ICMCTF2017 Session BP: Symposium B Poster Session

The relationship between the nanostructure and nanoscale deformation behavior of nanocomposite coatings is of importance to their mechanical performance and thus of interest for investigation. In this study, multi-component face-centered cubic (fcc) (AlCrTaTiZr)N_x, (AlCrTaTiZr)NC_y and (AlCrTaTiZr)NSi_z coatings were prepared by sputtering, and their nanostructures and nanoscale plastic deformation behavior were characterized using nanoindentation and transmission electron microscopy. The multi-component (AlCrTaTiZr)N_x coating had a simple fcc solid-solution structure and exhibited a typical full dislocation-mediated plastic deformation. With the addition of C or Si (the incorporation of covalent –C or –Si bonds), an fcc nanocomposite structure (with small-angle domain boundaries) formed in the (AlCrTaTiZr)NC_y and (AlCrTaTiZr)NSi_z coatings. Large lattice strains (severe lattice distortions) in the multi-component nanocomposite coatings caused the change of plastic deformation behavior. Under a large indentation stress, low-energy small-angle dislocation structures (with extended partial dislocations or stacking faults) were formed at the small-angle domain boundaries. When the applied stress (the stored high strain energy) was released, many of the stacking faults were removed, and a near-perfect ordered crystal structure was observed. The activities of stacking fault decahedra consisting of highly reversible 1/6 <112> and 1/9 <222> partial dislocations were expected to dominate the plastic deformation and recovery (W_e ~ 76%) of the multi-component (AlCrTaTiZr)NC_y and (AlCrTaTiZr)NSi_z nanocomposite coatings.

The physical vapor deposition (PVD) is a commonly applied technology for deposition of hard coating systems such as chromium (Cr)-based nitride coatings on tools and components in tribological applications. In such applications the tools and components are subjected to complex loads, which can lead to elastic-plastic deformation of coating/substrate compounds or crack formation. One approach to increase the life time of compounds under significant loadings is the deposition of nanostructured coatings such as CrN/AlN-nanolaminates with promising hardness and crack resistance. The understanding of the deformation behavior of such multilayers is, however, a key factor for further coating developments. Implementation of nanoscratch analyses in conjunction with high resolution microscopy techniques is an approach to study the tribological behavior of nanostructured coatings and gain information about their plastic deformation under normal and lateral loads. Nanoscratch analyses on the coating system CrN/AlN-nanolaminate deposited on quenched and tempered AISI 420 steel substrate and investigations on the resulted plastic deformation are the subjects of current research. In the present work, a hybrid technology, consisting of direct current and high power pulse magnetron sputtering dcMS/HPPMS, was used for deposition of the coating. The CrN/AlN-nanolaminate was deposited with a bilayer period (thickness CrN + AlN) of Ʌ = 10 nm. In order to study the plastic deformation of the coating, nanoscratch analyses were performed applying a Berkovich tip. The deformation of coating system under nanoscratch loads was quantitatively analyzed by means of depth profiling using confocal laser scanning microscopy (CLSM). A comprehensive study of the plastic deformation and crack resistance was furthermore performed using scanning electron microscopy (SEM). The SEM analyses were carried out on surface and cross section fractures of the nanoscratch tracks. Scanning transmission electron microscopy (STEM) was applied to explore the micro-scale cracking underneath the nanoscratch tracks. High resolution transmission electron microscopy (HRTEM) was furthermore applied to explore the mechanism of plastic deformation of the investigated coatings. Based on the results, the CrN/AlN-nanolaminate exhibited a significant resistance against plastic deformation and crack formation. Furthermore, the plastic deformation of the investigated coating was explained by reorientation and sliding of grains imbedded in individual layers CrN and AlN.

CVD Alumina coating has been one of the most important components of coated cutting tools for many years. Recently, texture control in α-Al₂O₃ has attracted increasing attention due to the possibility to further improve the anisotropic properties such as thermal conductivity and mechanical properties. The influence of process parameters on textures is complex. In this study, we have investigated the influence of nucleation surface condition and catalyst (H₂S) on the texture in CVD α-Al₂O₃ coatings. The α-Al₂O₃ coatings were deposited by CVD in a hot wall vacuum deposition reactor on WC substrates, and were characterized by advanced analytical techniques including SEM, XRD and EBSD. It has been shown that without the addition of catalyst, the crystal orientation in the Al₂O₃ coatings is primarily dominated by the surface condition, while the effect of reactant composition on texture is minimal. On the other hand, in the presence of catalyst during growth, reactant composition also plays an important role in affecting the crystal orientation. This effect is likely due to the strong interaction between the surface the catalyst.

Nowadays the used materials or material combinations in all application fields (e.g. optical, avionic, fun sports or automotive industry) are getting more and more complex. These complex structures are needed in order to increase the performance and lifetime of the components. Such improvements of each part of your complex device, tool or structural element are necessary to reach the performance goals demanded by the desired application. This increased complexity demands extended analyzis and optimization methods. Engineering knowledge and rules of thumb aren't enough anymore.

Proper characterization and optimization of such structures requires invertible mathematical tools of sufficient holistic character. Unfortunately, as such tools are still not available one often finds trial and error or half empirical sensitivity analysis methods in combination with FEM or BEM. Faster tools could help here a lot to save development time and costs [1].

All models (FEM or analytical based) will need exact and generic material parameters for each part of our material system.

A few years ago, SIO developed a model and a dedicated software package called Oliver & Pharr for Coatings (OPfC® [2]) which allows the determination of true generic material parameters (like Young’s modulus and Yield strength) for a coating by knowing the parameters of the substrate and all underlying layers.

The software package FilmDoctor® [3] contains analytical models which dramatically speed up the simulation of complex contact situations compared to FEM systems.

The poster will focus on the results of a joint project with Naish international [5] about standup paddling boards and paddles. It will present how the models and software packages are used to improve the performance in critical application conditions dramatically.

References:

[1] N. SCHWARZER, Scale Invariant Mechanical Surface Optimization - Applying Analytical Time Dependent Contact Mechanics for Layered Structures, Proceedings of the 28th International Conference on Surface Modification Technologies, 287-327, SMT 28, June 16th – 18th, 2014, Tampere University of Technology, Tampere, Finland, Publisher: Valardocs, ISBN Number:978-81-926196-1-3

[2] www. [http://siomec.de/OPfC]

[3] www [http://siomec.de/FilmDoctor]

[4] www.naish.com

It will be presented how amorphous carbon coatings can be deposited at low temperatures with mechanical characteristics varying in a wide range depending on deposition parameters and that these properties such as hardness and elasticity can easily be assessed by Raman spectroscopy. For this the indentation hardness and indentation modulus of carbon films deposited at various laser pulse fluences were determined by means of nano indentation and brought into correlation with the peak ratio of the disordered (D-) and graphite (G-) peaks. This offers a fast and simple method to assess H_IT and E_IT for carbon single layers, for the presented coatings in the range of roughly 20 GPa to 60 GPa and 290 GPa to 620 GPa, respectively.

It will also be shown that the architecture of films designed as multilayered stacks of such different carbon compounds strongly affects the toughness of protective coatings when exposed to high mechanical stresses induced in scratch test or indentation at high loads. Nano indentation measurements showed that this multilayered design does not result in a loss in hardness and elasticity if suitable layer structures are built up. The preliminary computation of stress evolution in the film-substrate system and the actual layer behavior for several layer stack designs will be part of the presentation as well. These coating systems combine a very good adhesion on several metal and hard metal substrates, very high hardness and low abrasive wear, very high elasticity up to 80 % elastic recovery in nano indentation and high crack resistivity in scratch tests and indentation experiments. These superior properties indicate the high potential of laser deposited carbon multilayer as wear protective coatings for cutting tools, bearings and engine components to name but a few.

Information is still scarce concerning the properties of single-crystal cubic metastable TaN thin films. This work aims at providing some new insights on the elastic and structural properties of TaN epitaxial nitride thin films, especially regarding the influence of defects and nitrogen stoichiometry. 150 nm-thick TaN films were deposited by magnetron sputtering under reactive Ar+N₂ plasma discharges on MgO(001), (110) and (111)- oriented substrates, at a temperature of 650°C. In parallel, ab initio calculations were performed in the framework of the density functional theory (DFT) using the VASP software. It has been evaluated how vacancies influence the lattice parameter, the mass density and elastic constants of c-TaN.

The thickness and mass density were determined by x-ray reflectivity measurements, while x-ray diffraction pole figure and reciprocal space maps were employed to study epitaxial orientation and determine the lattice parameters. Elastic constants of thin films can be accurately studied by photoacoustic measurements. The Brillouin light scattering (BLS) technique allows measuring sound velocity of a few kinds of surface acoustic waves (V_SAW) in thin films and thus estimating single-crystal elastic constants (ρV²), in the case of epitaxial films, if the mass density ρ of the film is known. The Rayleigh surface wave is much more dependent on the shear elastic constant C₄₄, thus BLS can provide at least this constant. It is well adapted for thin films and can be conveniently combined with the picosecond ultrasonics technique that measures the sound velocity of longitudinal waves (V_L) that are travelling forth and back within the film along the direction perpendicular to the film plane, i.e. [001], [110] and [111] crystallographic directions.

Density Functional Theory is a well established tool for predicting structural and mechanical properties of bulk materials. Recent progress facilitated by modern efficient codes and increased computational power has opened doors to studying also extended systems. Examples of such are superlattices, an important design approach of materials with controlled architecture.

In this contribution, we will report on first principles calculations of structural and mechanical properties of CrN/AlN superlattices. The ab initio predicted oscillating interplanar distances are corroborated by high-resolution transmission electron microscopy analysis. Further on, we will present fully quantum mechanical calculations of directionally-resolved Young's modulus [1]. We will demonstrate that these yield comparable results with a simple continuum model of Grimsditch and Nizzoli [2]. Also these predictions are in excellent agreement with experimental measurements [1]. Finally, we will discuss the ideal tensile strength of these superlattices.

References:

[1] M. Friak, D. Tytko, D. Holec, P.-P. Choi, P. Eisenlohr, D. Raabe, and J. Neugebauer, New J. Phys. 17, 093004 (2015).

[2] M. Grimsditch and F. Nizzoli, Phys. Rev. B Condens. Matter 33, 5891 (1986).

This work enhance the mechanical properties on pearlitic gray cats iron with hard coating under hydrogen charging. The formation of hard coating was carry out by boron paste dehydrated at temperature of 1173 and 1193 K, with 8 hour exposure time. The characterization of hard coating were using: optical microscopy (OM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and the mechanical properties: elastic modulus and hardness were obtained nanoindentation and the adhesion by Rockwell C indentation test. All sample boride were subjected to hydrogen charging and evaluate the behavior of hydrogen on gray cast iron with FeB/Fe₂Bcoating using three point bending results. The mechanical properties enhance the surface on gray cast iron due to hard coatings and increase the bending stress value.

B-doped diamond was synthesized on single crystalline diamond substrates using mode conversion type microwave plasma CVD apparatus. HPHT diamond substrates were synthesized using high pressure high temperature method and their (1 0 0) facets were crystal orientation. Reaction gases were used CH₄ (15 SCCM) and H₂ (100 SCCM). Trimethyl-borate was used as a boron source. Vapor of trimethyl-borate was carried by H₂ carrier gas into the vacuum chamber with its flow rate of 3 SCCM. Pressure was 20.0 kPa and microwave power was 1.0 kW, respectively. The surface and cross sectional morphologies of deposits were observed by SEM. Qualities of the deposits were estimated by Raman spectroscopy and Laue pattern. Electrical resistivities were measured by the four-point probe method.

Diamond has excellent physical and chemical properties such as high hardness, high thermal conductivity, optical transmission from UV to IR and chemical inertness. In addition, diamond is well known an electrical insulator with a resistivity order of 10¹⁶ Ω･cm. However it was changed to the semiconductor by inclusion of dopants such as boron or phosphorus. However, the liquid B source in the bubbling tank was evaporated at room temperature, it is difficult to control flow rates because it is introduced using H₂ carrier gas, and control range is so narrow. Towards further industrial applications, it is desirable to extend electrical resistivities range by using a relatively less toxic liquid B source. Application to a variety of electronic components to be able to safely control the volume resistivities of the B-doped diamond can be expected to spread.

The investigation was carried on the effects of the reaction gas flow rates on the plasma state during boron-doped diamond synthesis.

Boron-doped diamond films were synthesized using mode-conversion type microwave plasma CVD apparatus. Si substrate was scratched by diamond powder and then cleaned ultrasonically in acetone solution. Reaction gases were used CH₄ and H₂. Vapor of B(OCH₃)₃, the boron source, was introduced by H₂ carrier gas into the vacuum chamber. Their flow rate was H₂/CH₄/H₂ carrier=100/15/3, 200/30/6, 300/45/9 sccm , respectively pressure was 20.0 kPa and microwave power was 1.0 kW. Reaction time was fixed to 3h. During synthesis, plasma states were estimated using optical emission spectroscopy (OES) . The surface was observed by SEM. Qualities of the deposits were estimated by Raman spectroscopy. Volume resistivities were measured by the four-point probe method.

As a result of OES, the peaks of B(249nm), BH(433nm), BO(436nm), CH(387nm,431nm), H_α(656nm), H_β(486nm) and C₂(404nm, 406nm, 473nm, 516nm, 563nm, 619nm) were observed for each conditions. In the SEM observation, the grain sizes of deposits were 1 to 3 mm. In the Raman spectra of the deposits, the broad peak at about 500, 1230 cm^-1 and the weak peak at 1333 cm^-1 were obtained for each samples . These peaks due to inclusion of high concentration boron in the films. As a result of the electrical resistivity measurements by the four-point probe method, the minimum Volume resistivities of 0.2Ω・cm was obtained. With the reducing of B/Hα, BH/Hα and BO/Hα emission intensity ratio in emission spect ra, volume resistivity is reduced.

As a conclusion, relationship between volume resistivit ies of boron doped diamond and intensity ratio of B-system emissions in OES spectra was suggested.

Carbon nitride has fascinated properties such as high hardness and high current density of field emission. In addition, if a β-C₃N₄ or c-C₃N₄ structure can be synthesized, it is possible to obtain a hardness higher than that of diamond. Our laboratory had investigated to obtain crystalline carbon nitride, and α-C₃N₄ was obtained from a CH₄ – N₂ reaction gas system by microwave plasma CVD. In addition, pulse plasma is possible to control the state of plasma such as electron temperature. Also, pulse microwave CVD is possible to vary particle size and density.

Investigation was carried out on the effects of pulse frequency and duty cycle on synthesis of carbon nitride using pulse microwave plasma CVD。

Carbon nitride was synthesized using an improved microwave plasma CVD apparatus equipped with a water cooled substrate holder and can be selected microwave radiation mode cw or pulse. Si was used as the substrate. A mixture of CH₄ and N₂ was used as a reaction gas system. CH₄ and N₂ flow rates were 2 and 200 SCCM, pressure was 4.0 kPa. The reaction time was 5h. The reaction time was at 5h and the peak microwave power was 1000W. Pulse frequency was varied from 30, 300 and 3000Hz, duty cycle was varied 30, 50 and 70%. The deposits were estimated by Scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS). The plasma state was estimated by Optical emission spectroscopy (OES).

As a result of SEM observation, crystalline particles were obtained at pulse frequency of 30Hz, duty cycle of 50 and 70%, at frequency of 300 and 3000Hz, duty cycle of 30, 50 and 70%. However, Ball-like particles were obtained at pulse frequency of 30Hz and duty cycle of 30%. Particle densities were from 6.2×10⁷ to 2.3×10⁸ numbers/cm². Particle density was lowered with decreasing of duty cycle. As a result of Raman spectroscopy, the peak corresponding to Si was observed at pulse frequency of 30 to 3000Hz and duty cycle of 30 to 70%. On the other hand, the peak corresponding to amorphous carbon was observed at pulse frequency of 30Hz and duty cycle of 30%. As a result of XPS, the Si₃N₄ and C-N bond peaks were observed in at all sample. In OES spectra, the peak of CN radical emission was observed for all condition.

Examination result of effect of pulse frequency and duty cycle of microwave plasma on carbon nitride synthesis, crystalline carbon nitride was obtained proper synthesis condition. Also, Particle densities were about 6.2×10⁷ to 2.3×10⁸ numbers/cm². Particle density was lowered with decreasing of duty cycle.

Diamond-like carbon (DLC) is applied to a wide variety of fields in the industry because of its tribological properties and hardness. However, one of the major issues is the adhesion strength between DLC films and the metal substrate. Many efforts have been made to obtain a higher adhesion strength, such as the formation of an interlayer and the modification of the surface layer. In contrast, radical nitriding is one of the most suitable methods for the pretreatment of duplex coatings, because it possible to increase the surface hardness while maintaining the roughness of the original surface. According to this process, a diffusion layer is formed in the surface region using plasma state control.

High-speed tool steel was used as the substrate. A radical nitridation apparatus was used for the radical nitriding and PNC processes. The conditions for the radical nitriding process were a pressure of 133 Pa, an applied voltage of −380 V, an H₂ flow rate of 50 SCCM, an NH₃ flow rate of 50 SCCM, an external heater temperature of 843 K, and a processing of 60 min. The conditions for the PNC process after radical nitriding were a pressure of 532 Pa, an applied voltage of −380 V, an H₂ flow rate of 50 SCCM, an NH₃ flow rate of 50 SCCM, a CH₄ flow rate of 50 SCCM, an N₂ flow rate of 1 SCCM, an external heater temperature of 843 K, and processing times that were varied from 5 to 10 to 15 min.

After the plasma treatment process, the DLC film was coated onto the substrate using RF magnetron sputtering equipment. The target was graphite, the sputtering gas was Ar, the RF power was 50 W, the pressure was 0.4 Pa, and the processing time was 60 min, respectively. The DLC films were prepared after pre-sputtering under the same conditions for 10 min. The DLC film thickness was 300 nm.

DLC coated on an untreated substrate exhibited extensive delamination and micro-cracks that extended from the vicinity of the crater. High adhesion strength of DLC coatings on high-speed tool steel was accomplished via PNC treatments. In particular, PNC showed the best adhesion strength in this study at 5 min after radical nitriding.

Radical nitriding formed a nitrogen-diffusion layer, followed by the formation of a carbon layer by nitrocarburizing without the formation of a brittle compound layer. It maintained surface roughness compared with the untreated substrate. The resulting DLC films exhibited better adhesion to the treated-steel substrates than to the untreated ones.

Diamond-like carbon (DLC) is an attractive carbon-based coating material for many applications due to their unique combination of low-friction, self-lubrication and high wear resistance in conjunction with good biocompatibility. However, the metastable nature of the amorphous structure restricts the wide application of DLC coatings under harsh conditions. Although there have been many reports on the thermal stability of DLC, limited or no work has been conducted to investigate the stability of DLC coatings under both thermal and pressure conditions.

This work presents a study on the stability of DLC coatings: a-C, a-C:H, a-C:Si and a-C:H:Si thermo-mechanical conditions using a hot isostatic pressure (HIP) furnace to apply both high-temperature and high-pressure. In order to investigate the influence of the applied pressure, thermal stability was also conducted by heating the DLC samples up to 600ºC in air and in argon without pressure. The microstructure of the as-deposited, heat treated and HIPped DLC samples were fully studied using XRD, Raman, FIB/SEM and XTEM; the change of their mechanical and tribological properties were investigated using nano-indentation and tribo-meters.

The experimental results reveal that the high isostatic pressure introduced during HIPping accelerated the graphitization process and hence reduced the stability of these DLC coatings at elevated temperature; the introduced isostatic pressure also reduced the adhesion between the top DLC coatings and the substrates. The mechanisms involved are discussed based on XTEM, XPS and Raman analysis.

DLC is a metastable form of amorphous carbon that has excellent properties such as high hardness, high elastic modulus, chemical inertness, high wear resistance, and low friction coefficient. DLC has been studied as a promising solid lubricant since liquid lubricants are ineffective and undesirable for many space applications. Solid lubricants require performing properly under space environment conditions, such as high vacuum. This paper reports the structure, morphology, adhesion, and high-vacuum tribologcal performance of DLC films with different hydrogen content. The films were deposited by pulsed DC PECVD technique with an additional cathode and using acetylene as a precursor gas. An amorphous silicon interlayer was deposited in order to guarantee the adhesion between coating and substrate. For the films characterization, Raman spectroscopy, Scanning Electron Microscopy (SEM), Rockwell C indentation test, and scratch test were performed. In addition, hydrogen content in the DLC films was determined by Elastic Recoil Detection Analysis (ERDA). Friction coefficient value and wear rate of DLC films in high vacuum conditions were obtained applying loads of 2N and 5N at different sliding speeds. Results showed that DLC films deposited by pulsed DC PECVD can act as a space solid lubricant due to its low friction coefficient value, high adhesion and keeping its structural quality in high vacuum environment.

The carbon-related materials have been attracting lots of attention for decades in flat panel display, optoelectronic devices, etc. due to their unique chemical, electronical, mechanical, and thermal properties. In this study, amorphous nitrogenated carbon (a-C:N) films have been prepared on silicon wafer at 800°C with varying substrate bias upto -650V in a 90^o-bend filtered cathodic arc plasma (FCAP) system. The magnetic coil removes neutral carbon atoms and macroparticles from the plasma stream and in this case only the carbon arc discharge is available to form nitrogen ions. XRD showed the peak of (111) plane actually from the nanodiamond nucleated in the a-C:N films and agreed well with the result of HRTEM of d-spacing of 1.76 Å. The hardness of the resulting film was found to be 12.2GPa under an optimal bias of -350V.

The ratio of I_D/I_G of the Raman analysis increased to ~3.5 under the bias of -350V, indicating enriched sp³-bonded carbon of the graphite domain. The FTIR spectra showed that the higher intensity at 1330cm^-1 of D-band and 709 cm^-1 of plane bending mode resulting from the graphite-like domains with N ions incorporated; more sp³ bonds facilitated the completion of the nanodiamond structure. Binding energies of C1s, e.g., 287.6 (sp³), 285.5 (sp²), and 284.6 eV (free carbon), and N1s, e.g., 402.0 (N-O), 400.0 (sp²), and 399.0 (sp³) eV, have been resolved in the XPS spectra. The ratios of N/C were able to reach as high as 50% at -350V, indicating that higher substrate temperatures together with higher contents of nitrogen promotes the sp³ clusters in the a-C:N films. These properties and the structure of the a-C:N film are sensitive to the energy of depositing C⁺ and strongly dependent on the substrate bias.

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In 2015 the automobile production and therefore also the transmission production exceeds the 90 million. Containing of several gears the manufacturing is of major importance. As the dominating green manufacturing process gear hobbing is applied the most. Here cutting conditions regarding chip thickness and cutting length change continuously within every generating position. Hence, the load at the cutting edge varies critically too and affects abrasive and crater wear on the tool. Nowadays gear hobbing is performed more and more without coolant which intensifies the thermal load and thus the wear phenomena.

To examine the performance of different coatings, cutting trials were carried out using the well-established fly-cutter analogy test. Subsequently the worn out single hob teeth are examined by REM and fringe projection to evaluate the wear phenomena.

To reduce crater wear and to extend the lifetime of gear cutting tools a range of AlCrN-based coatings was deposited in an industrial π411 rotating arc cathodes PVD unit. Significant performance differences between the chemically and structurally modified coatings were found. In this contribution the authors are focusing on the influence of the internal stress of AlCrN-based Hard Nitride Coatings on the wear behavior and tool life for both, high speed steel and solid carbide fly-cutters.

Hard coatings have been widely employed in tools, dies and wear-resistant parts. Most commercial coatings are limit in a few microns due to the adhesion problem induced by the stress developed at the film/substrate interface during film deposition and subsequent cooling processes. The residual stress state is considered to be key factor governing the adhesion of thick hard coatings. It is significant to understand the relationship between the residual stress and the bonding strength of hard coatings.

In this work, one group of TiN coatings was prepared by multi-arc ion plating (MAIP). In order to investigate the influence of the residual stress on coating’s adhesion, all coatings were synthesized with the same pretreatment and interlayer to obtain an identical interfacial state. During the coating deposition, the working pressure and bias voltage were varied respectively to obtain different residual stress. The average residual stress of the coatings was calculated from the bending deformation of the sliced steel substrate. The bias voltage is shown to have a strong impact on the residual stress of coatings. As the bias voltage increases from -10 V to -200 V, the residual stress increases from -1.8GPa to -3.2 GPa for the coatings with thickness of 10 μm, and the corresponding critical load by scratch test decreases from 60N to 40N. The working pressure is another important parameter that affects the residual stress. The stress level of the coating deposited under 6 Pa is -1.8 GPa in comparison to -2.2 GPa which deposited under 1 Pa, and the critical load by scratch is higher. Higher bias or lower working pressure may cause higher ion energy transferred to deposition ions, and produce fine grain structure.

Diamond-like carbon (DLC) coatings exhibit excellent mechanical, electrical and optical properties such as high hardness, low friction coefficient, high refractive index which make them attractive for a wide range of applications from cutting tools to engine components. The main limitations of existing DLC solutions stem from its high internal stresses and limited thermal stability. High internal stresses in excess of ~10 GPa limit the maximum achievable thickness due to poor adhesion and limited thermal stability makes DLCs unsuitable for high temperature applications. In order to address these issues, strategies for developing a new generation of DLC coatings exhibiting low-stresses, high hardness, good adhesion and good thermal stability are desired.

This work deals with the development of a deposition process for DLC coatings based on High Power Impulse Magnetron Sputtering (HiPIMS). We synthesize DLC coatings using Ne-based HiPIMS process to enhance the ionization of C. For comparison, plasma and film properties using standard Ar-HiPIMS process are also studied.

Acknowledgement: The work has been carried out in frame of M-Era.Net project TANDEM supported by VINNOVA.

Corrosion of metal is costly material science problems which originate from the day of metal discovery. Corrosion inhibitor usage is an effective way of addressing metallic corrosion in aggressive environments but continued usage of synthetic chemicals for inhibiting corrosion is indefensible as a result of toxicity of the chemicals to the environmental ecosystem. Eco-friendly corrosion inhibiting alternatives, including plant-extract usage, are therefore needed. Characterization of this nanoparticles material will be studied using. Ultra violet analysis, morphology by SEM-EDS and TEM analyses, phase composition by XRD analyses, inorganic element constitute analyses by RAMAN spectroscopy and organic element constituents’ analyses by FTIR spectroscopy. Effect of the nanoparticles on metallic samples in different aggressive environment will be studied in the laboratory using weight loss method. The samples exposed to the inhibitors showed a lower corrosion rate values and excellent polarization resistance as compared with the corrosion rate samples without inhibitor. Grey relational used in this research correspond with the experimental results.

Reactive radio-frequency magnetron sputtering technique was employed to study the deposition conditions for crystalline chromium oxide films with Cr₂O₃ stoichiometry. Chromium oxide coatings with a thickness of 1-2 micrometers were deposited on Silicon wafers under various oxygen partial pressures and substrate temperatures. The effect of deposition parameters on the chemical composition, crystal structure, microstructure, phase composition, and hardness of coatings were investigated by electron dispersive spectroscopy, X-ray diffraction (XRD), scanning electron microscope, Raman spectroscopy, and nanoindentation, respectively. Crystalline coatings obtained by increasing the oxygen flow rate or the substrate temperature, however vitrification of coatings was triggered again by flowing more oxygen. No coatings could be deposited at temperatures higher than 300 ^o C due to volatilization behavior of chromium oxides at high temperatures. The results illustrated that pure crystalline Cr₂O₃ coatings with highest hardness could be obtained at a substrate temperature of 300 ^o C and an oxygen content of 6 vol. %.

Ti–Al–N thin films are well established due to their outstanding thermo-mechanical properties. Nevertheless, this system is still a subject of many research activities to further enhance their oxidation resistance and thermal stability. The addition of reactive elements, such as Cerium, can significantly improve especially the oxidation resistance of various materials. Therefore, we study in detail the impact of Ce (2 at% alloyed to powder metallurgically prepared Ti_0.50Al_0.50 targets) on growth processes, structure, mechanical properties, thermal stability, and oxidation resistance of magnetron sputtered Ti_1-x-yAl_xCe_yN coatings prepared with DC bias potentials of U_bias = -25, -50, -75, and -100 V. The deposition rate is significantly increased by a factor of ~1.75 (U_bias = -25 V) to 1.45 (U_bias = -100 V) when using Ti_0.49Al_0.49Ce_0.02 instead of Ti_0.50Al_0.50 targets. Furthermore, also the hardness of the resulting single phase face centered cubic Ti_0.43Al_0.55Ce_0.02N is with ~35.2 GPa above that of Ti_0.42Al_0.58N with ~33.7 GPa, for coatings on polycrystalline Al₂O₃ and U_bias = -50 V. Coatings on steel substrates typically show ~5 GPa higher values.

All temperature dependent characteristics of Ti_0.42Al_0.58N are improved significantly by the addition of Cerium. Wurtzite-structured AlN formation within Ti_0.43Al_0.55Ce_0.02N can only be detected at T_a = 1100 °C, about 200 °C higher as for Ti_0.42Al_0.58N. Their peak-hardness, due to spinodal decomposition of the supersaturated cubic phase is ~37.0 GPa with T_a = 900 °C, as compared to 34.6 GPa with T_a =800 °C for Ti_0.42Al_0.58N. Additionally, even after exposure to ambient air at 950 °C for 3 h, still > 50 % of the Ti_0.43Al_0.55Ce_0.02N coating is intact (below the ~1.2 µm thin oxide scale), whereas Ti_0.42Al_0.58N is already fully oxidized.

Based on our results we can conclude, that Ce-doping improves the deposition characteristics and mechanical properties as well as thermal stabilities (incl. oxidation resistance) of Ti–Al–N, to be used as protective coatings for a wide range of high-demanding applications.

The protection of various tools and components through wear resistant coatings is imperative in highly efficient and precise industrial manufacturing processes. Especially, physical vapour deposited Ti_1-xAl_xN and Cr_1-xAl_xN coatings have been commonly used as hard protective coatings due to their outstanding thermal stability and mechanical strength. However, to increase the applicable working temperatures by simultaneously enhancing the wear performance (e.g., to allow for higher cutting speeds) further improvements are required.

Therefore, we studied in detail the impact of tungsten (W)—in combination with the substrate bias potential (U_bias)—on the thermo-mechanical properties and wear performance of arc evaporated

Ti_1-x-yAl_xW_yN thin films. With increasing W content the quality of our coatings significantly increases due to pronounced reduction of growth defects (quantity of macro particles). All coatings studied crystallise in a supersaturated, single-phased face-centred cubic Ti_1-x-yAl_xW_yN structure and their hardness (H) increases whereas the indentation modulus (E) decreases with increasing W content. This results in increased H³/E² values, with a maximum of 0.19 GPa for Ti_0.50Al_0.41W_0.09N prepared with U_bias = -120 V (H ≈ 35 GPa, E ≈ 483 GPa). All W-alloyed coatings exhibit wear rates below 2∙10^-5 mm³/Nm during our dry sliding pin-on-disk tests against alumina balls at room temperature, with a tendency for reduced values if more droplets are present. The highest thermal stability, with respect to the decomposition of the supersaturated Ti_1-x-yAl_xW_yN phase towards the stable constituents (at high temperature) TiN, AlN, and W, is obtained for Ti_0.53Al_0.42W_0.05N prepared with U_bias = -80 V. Here, the formation of the wurtzite-structured AlN can be delayed to 1000 °C after 60 min lasting isothermal annealings in vacuum.