To protect forming tools and components from abrasion, adhesion and corrosion, the application of thin hard coatings by physical vapor deposition is state-of-the-art. The use of a hybrid coating technology, consisting of high power pulse magnetron sputtering (HPPMS) and direct current Magnetron Sputtering (dcMS), allows a combination of the advantageous properties of both. HPPMS coatings for examples show a dense morphology, high hardness and smooth surface. Using dcMS, higher deposition rates can be achieved, resulting in a higher economic efficiently. Within the scope of this work, a novel multilayer coating concept of the material system Ti–Al–O–N was developed. The coatings were deposited using an industrial coating unit. Cold work steel X42Cr13 was used as substrate material. The coatings consist of a metallic titanium bond coat and a nitride TiN/AlN nanolayer as an interlayer. The nanolayer coating architecture leads to a dense, compact and fine crystalline morphology with smooth surfaces. Finally, an oxynitride toplayer with two different oxygen contents was applied. In order to investigate the coating durability relevant for polycarbonate melt processing, electrochemical impedance spectroscopy and linear sweep voltammetry were carried out in borate buffer, NaClO4 and benzoic acid electrolyte. An increased oxygen content in the oxynitride toplayer led to a decreased interfacial current density.

Hard coatings deposited by physical vapor deposition are state of the art for wear and corrosion protection of manufacturing tools. Nanolaminate coatings such as CrN/AlN consist of hundreds of CrN and AlN alternating layers and stand out among nitride hard coatings by their mechanical properties, i.e., high hardness combined with high toughness. Until now, the characteristics of CrN/AlN nanolaminates deposited in large scale industrial coating units using simultaneous direct current magnetron sputtering (dcMS) and high power pulsed magnetron sputtering (HPPMS) power supplies in hybrid dcMS/HPPMS processes have hardly been investigated. In this paper, two CrN/AlN nanolaminates are compared, which were deposited on tool steel X42Cr13 in a hybrid process using an industrial coating unit with six cathodes. Analyses of the mechanical properties were performed by nanoindentation in the low and high range load regimes as well as under very high quasistatic loads using the Rockwell penetration test. The residual stresses of the coatings were investigated using a dedicated ring-core milling method based on a focused ion beam. One of the two coatings was found to have a very high compound adhesion to the steel substrate rated with the best adhesion category HF1, despite residual compressive stresses of σ ≈ −5.4 GPa. This coating system also showed significantly higher hardness, compressive strength, and crack resistance compared with the other coating for which residual compressive stresses of only σ ≈ −0.9 GPa were measured. The relationship between the adjustable residual stresses in nanolaminate hard coatings and the strength requirements in the application can be used for the targeted design of coatings for manufacturing tools. The residual stresses and the influence of the rotation and bias voltage on those were analyzed for the first time for nanolaminates using the focus ion beam ring-core milling method.

Ternary hard coatings like TiAlN and CrAlN are used to improve the tool lifetime during cutting. The addition of silicon leads to a nanocomposite coating architecture with advantageous properties, like a higher oxidation stability and higher indentation hardness. The coating system TiAlCrSiON is a combination of TiAlN and CrAlN with added oxygen: This coating is not sufficiently studied yet. However, it has a great potential to improve the cutting performance and tool lifetime. In the current study, three different TiAlCrSiON nanolayer coatings were deposited by direct current magnetron sputtering/high power pulsed magnetron sputtering hybrid processes on an industrial coating unit using three different gas flow ratios of oxygen to nitrogen. Bases on these coatings the influence of the incorporation of oxygen into the TiAlCrSiON coatings on the coating process and properties as well as on the thermal and oxidation stability is studied. The morphology of the coatings was investigated by scanning electron microscopy and transmission electron microscopy. It becomes increasingly columnar, when oxygen is incorporated into the coating. The phase composition was examined by X-ray diffraction. The results indicate an incorporation of oxygen into the cubic crystal lattice. The coatings show a nanocomposite and a nanolayer coating architecture. The oxygen is distributed inhomogeneously over the coating thickness and homogeneously within the nanolayers. Moreover, the coatings were investigated by nanoindentation. When the oxygen content increases, the indentation hardness decreases from H-IT = (34 +/- 2) GPa for the nitride Ti21Al17Cr5Si3N54 coating to H-IT = (26 +/- 2) GPa for the oxynitride Ti23Al13Cr5Si3O21N35 coating with a high oxygen content. The coatings show a high phase stability even at T = 1200 degrees C. The oxidation stability of the oxynitride coating with a high oxygen content is decreased T = 900 degrees C compared to the nitride coating.

In conventional high power impulse magnetron sputtering processes (HPPMS) short pulses of a negative voltage are used to maintain the discharge. A new approach to accelerate ionized species towards the substrate position and subsequently improved coating properties is the use of a power supply, which generates a reverse positive pulse immediately after the negative pulse. In the present paper the influence of the frequency f and the pulse on time ton for a CrAlN process on the coating properties is investigated. All experiments were carried out on an industrial scale coating unit. In the present investigations coatings deposited by three different duty cycles are compared. For each duty cycle one coating was deposited using a conventional power supply and one coating using a power supply with a positive pulse. The positive pulse was clearly detected. It was found that the height of the positive pulse depends on the chosen pulse parameters. Furthermore, higher values of the peak power were found when using a power supply with a positive pulse, which should influence the ionization of the sputtered material. Regarding the chemical composition, a decreasing nitrogen content of the coatings was found when using a positive pulse. The investigations of the deposited coatings showed a denser morphology and increased values of the indentation hardness when using a power supply with a positive pulse compared to a conventional power supply. In addition to the higher indentation hardness, even the amount of plastic work showed increasing values for the power supply using a positive pulse compared to the conventional power supply. Furthermore, increased values of the roughness for coatings deposited on cemented carbide were found when using a positive pulse. The coatings deposited on cemented carbide showed a higher adhesion when using a positive pulse.

During the hard machining of powder metallurgical high-speed steel, finely dispersed carbides in the steel expose the tools to both thermal and mechanical load. This can influence the cutting performance and cause damage to the tools such as premature abrasive and adhesive wear. Thin hard coatings like TiAlN deposited by physical vapor deposition are widely used in order to improve the tool performance. High power pulsed magnetron sputtering (HPPMS) results in technical benefits, such as a more homogeneous coating thickness distribution on the tools compared to direct current magnetron sputtering (dcMS). The advantages of HPPMS can be combined with the high deposition rates of dcMS leading to a higher economic efficiency conducting a dcMS/HPPMS hybrid process. Adding silicon to the coating system TiAlCrN results in TiAlCrSiN leading to a nanocomposite coating architecture with improved mechanical properties. The influence of the residual stresses on the mechanical properties and on the roughing performance of nanocomposite coatings is of high interest and was therefore investigated in the present study. Four different TiAlCrSiN hybrid coatings deposited with four different substrate bias potentials were examined for this purpose. The residual stresses and the mechanical properties including the resistance against crack formation as well as the compound properties of the coatings on cemented carbide were investigated. Finally, the roughing performance of the coated cemented carbide tools were tested by milling the powder metallurgical high-speed steel HS6-5-3C. For the coatings investigated, it can be concluded that a compressive residual stress state of approx.-2 GPa < Sigma <-3 GPa leads to the highest resistance against crack formation, and thus to the best cutting performance.

Nanolaminate coatings consisting of hundreds of alternating CrN and AlN nanolayers can be used as protective coatings on various manufacturing technology tools. In this work, a coating is investigated, which is deposited using a hybrid direct current and high power pulse magnetron sputtering technology. The coating exhibits a nanolaminate architecture and its nanolayers consist of cubic CrAlN and AlCrN ternary solid solution phases. In order to study the thermal stability especially in the near-surface area of the coating, it is heat treated by using a continuous-wave laser at two different laser power densities. Laser induced heat-affected zone as well as punctual Al-rich precipitates, which are formed at the interface between the Al-rich AlCrN nanolayers and the column boundaries, are investigated using transmission electron microscopy. Moreover, it is demonstrated that the indentation hardness and indentation modulus of the coating are affected only to a small extent by the continuous-wave laser heat treatment.

In a high power pulsed magnetron sputtering (HPPMS) process a substrate bias is applied to affect the ions in the coating chamber and therefore the coating properties. For this reason the present experiments on an industrial scale coating unit are focusing on the identification of correlations between plasma and coating properties for a CrAlN process while using a pulsed substrate bias. The measurements regarding the plasma properties were carried out on the substrate side for a better understanding of the interaction of plasma and coating properties. These investigations should point out the significant potential of plasma diagnostics for measuring plasma properties to contribute to improved coating processes using pulsed substrate bias U-B,U-p. For this purpose a substrate bias synchronized to the HPPMS pulse is used since the pulsed bias can influence ions of a specific species. It was found that the even low values of a pulsed substrate bias lead to high values of the Debye sheath thickness and thus to a shielding of opposite surfaces. For complex shaped substrates like cemented carbide cutting inserts a better coatability for pulsed substrate bias up to U-B,U-p = -150 V was reached. Also increased values of the mean ion energy and the ion flux density were found compared to the use of a continuous substrate bias. Regarding the chemical composition a significant higher nitrogen content of the coatings was found when using a pulsed substrate bias compared to the use of a continuous substrate bias. Comparing the indentation hardness of a process using a pulsed substrate bias increased hardness values were found compared to the use of a continuous substrate bias. Generally, a significant change of both, plasma and coating properties was found when changing the mode of substrate bias.

In manufacturing technology, the performance of the tools have to conform to increasingly higher standards. Aditionally, recording process data during production is becoming more and more important in the Industrie 4.0. Thin hard tool coatings deposited by physical vapor deposition (PVD) and serving as protection from wear and corrosion are state of the art in manufacturing technology since decades. Integrating additional functions into the coatings will help extend the process limits faced by the load collective in manufacturing technology. One approach here is to exploit the electrical properties of thin coatings to design sensors for temperature measurement. The overall objective of this study is therefore the design PVD sensor coatings. These coatings should facilitate an online measurement of the surface temperature and offer a thermal resistance up to a few hundred degrees centigrade that allows their application in different technical applications. The hard coatings are selected for the two multilayer sensor coatings presented, because they are state of the art as wear protection for numerous manufacturing technology tools. Their temperature sensor function is based on the thermoelectric effect, expected because of the metallic bonding parts of the single coatings. Electrically insulated by Al2O3, the one material pair consists of CrN/AlN and TiAlN layers. The other material pair consists of a CrAlN and a TiAlN layer. Both sensor coatings show a dense and fine crystalline morphology as well as interlayer without cracks or damages in the SEM crosssection, even between the oxide insulation layer and the nitride sensor layers. Phase stability and oxidation resistance up to at least T <= 700 degrees C are demonstrated for all coating materials. For both sensor coatings, the ability to measure potential differences as a function of the applied temperature is demonstrated. The sensor coating, which in addition to TiAlN consists of a second sensor layer CrN/AlN with nanolaminate architecture, shows a better response behavior and a lower scattering of the measuring values.

In the current study, the three different HPPMS deposited wear protection coating systems CrAlN+Mo:S, CrAlON, and TiAlCrSiN were investigated. A special planing test setup enabeling the simultaneous measurement of the contact length between chip and rake face, the chip thickness and the coeffi-cient of friction during planing was used. Process forces and chip formation can be analysed on basis of high-speed recordings. The influence of the coating on the contact length, the chip thickness and the coefficient of friction during planing as well as the the influence of the cutting speed were investigated. The CrAlON coated tool showed a lower adhesion tendency against the steel workpiece compared to the CrAlN+Mo:S and TiAlCrSiN coated tools at all cutting speeds investigated. This prevented adhesive wear and reduced friction which decreased the chip thickness during planing. Moreover, the CrAlON coated tool showed a reduced contact length. A reduced friction and a reduced contact length are generally accompanied by decreased thermal tool load and therefore enhance the cutting performance.

This work aims to analyze the area underneath the nanoscratch track on micro and nano scale. During a nanoscratch test in the tribological contact, a flattening of the hard coating was observed by using scanning electron microscopy. The motivation for this paper was to contribute to a better understanding of this effect. It was assumed that the applied load as well as simultaneous thermally induced effects during nanoscratch test in short time lead to a melting of low melting phases within the superficial passive layer consisting of oxides. In order to verify this, the near-surface area underneath the nanoscratch track was analyzed by means of high resolution transmission electron microscopy. It is found, that the CrN/AlN loses its nanolaminate architecture in the near-surface area up to a depth of s approximate to 40 nm. Within this area, the crystallinity was significantly changed and amorphous fractions are identified by using fast fourier transformation patterns. Further, the results support the assumption that melting of low melting oxides in the passive layer occurs due to the superimposed mechanical and thermal load during nanoscratch test.

During the hard machining of powder metallurgical high-speed steel, finely dispersed carbides in the steel expose tools to both thermal and mechanical load. PVD hard coatings are used to protect the tools from wear, oxidation and diffusion processes. With regard to mechanical and thermal properties, (Ti,Al,Cr,Si)N hard coatings are advantageous compared to (Ti,Al)N due to their nanocomposite coating architecture. In addition to monolithic (Ti,Al,Cr,Si)N, a bilayer coating with a (Ti,Al,Cr,Si)ON top layer is deposited in order to investigate the influence of oxygen on the interaction with the workpiece during machining. The coatings were deposited in an industrial scale coating unit using a hybrid technology consisting of direct current and high power pulse magnetron sputtering (dcMS/HPPMS). The influence of the oxygen/nitrogen and the aluminum/titanium ratio on the coating as well as compound properties of indexable inserts made from cemented carbide were investigated. Furthermore, the oxidation and the phase stability were investigated. Finally, the coating systems were examined in cutting tests during which powder metallurgical high-speed steel was milled using 6 mm cemented carbide milling tools. The coatings show a fine crystalline morphology with a cubic crystal structure and a smooth surface. For oxynitride coatings, both hardness and resistance against plastic deformation show increased values compared to the nitride coatings. The additional oxygen might lead to a more brittle deformation behavior. The coating with an increased titanium/aluminum ratio shows, on the one hand, the best compound properties. On the other hand, its oxidation and phase stability are lower compared to the coatings with a lower ratio. In contrast to titanium, aluminum forms protective oxide layers which increase thermal resistance. In the cutting tests, the nitride coating shows a slightly higher tool life compared to the oxynitride coating. The tool life of the nitride coating with an increased titanium/aluminum ratio is significantly increased compared to the other coatings.

Referring to the expected increasing amount of aviation until the year 2030, energy and fuel efficiency as well as harmful emissions are of prime importance to the technological and ecological advancement of aircraft engines. Minimizing fuel consumption and improving energy efficiency of jet engines can be reached by increased turbine entry temperatures. However, the permitted combustion temperatures are restricted by material-dependent maximum service temperatures. Nowadays, yttria stabilized zirconia (YSZ) is commonly used as thermal barrier coating (TBC), only withstanding a permanent surface temperature of T similar to 1200 degrees C. In recent years, research projects have shown that multilayer systems might be a solution to withstand higher combustion temperatures. In order to assess this potential of multilayer systems, quadruple TBC consisting of 7 wt.% YSZ and La2Zr2O7 were deposited on INCONEL (R) 600 by electron beam physical vapor deposition. The quadruple TBC were fundamentally characterized with regard to their microstructure as well as their thermal conductivity lambda. Considering the requirements with regard to the application, the long term behavior under isothermal and thermal cycling load is of great importance. To classify this behavior, atmospheric annealing tests were performed at temperatures of T = 1200 degrees C and T = 1300 degrees C for t = 50 h as well as thermal cycling tests were conducted at a temperature of T = 1150 degrees C for N = 1000 cycles. The results of the quadruple layer TBC were compared to the prior investigated single and double layered TBC coatings consisting of YSZ or 7YSZ/La2Zr2O7. The investigations showed no major influence of multilayer architecture regarding the thermal conductivity lambda compared to conventional 7YSZ single layer architecture. Moreover, multilayer architecture leads to the increase of porosity inside the TBC. However, no strong correlation between porosity and thermal conductivity can be revealed. The analyses of the thermal cycled TBC show that TBC delamination is mainly caused by accelerated growth of thermally grown oxide and sintering effects. Furthermore, no improvement of the thermal cycling behavior due to quadruple multilayer architecture compared to 7YSZ single layer can be determined. The comparison of thermal cycling behavior regarding single, double and quadruple layer architecture emphasizes increased TBC lifetime of double layer TBC.

In today's mobility applications, efficiency is a key requirement. While in conventional mobility, increased efficiency contributes to reduce greenhouse gas emissions, in e-mobility every increase in efficiency translates also directly into increased battery range, which in turn contributes to reduced CO2 emission. Therefore, different approaches like the reduction of lubricant viscosities and the reduction of lubricant quantities towards minimum quantity lubrication are pursued. A promising approach to meet the increasing demands are (Cr,Al)N and triboactive (Cr,Al,Mo)N coatings. Within this work (Cr,Al)N and triboactive (Cr,Al,Mo)N coatings were investigated at a twin-disk test rig in highly-loaded rolling-sliding contacts. The coatings were deposited by means of cathodic arc evaporation (CAE) on the case hardened steel (AISI 5115) and tribologically investigated under minimum quantity (MQL) lubrication with a low viscosity, sulphur and phosphorous doped, polyalphaolefine oil. Compared to the uncoated steel, the coatings lead to a higher system stability, which can be characterized by a stable friction behavior, and wear reduction. Tribochemical interactions between coatings and lubricant were analyzed by means of Raman spectroscopy and reveal the in situ formation of MoS2. Furthermore, the coatings exhibit lower thermal conductivities compared to the uncoated steel, which might also affect friction reduction. The results show the high potential of (Cr,Al)N and triboactive (Cr,Al,Mo)N coatings under high tribological load.

The machining of powder metallurgical high-speed steel leads to thermal and mechanical loads which cause damages such as abrasive and adhesive wear as well as oxidation of the tool. Due to the high hardness and thermal resistance of hard coatings, their application on cutting tools is the state of the art. In order to improve the tool lifetime and the performance of the cutting process and to fulfill the increasing requirements in machining, the complex coating TiAlCrSiN was developed. The embedding of the nanocrystalline grains in an amorphous Si3N4 matrix is expected to result in advantageous properties in comparison to the coating TiAlCrN. The thermal resistance and elastic-plastic properties, for example, are enhanced. The coating deposition was conducted in an industrial coating unit using a hybrid process consisting of direct current Magnetron Sputtering and High Power Pulsed Magnetron Sputtering (dcMS/HPPMS). By using this hybrid process, the advantages of HPPMS, such as a dense morphology and high indentation hardness, are combined with the higher deposition rate of dcMS. In this work, the influence of the substrate bias and the pulse frequency of the HPPMS cathodes during the hybrid process are observed. The coating properties are only slightly affected by variations in the process parameters. Transmission electron microscopy investigations reveal the nanocrystalline microstructure of the coating. The compound properties between the different coatings and the indexable inserts made of tungsten carbide were improved by reducing the substrate bias. Furthermore, the coatings are tested by milling the powder metallurgically produced high-speed steel 1.3345. The milling tool coated with an increased frequency and a reduced substrate bias shows the highest tool lifetime during the cutting tests.

Efficiency during operation is besides reliability and cost effective production one of the most important demands on machines and components. Especially within the automotive sector, components need to fulfill these requirements. Since the demands for high efficiency and reliability cannot be met solely by typical base materials such as case hardened steels, physical vapor deposition (PVD) coatings for the application on highly loaded components gain increasing importance. A possible approach to reduce friction and wear in tribological systems are triboactive and tribocatalytic coatings which contain triboactive elements such as Mo and Cu which can interact with lubricants and lead to the formation of friction and wear reducing tribochemical reaction layers. Besides coating development, also the design of lubricants is in the focus of research activities to reach friction reductions. Therefore, increasing interest gains towards low viscosity lubricants e.g. for e-mobility applications, since reduced friction would lead to extended range. Within the current work, triboactive (Cr,Al,Mo)N and (Cr,Al,Cu)N, (Cr,Al,Mo,Cu)N coatings were deposited by means of cathodic arc evaporation (Arc PVD) in an industrial scale coating unit. The contents of Mo and Cu were varied. As substrate material the case hardened gear steel AISI 5115 (16MnCr5E) was used. The effects of Mo and Cu on the phase formation were investigated by means of X-ray diffraction (XRD). Analysis of the mechanical properties was conducted by nanoindentation (NI) measurements. Tribological behavior of the coatings was analyzed under continuous sliding conditions in pin on disc (PoD) tribometer under minimum quantity lubrication with lubricant amounts of V = 0.05 ml at a temperature T = 80 degrees C. As lubricants, a low viscosity lubrication oil and a conventional mineral oil were used. Both lubricants contained sulphur and phosphor (S-P) or sulphur (S) additives. In order to investigate the influence of the counter part material on the tribological behavior, inert Si3N4 balls and 100Cr6 steel balls were used. Initial Hertzian contact pressures were set to p(H) approximate to 1400 MPa and p(H) approximate to 1600 MPa, respectively. Wear was analyzed by confocal laserscanning microscopy (CLSM). Tribochemical interactions between the coatings and lubricants were studied by Raman spectroscopy. It was found that tribochemical interactions between Mo of the coatings and S of the lubricants can lead to the in situ formation of MoS2 in tribological contact.

Diamond-like carbon (DLC) coatings are nowadays successfully applied on industrial components like pistons, piston rings and bearings in lubricated tribological contacts due to friction and wear reducing effects. In contradiction thereto, todays lubricants and additives are designed for tribological steel/steel contacts, whereby the knowledge on tribochemical layer formation on steel surfaces is comprehensive in contrast to the physical-chemical interactions between diamond-like carbon coatings, lubricants and additives. Therefore the formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a zirconium modified diamond-like carbon coating a-C : H : Zr (ZrCg) in lubricated tribological contacts were analyzed by means of pin-on-disc (PoD) tribometer by varying the distances from s = 200 m-3,000 m under boundary and mixed friction conditions at T = 90 degrees C and a contact pressure p = 1,300 MPa regarding the application of diamond-like carbon coatings on gears. The base lubricant poly-alpha-olefin (PAO) was formulated using the anti-wear (AW) and extreme pressure (EP) additive zinc dialkyldithiophosphate (ZnDTP) and the friction modifier (FM) additive molybdenum dialkyldithiophosphate (MoDTP). The chemical composition of the tribochemical reaction layers by means of and Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) as well as for the thickness differ significantly by varying the additivation.

Nanocomposite coatings such as (Ti, Al, Si)N have been demonstrated as promising candidates for the use as protection against solid particle erosion for compressor blades. Typically, nanocomposite (Ti, Al, Si)N coatings are deposited by different physical vapor deposition (PVD) techniques. However, the relatively low coating thickness up to a few micrometers due to low deposition rates leads to a limited lifetime of the coatings under erosive particle bombardment. In this study, the deposition of a nanocomposite (Ti, Al, Si)N coating was performed by a hollow cathode gas flow sputtering method, the high-speed physical vapor deposition, which enables the high-rate deposition of thick coatings. Morphology and microstructure of the coating were investigated via scanning electron microscopy and transmission electron microscopy, respectively. Tribological characterization by impact tests and erosion tests demonstrates that the nanocomposite (Ti, Al, Si)N coated sample reveals a promising resistance against impact loads and the solid particle erosion. Summarily, nanocomposite (Ti, Al, Si)N coatings deposited by the high-speed physical vapor deposition provide a high potential for the erosion protection of compressor blades.

There has been remarkable progress in the recent years on development of thin hard chromium based coatings using physical vapor deposition (PVD) for numerous technical fields, e.g. plastic processing. An improved interaction can be achieved between the coating/substrate compounds and the molten plastic using (Cr,Al)ON compared to (Cr,Al)N. Therefore, the (Cr,Al)ON can extend the service life of tools and components by increasing their corrosion and wear resistance in plastic processing. This highlights the necessity of a detailed understanding of this coating. Within this paper, coatings of type (Cr,Al)ON were deposited on tool steel substrate AISI 420 (X42Cr13, 1.2083) in an industrial scale coating unit through three different technologies, namely, direct current magnetron sputtering (dcMS), high power pulse magnetron sputtering (HPPMS) and a hybrid technology, including dcMS and HPPMS. The influence of oxygen on properties such as indentation hardness and modulus was studied using oxynitrides having different oxygen contents. Comprehensive investigations were performed by electron probe micro analyses (EPMA), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Based on the results, there exists no significant dependency of aluminum content in the coating on oxygen content in the reactive gas. The coatings deposited by dcMS have the lowest ratios of Al/Cr, while the HPPMS coatings show the highest ratios. This might be attributed to the decreasing deposition rate of chromium by increasing ion energy. The coating deposited by HPPMS has a significantly higher oxygen content revealing more dissociation of oxygen than nitrogen at higher ion energies. The analyses depict the formation of only cubic phases. The anion/cation ratio delta/xi increases by increasing oxygen content. Potential reasons for the ratios of delta/xi > 1 might be attributed to the formation of cubic (Cr,Al)2 + theta O3 phases, the enrichment of oxygen at the grain boundaries or the cation vacancies in the cubic metal lattice.

Chromium-based hard coatings deposited using physical vapor deposition are commonly applied protective coatings in several technical applications such as cutting or plastics processing. Particularly enhanced oxidation resistance can be achieved using the oxy-nitride coating system (Cr,Al)ON. Although several studies on (Cr,Al)ON have been conducted, details on the incorporation of oxygen into the coating system are still subject of research. This will be discussed in the present paper through three mechanisms. Considering the (Cr,Al)N with a cubic structure, oxygen can be interstitially stored in the lattice. Here, the nitrogen anions are replaced by the oxygen anions leading to the formation of metal vacancies. In addition to the cubic (Cr,Al)ON, other phases can be formed in the coating, e.g. cubic phases of the type (Cr,Al)(2+theta)O-3 with theta <= 1 or corundum phase alpha-(Cr,Al)(2)O-3. In both latter phases, nitrogen can be additionally dissolved in the phases. Moreover, oxygen might segregate preferably at column boundaries. This phenomenon has hardly been explored. Therefore, the column boundaries of a (Cr,Al)ON coating are investigated in this work using transmission electron microscopy. The coating deposition was conducted in an industrial scale coating unit using a hybrid technology consisting of direct current and high power pulse magnetron sputtering. The results suggest that higher oxygen concentrations can be detected at column boundaries. Oxygen-rich column boundaries would contribute to explaining most recently studied phenomena in thin hard chromium-based coatings. Among such phenomena are the column separation manifested by a reduced cohesion between microstructural columns or the grain boundary sliding.

The increasing demand for corrosion and wear reduction in modern tribological systems places high requirements on hard coatings deposited by physical vapor deposition (PVD) technology in numerous technical applications e.g., plastic processing, die casting or machining. One possible approach to withstanding the excessive wear is coating of tools with PVD hard coatings of the system Cr-Al-O-N. Each of the constituent elements can provide the coating with particular characteristics in point of its performance under different loading conditions. Therefore, the ongoing improvement in modern surface engineering requires comprehensive insights into the elastic-plastic deformation and cracking behavior of such coatings. For this purpose, several modifications and extensions of established experiments are required to overcome the limitations involved in characterization of thin hard coatings e.g., as a result of the μm ranges. In the presented work, three coatings CrN, (Cr,Al)N and (Cr,Al)ON deposited on quenched and tempered AISI 420 steel substrate were investigated. All coating systems were deposited through a hybrid technology, consisting of direct current and high power pulse magnetron sputtering (dcMS/HPPMS). The deformation and cracking behavior of the coatings and coating/substrate compounds were studied through application of static loadings by nanoindentation and Rockwell tests as well as dynamic loading conditions using nanoscratch tests. Complementary quantitative investigations were performed by means of depth profiling using confocal laser scanning microscopy (CLSM). Qualitative analyses of Rockwell imprints and nanoscratch tracks were conducted through scanning electron microscopy (SEM). Based on the results, precise analyses of nanoindentation force-displacement curves can improve the understanding about the possible crack formation in the coatings. Compared to (the binary) CrN, the ternary coating system (Cr,Al)N exhibits more promising characteristics in point of elastic-plastic deformation behavior and crack resistance. The crack resistance decreases through incorporation of oxygen into the ternary nitride and deposition of quaternary oxynitrides (Cr,Al)ON. Such character of oxynitrides can be overseen taking into consideration only the static loadings and therefore, applying of the both static and dynamic loading conditions are required to gain precise knowledge on the deformation and cracking behavior of thin hard coatings.