of precipitates). While the investigation of such features is usually constricted to static analysis using high-resolution techniques, such as transmission electron microscopy, understanding their impact on dynamic properties of the film remains a challenge. However, these are highly relevant in many engineering applications where cyclic behavior is common, such as high-speed dry milling. In the present work, we investigate the change in mechanical damping capability upon annealing of a 6-µm thin AlCrN film, commonly used in demanding dry-milling applications, using micromechanical spectroscopy (µMS) of cantilever-shaped specimens. After a carefully adjusted heat treatment, the film exhibits the formation of cubic CrN precipitates in an otherwise wurtzite AlCrN matrix, which leads to a previously unknown beneficial increase in damping capability of the film. Graphical abstract

Effects of Carbon Doping and DC Bias Voltage on Microstructure and Mechanical Properties of AlCrCN Films Synthesized via HiPIMS.

This work compares the hardness and adhesion properties of AlCrN and AlCrCN hard coatings synthesized via HiPIMS using Al70Cr30 and Cr targets. The hardness and adhesion properties of AlCrCN films were optimized by performing deposition under various C2H2 flow rates (5, 8, 10, 13, 15, or 20 sccm) and DC bias voltages (−40, −60, −80, −100, or −120 V). EPMA results clearly indicated that the carbon content was increased from 1.9 to 12.2 at.% with increasing C2H2 flow rate from 5 to 20 sccm. XPS results confirmed a various content of chemical bonds (Cr-N, C-N, sp2, and sp3) with various C2H2 flow rate. Grain and columnar refinement in AlCrCN were derived from XRD, TEM, and SAED results. The higher hardness (28.6 GPa) and Young’s modulus (358 GPa) were obtained using an C2H2 flow rate of 5 sccm and a bias voltage of −60 V. Both of which subsequently decreased to 13.5 GPa and 212 GPa, respectively. This can be attributed to the C-N bond inhibiting the development of metal-N bonds. Increasing the bias voltage to −120 V increased the hardness to 32.9 GPa and the Young’s modulus to 372 GPa. Note that the application of bias voltage to enhance hardness should also be applicable to carbon-doped AlCrN films as well. All samples presented good adhesion characteristics (class 1; ISO26443:2008-06).

AlCrN/Cr3C2–NiCr duplex coating towards high load-bearing and dry sliding antiwear applications

In this study, experimental analysis and finite element modeling (FEM) were employed to investigate the microstructure and mechanical properties of duplex coatings composed of a Cr3C2–NiCr interlayer and a top AlCrN film in comparison with these of a single AlCrN film. Results showed a significant improvement in the adhesive strength, load-bearing capacity, H/E, and H3/E2 ratios, and hardness of the AlCrN/Cr3C2–NiCr duplex coatings compared to the single AlCrN film, especially the wear resistance that increased by nearly eight times under heavy loads. Moreover, FEM analysis revealed that the duplex design reduced the stress concentration area on the surface of AlCrN film and kept it far away from the contact interface during load-bearing.

Tribological and mechanical properties of AlCrBN hard coating deposited using cathodic arc evaporation

Transition metal nitride coatings, such as CrN, AlCrN and AlTiN, have excellent mechanical properties such as high strength, hardness, wear resistance and thermal stability. In this study, AlCrN and AlCrBN thin films were deposited by cathodic arc evaporation (CAE) using binary AlCr and ternary AlCrB alloy targets. The adhesion strength of the films to the substrate was effectively improved using composition-gradient interlayers. To study the thermal stabilities, the AlCrN and AlCrBN coatings were annealed at high temperature up to 900 °C, and their oxidation resistance, mechanical properties and thermal stabilities were studied. AlCrN and AlCrBN coated WC-Co samples were tested using pin-on-disk wear test configuration to evaluate the tribological performance. According to experimental results, the AlCrBN is composed of a face-centered cubic B1 (FCC) nanocrystalline structure, which can effectively inhibit the growth of grains, resulting in formation of a compact structure of grain refinement, and hinder the plastic deformation, thus obtaining high hardness and excellent wear resistance. The addition of 0.6 at.% B into the AlCrN decreased the grain size to 8.7 ± 0.8 nm from 13.7 ± 1.1 nm of AlCrN. Due to the addition of B element, the grains of AlCrBN coatings were refined to form a compact structure. Oxygen (O) did not penetrate and oxidize easily along the grain boundaries during annealing at high temperature. In addition, the AlCrBN coatings maintained a certain hardness (27.9–30 GPa) after high temperature oxidation, and the AlCrBN coating after annealing at 900 °C had the lowest wear rate (1.25 × 10−7 mm3/Nm). The AlCrBN coating annealed at high temperature still possessed predominant tribological properties, excellent thermal stability and good adhesion. This study demonstrates the feasibility of improving the life and performance of WC-Co tools by the application of cathodic arc deposited AlCrBN coatings using ternary AlCrB alloy targets.

Adhesion and machining performance of PVD AlCrN coatings with an ion beam/laser textured substrate

The insufficient adhesive strength of Physical Vapor Deposition (PVD) coatings is still the key issue that needs to be solved urgently for high-efficiency and high-quality difficult-to-machine materials cutting processing. Currently, laser micromachining is extensively utilized to fabricate micro-textures on the substrate to enhance coatings adhesion. However, laser ablation will cause irregular protrusions inside and on the edges of the textures, which could influence the quality of deposited coatings. Therefore, micro-textures were fabricated on the substrate by an ion beam (IBE)/laser machining method, and the influence of IBE/laser textures on the adhesive strength of PVD coatings is revealed. Firstly, a micro-pits array was prepared on WC/Co substrates with different machining parameters, such as laser repetition frequency and ion beam etching time. The micro-topography and mechanical properties of the substrates with different pretreatments were studied. Then, cathode arc-evaporation technique was utilized to deposit AlCrN film on the IBE/laser textured substrates. The scratch test and dry machining experiments of AISI 316 L stainless steel were performed to evaluate the adhesive strength and machining performance of the coated samples with various pretreated substrates. The results demonstrate that laser texturing and ion beam etching both enhanced the coatings adhesion. Therefore, the critical load of the coatings deposited on the IBE/laser textured substrates with 25 kHz laser repetition frequency and 150 min etching time (F N, C2 = 3.39 N) exhibited the highest value, which was 19.4% higher than that of the conventional AlCrN samples (F N, C2 = 2.84 N). Moreover, the cutting forces F X , F Y , F Z and the friction coefficient of IBE/laser textured coated tool were decreased by 18.7%, 20.6%, 10.2% and 16.7% compared with that of conventional coated tool at the high cutting speed of 200 m/min. Finally, the possible mechanisms of IBE/laser texturing pretreatment on enhancing PVD coatings adhesion were discussed. • A micro-pits array is fabricated by an ion beam (IBE)/laser machining method. • Effect of ion beam (IBE)/laser textures on adhesion of PVD coatings is studied. • Mechanism of IBE/laser texturing to improve coatings adhesion is revealed.

Lubricated sliding of CFRPEEK/AlCrN film tribo-pair and its effect on the mechanical properties and structural integrity of the AlCrN film

The tribological behavior of AlCrN film against carbon-reinforced PEEK (CFRPEEK) was investigated using pin-on-disc tribometer in simulated body fluid (SBF) lubrication. The materials were characterized using XRD, AFM, Raman spectroscopy, nanoindentation and nanoscratch tests to understand their structural make-up and mechanical behavior. Post tribotests, the worn coated surface was further analyzed using nanoindentation test, nanoscratch test and Raman spectroscopy to evaluate the effect of the lubricated sliding on the structural integrity and mechanical properties of the AlCrN film. Findings showed that the AlCrN film was composed of dominant cubic CrN structure while CFRPEEK registered intensity peak in XRD attributed to carbon introduction in the PEEK matrix. The p-h plot indicated elastoplastic nature of the AlCrN film inducing high hardness and elastic modulus while CFRPEEK had suffered significant plastic deformation. In simulated tribotest, the AlCrN film witnessed mild abrasion whereas CFRPEEK showcased deformation and fracture induced tearing and fiber pull-out. What is more, the worn AlCrN surface retained its compositional integrity and preserved its indentation hardness, scratch hardness, elastic modulus and H/E attribute as suggestive from the one-way ANOVA test with Tukey's grouping.

Modeling of wear parameters and multi-criteria optimization by Box-Behnken design of AlCrN thin film against gamma-irradiated Ti6Al4V counterbody

AlCrN film deposited on medical grade 316 LVM stainless steel was subjected to wear test against gamma-irradiated Ti6Al4V counterbody. In this tribological study, a statistical model was employed using Response surface methodology (RSM) based Box-Behnken design (BBD) to optimize and evaluate the individual and interactive effect of the three independent design parameters, namely applied load, sliding velocity, and sliding distance on the wear responses such as surface roughness, friction coefficient, disc mass loss, wear depth and hardness. The RSM was in good agreement with higher R2 and predicted R2 value for all the wear responses. The ANOVA and interactive contour maps clearly manifest the individual and relative effect of the design parameters on the wear responses suggesting a significant effect of sliding velocity and applied load on surface roughness, friction coefficient, and hardness and an important role of applied load on disc mass loss and wear depth. The worn surface analysis using SEM (with EDS) and XRD was also discussed, evincing the formation of relevant oxides on the interfacial tribolayer of the worn surface resulting in a lower friction coefficient, thus contributing to inhibition of severe wear mass loss of the AlCrN film. The wear debris originated from the dry sliding showcased the characteristics of the typical fatigue wear particle with irregular and sharp periphery.

Effects of nitrogen-argon flow ratio on the microstructural and mechanical properties of AlCrN coatings prepared using high power impulse magnetron sputtering

In this study, AlCrN films were deposited from Al70Cr30 alloy targets by high-power impulse magnetron sputtering (HiPIMS). The structural characteristics of the AlCrN films were modulated by performing deposition under various N2/Ar flow ratios. The results indicated that increasing the nitrogen content during deposition leads to corresponding decreases in deposition rate and film thickness, as well as a structural transformation from amorphous to crystalline. A mixture of cubic and hexagonal AlCrN phases was found in the films. Three regions of hardness were observed, and hardness increased with increasing N2/Ar ratio and peaked at 33.6GPa. Good adhesion and wear resistance were observed in all samples.

Milling characteristics of VN/AlCrN-multilayer PVD coated tools with lubricity and heat resistance

The mechanical and tribological characteristics of the VN/AlCrN multilayered coating films are investigated for cutting tools by using the arc ion plating (AIP) method with a rectilinear magnetic filtering system. The VN coating film forms vanadium oxide VxO1–x that has low friction coefficient on a surface above 500°C, whereas AlCrN coatings exhibit higher hot hardness and oxidation resistance. Therefore, the VN/AlCrN multilayer coatings are expected to demonstrate both superior lubricity and heat resistance, whose characteristics depend mostly on the combination of VN and AlCrN films. Moreover, some lower cutting force, tool wear, and tool flank temperature are obtained at high speed end milling of a prehardened stainless steel, as expected.

Stress-controlled decomposition routes in cubic AlCrN films assessed by in-situ high-temperature high-energy grazing incidence transmission X-ray diffraction

The dependence of decomposition routes on intrinsic microstructure and stress in nanocrystalline transition metal nitrides is not yet fully understood. In this contribution, three Al0.7Cr0.3N thin films with residual stress magnitudes of −3510, −4660 and −5930 MPa in the as-deposited state were in-situ characterized in the range of 25–1100 °C using in-situ synchrotron high-temperature high-energy grazing-incidence-transmission X-ray diffraction and temperature evolutions of phases, coefficients of thermal expansion, structural defects, texture as well as residual, thermal and intrinsic stresses were evaluated. The multi-parameter experimental data indicate a complex intrinsic stress and phase changes governed by a microstructure recovery and phase transformations taking place above the deposition temperature. Though the decomposition temperatures of metastable cubic Al0.7Cr0.3N phase in the range of 698–914 °C are inversely proportional to the magnitudes of deposition temperatures, the decomposition process itself starts at the same stress level of ~−4300 MPa in all three films. This phenomenon indicates that the particular compressive stress level functions as an energy threshold at which the diffusion driven formation of hexagonal Al(Cr)N phase is initiated, provided sufficient temperature is applied. In summary, the unique synchrotron experimental setup indicated that residual stresses play a decisive role in the decomposition routes of nanocrystalline transition metal nitrides.

Structure and tribological properties of DLC:Si/AlCrN low friction thin film

A wide range of diamond-like carbon coatings is caused by their structure composed of sp2and sp3carbon hybridisation and the possibility of both metallic and non-metallic admixtures or the creation of a hydrogenated form. One of the ways to improve the tribological properties of DLC is to dope it with silicon. Deposited on stainless steel substrate coating system composed of AlCrN film covered by DLC:Si was the subject of the studies. The AlCrN and DLC:Si layers were deposited by PVD lateral rotating ARC-cathodes and PACVD on the X6CrNiMoTi17-12-2 steel respectively. Characteristics of DLC:Si film was performed by imaging the topography using SEM and AFM. The structure was investigated using a Raman spectroscopy and HRTEM. Tribological and adhesion tests were carried out using a ball-on-disc and a scratch test respectively. Tests using the TEM confirmed an amorphous character of DLC:Si layer. A phase composition analysis of the DLC:Si layer with the Raman spectroscopy method showed the presence of bonds distinctive for diamond (sp3) and graphite (sp2), typically observed in DLC coatings. Under the technically dry friction conditions, the friction coefficient for the associations tested is within the range 0.14 for the investigated coating.

The wear performance of carbide tools coated with TiAlSiN, AlCrN and TiAlN ceramic films in intelligent machining process

Nitride-based coatings are applied by cathodic arc physical vapor deposition (CAPVD) to improve the tribological properties of cutting tools. The present study examines the tool life of carbide tools coated with TiAlSiN, AlCrN and TiAlN films in intelligent machining process. Coating process was applied on both prismatic carbide test specimens and solid carbide end mills. Coating characterization was carried out on the test specimens. The structural, mechanical and tribological properties of different nitride-based coatings were investigated by means of field emission scanning electron microscope (FEG-SEM), X-ray diffractometer (XRD), scratch tester, reciprocating tribometer, calotester, microhardness device and optical profilometer. Impax steel was machined in CNC vertical machining center with uncoated and coated carbide end mills in order to determine the actual operating performance of the coatings. The g codes and toolpaths were created in the SolidCAM iMachining software. The cutting speed, feeds and overlap values are selected automatically and variably depending on geometry, tool and workpiece materials. The flank wear widths of tools were determined by SEM. In addition, the surface roughness values of the impax steel were measured from the finish surfaces. According to the scratch test results, the best adhesion results were obtained for TiAlN coating and the Lc1 critical load value was determined as about 30 N. The reciprocating sliding test results showed that the highest wear rate was obtained for the TiAlSiN coated specimen and the lowest wear rate was obtained for the uncoated specimen. Flank wear was observed on the tools after the milling process and the highest wear resistance was obtained TiAlN coated end mill. The lowest surface roughness value was obtained from the surface of impax steel workpiece which was milled with carbide end mill coated with TiAlN ceramic film.

Separation of tungsten and cobalt from WC-Co hard metal wastes using ion-exchange and solvent extraction with ionic liquid

Recently, the development of a process to separate W and Co from tungsten carbide-cobalt (WC-Co) hard metal wastes has become important. In this study, we proposed a novel hydrometallurgical process involving the following steps: pretreatment, leaching, ion exchange, and two-step solvent extraction (I) and (II) using ionic liquids (ILs). First, an AlCrN film coating was completely removed from a WC-Co hard metal sample by leaching in a H2SO4–H3PO4 mixed acid medium at 423 K for 120 h. Then, the sample was oxidized at 1173 K for 10 h and XRD analysis showed that WO3 and CoWO4 were generated during this oxidization. After the oxidization, the leaching reaction WO3 + 2LiOH → WO42− + 2Li+ + H2O smoothly proceeded in leaching solution of 0.1 mol/L LiOH at 343 K for 19 h and the stoichiometry of WO3:LiOH was 1:2, which was consistent with that of the leaching reaction. Further, after the leaching step was completed, it was beneficial to exchange H+ and Li+ in the leaching solution using a cation exchange resin.Solvent extraction was performed using triethyl-n-pentyl phosphonium bis(trifluoromethylsulfonyl)amide as the IL, and tri-n-octylamine was employed as the extractant for the selective separation of W(VI) for solvent extraction (I). The extraction percentages (E) of W(VI) and Co(II) were >95% and <2.5% at pH = 1.0, respectively, and the selective extraction of W(VI) was confirmed in this study. The extraction mechanism of W(VI) was based on the ion association reaction n[R3N]org + [HxWyOzn−]aq + n[H+]aq ⇔ [(R3NH)nHxWyOz]org. In solvent extraction (II), a PC-88A/[P2225][NTf2] system was used for the effective extraction of Co(II) at pH > 4.3. The slope analysis results showed that the extraction mechanism was governed by the cation exchange reaction [Co2+]aq + 2[(HL)2]org ⇔ [CoL2·2HL]org + 2[H+]aq. A series of novel hydrometallurgical process using IL enabled us to demonstrate that W(VI) and Co(II) were efficiently recovered from WC-Co hard metal wastes.

Thermal stability and mechanical properties of HVOF/PVD duplex ceramic coatings produced by HVOF and cathodic vacuum arc

Duplex ceramic coatings, consisting of an inner NiCr-Cr3C2-based coating and an outmost AlCrN film, were produced on the steel substrate in succession by velocity oxygen-fuel spraying (HVOF) and cathodic vacuum arc methods, and then isochronally annealed at annealing temperatures below 900°C for 2h. The thermal stability and mechanical properties of the annealed samples were systematically studied by means of X-ray diffraction, Optical microscope and transmission electron microscope, in association with mechanical property measurements. The results show that the microstructure, phase evolution and mechanical properties of duplex ceramic coatings are significantly dependent on the annealing temperature. Metastable fcc-AlCrN solid solution in AlCrN film first decomposes to rich-Al and rich-Cr domains by spinodal decomposition at 700°C, leading to a notable increase in hardness due to its smaller grain size and high elastic strain field, and then to equiaxed hcp-AlN and Cr2N by the nucleation and growth at 900°C, leading to a notable decrease in hardness due to the recrystallization and the formation of hcp-AlN. Meanwhile, the both decarburization of Cr3C2 to Cr7C3 occurs at 800°C, but becomes more intensive at 900°C, leading to a notable loss in hardness. In addition, the dissolution of Cr3C2 produces high density of porosity, which also reduces the hardness. The hardness tests show the following ordering of load-bearing capacity for the duplex ceramic coatings: 700°C>As-deposited >800°C>900°C. Tribological property measurements demonstrate that the wear resistance of the tested duplex ceramic coatings obeys the following ordering: 700°C>As-deposited >800°C>900°C. The improved wear resistance is due to high surface hardness, load-bearing capacity and thermal stability. In addition, the wear mechanisms are shown.

Electronic structure of AlCrN films investigated using various photoelectron spectroscopies and ab initio calculations

The valence band (VB) structures of wurtzite AlCrN (Cr concentration: 0–17.1%), which show optical absorption in the ultraviolet-visible-infrared light region, were investigated via photoelectron yield spectroscopy (PYS), x-ray/ultraviolet photoelectron spectroscopy (XPS/UPS), and ab initio density of states (DOS) calculations. An obvious photoelectron emission threshold was observed ~5.3 eV from the vacuum level for AlCrN, whereas no emission was observed for AlN in the PYS spectra. Comparisons of XPS and UPS VB spectra and the calculated DOS imply that Cr 3d states are formed both at the top of the VB and in the AlN gap. These data suggest that Cr doping could be a viable option to produce new materials with relevant energy band structures for solar photoelectric conversion.

Structure and tribological properties of MoS2low friction thin films

The main aim of the studies was the deposition of the AlCrN film, covered by molybdenum disulphide (MoS2) – based lubricant, on the austenitic steel substrate. The AlCrN and MoS2 layers were deposited by PVD lateral rotating ARC-cathodes (LARC) and magnetron sputtering technology on the X6CrNiMoTi17-12-2 respectively. Structural characterizations of the MoS2 thin films have been carried out using SEM (scanning electron microscopy) and AFM (atomic force microscopy) to determine the surface topography as well as HRTEM (high-resolution transmission electron microscopy) and Raman spectroscopy for structural investigations. The tribological wear relationships using ball-on-disc test were specified for surface layers, determining the friction co-efficient and mass loss of the investigated surfaces. Tests of the coatings’ adhesion to the substrate material were made using the scratch test. HRTEM investigation shows an amorphous character of the MoS2 layer. In sliding dry friction conditions, the friction co-efficient for the investigated elements is set in the range between 0.4-0.5. The investigated coating reveals high wear resistance. The coating demonstrated a dense cross-sectional morphology as well as good adhesion to the substrate. The good properties of the PVD AlCrN+MoS2 coatings make them suitable in various engineering and industrial applications.

Mechanical response under contact loads of AlCrN-coated tool materials

The mechanical behavior under contact loading of systems consisting of PVD AlCrN film deposited onto two distinct hard substrates - cemented carbides and tool steel is studied by means of indentation testing techniques, under monotonic and cyclic condition. Experimental work includes assessment of critical applied loads for emergence of circular cracks at the coating surface, as well as evaluation of both surface and subsurface damage evolution. Results indicate that both coated systems are susceptible to mechanical degradation associated with repetitive contact load. Furthermore, significant differences on contact fatigue behavior between the two studied coated systems are evidenced under consideration of cracking evolution at top surface and penetration towards the substrate. In this regard, the intrinsic mechanical properties of the substrate are pointed out as key feature for rationalizing the experimental findings.