Cathodic Arc Evaporation Method Research Articles

Cavitation erosion resistance parameter of hard CAVD coatings

Nowadays the most machining tools are coated with hard coatings to prolong their lifetime and to improve their working efficiency. They are very often used for high wear applications, where they are subjected to cyclic impact loading. Main benefits of hard coatings are based on the combination of high hardness and toughness, properties that are especially important in the conditions of dynamic impact wear when high cyclic local loading is the main cause of coating degradation. A cavitation test can be a useful tool for studies of plastic deformation, crack initiation and propagation in thin hard coatings. Cavitation damage is caused by repeating action of imploding cavitation bubbles in the vicinity of solid surface. Because TiN and Cr–N coatings are the most popular coatings for commercial applications, their cavitation erosion resistance were tested. TiN and Cr–N coatings with various thicknesses were deposited on stainless steel, by means of the cathodic arc evaporation (CAVD) method at various temperatures and bias voltages. All tests were performed in the same cavitation conditions in the cavitation chamber with a system of barricades. Obtained results have showed very good correlation between the mass loss and the new parameter. Analysis of degradation mechanism of thin nanocrystalline coatings under the impact degradation results in the obtainment of a new parameter to assess the resistance of hard coating against cavitation. The cavitation tests showed that plastic properties and adhesion play the main role in the coatings resistance, as well as the structure of a given material and its thermal properties.

An experimental parameter of cavitation erosion resistance for TiN coatings

A series of cavitation erosion tests were carried out to investigate the resistance of the TiN coatings against cavitation action. The TiN coatings were deposited at various deposition parameters on austenitic stainless steel, X6CrNiTi18-10, with various coating thicknesses by means of the cathodic arc evaporation method (CAVD). Investigations were performed in a cavitation tunnel with a slot cavitator. The estimation of cavitation resistance of the TiN coatings was performed on the basis of the incubation period and the mass loss. The investigations show that coating hardness, Young's modulus, adhesion and coating thickness have an influence on coating endurance to cavitation degradation. The parameter H·LC2/E·h1/2 shows very good fitting to data points (R2 = 0.9707). Along with the increase of the H·LC2/E·h1/2 parameter the mass loss decreases indicating a continuous improvement in the cavitation erosion resistance.

The new parameter to assess cavitation erosion resistance of hard PVD coatings

Most machinery elements are coated with hard coatings to prolong their lifetime and to improve working efficiency. Cavitation test was used as a tool for studies of dynamic impact degradation. Ti- and Cr-based coatings were chosen for investigations. The TiN and Cr–N coatings with various thicknesses were deposited on stainless steel by means of the cathodic arc evaporation method at various deposition parameters. Tests were performed in the cavitation chamber with a system of barricades. Nearly all the TiN and Cr–N coatings have undergone micro-undulation. The first cohesive fractures have occurred on top of the micro-folding and at delamination spots. The analysis of degradation mechanism of thin hard coatings under repeated impact loading has resulted in deriving a new empirical parameter suitable for description of the hard coating cavitation resistance. The derived parameter is proportional to the plasticity index, H/ E (defined as ratio of hardness, H, and Young’s modulus, E), adhesion force, L C2, ratio of thermal conductivity of the coating to that of the substrate, and inversely proportional to the number of phases in the coating phase composition, the ratio of the thermal expansion of the coatings to that of the substrate and the square root of the coating thickness. The new endurance parameter shows good correlation with the mass loss of all the tested hard coatings indicating a continuous improvement in the erosion resistance with the increase of the new parameter.

An approach to evaluate the resistance of hard coatings to shock loading

Nowadays hard coatings are widely used to prolong lifetime of most tools and machinery elements and to improve their working efficiency. The main benefits of hard coating are based on the combination of high hardness and toughness: properties that are especially important in conditions of dynamic impact wear, when high cyclic local loading is the main cause of coating degradation. Cavitation test seems to be a useful tool for analyses of deformation, crack initiation and their propagation in hard coatings. The TiN and Cr–N coatings were deposited on steel substrate by means of the cathodic arc evaporation method at various temperatures and bias voltage, and at various thicknesses. The coatings were tested in a cavitation tunnel with a system of barricades to determine the parameters describing coating properties related to the dynamic loading resistance and to explain the failure mechanism of hard coatings under dynamic loading conditions. The analysis of degradation mechanism of thin hard coatings under repeated impact loading has resulted in deriving a new empirical parameter suitable for description of the hard coating cavitation resistance. The derived parameter is proportional to the plasticity index, H/E, (defined as ratio of hardness, H, and Young's modulus, E), adhesion force, LC2, ratio of thermal conductivity of the coating to that of the substrate, and inversely proportional to the number of phases in the coating phase composition, the ratio of the thermal expansion of the coatings to that of the substrate and the coating thickness. The cumulative mass loss determined in the tests shows very good correlation with the new parameter.

Hard CrCN/CrN multilayer coatings for tribological applications

Hard coatings were deposited using a cathodic arc evaporation method. The results of investigations of multilayer CrCN/CrN coatings are presented in this article. The microstructure and crystallinity of films have been investigated using X-ray diffraction (XRD). The composition was determined with energy dispersive spectroscopy (EDS). The adhesion of films was estimated on the basis of an analysis of scratch-test results. The hardness and tribological properties of films deposited on hardened and tempered HSS substrates were also investigated. The tribological tests were carried out in a pin-on-disc geometry. The influence of a normal load, sliding speed and a counterpart material on the friction coefficient and the specific wear rate of the coatings were studied. The counterparts were made of HSS and four types of wood: oak, beech, spruce and pine. The hardness and adhesion of multilayer CrCN/CrN coatings are respectively 25 GPa and 120 N.

Investigation of ZrN Hard Coatings Obtained by Cathodic Arc Evaporation

Zirconium nitrides (ZrN) coatings have shown better quality in comparison to titanium nitrides (TiN) ones regarding the application in the mechanical processing of aluminum and titanium alloys. This work presents the results from investigation on properties of ZrN-based coatings intended for industrial application. The ZrN and ZrTiN hard coatings in a thickness of (3 5) m were obtained on stainless steel substrates by cathodic arc evaporation method. The coating hardness in the range of 25-32 GPa was evaluated using the Vickers measurement technique. The coating properties were studied in relation to the surface morphology by Atomic force microscopy (AFM) and Scanning electron microscopy (SEM). The analyses showed that the number and size of the macroparticles decrease when N2 pressure increases in the deposition chamber. X-ray diffraction analysis (XRD) was performed to identify the crystallographic structure, preferred orientation and stress of the ZrN coatings.

The influence of TiN coatings properties on cavitation erosion resistance

A series of cavitation erosion tests was carried out to investigate the influence of the TiN coating properties on cavitation resistance. The TiN coatings were deposited at various deposition parameters on austenitic stainless steel, X6CrNiTi18-10, by means of the cathodic arc evaporation method. Investigations were performed in a cavitation tunnel with a slot cavitator. The estimated cavitation resistance parameters were the incubation period and the mass loss. The degradation process of the TiN coatings originates mainly from the plastic deformation of the steel substrate – hard coating system, visible in the microscope as “micro-folding” of the surface. The results of the investigation indicated that the main factors responsible for the cavitation resistance of the steel substrate / hard coating system were the H/ E parameter and the coating adhesion. The H/ E parameter had an influence on the mass loss while the critical load L C2 was found to have an influence on the mass loss and on the incubation period. Moreover, a good correlation between roughness parameters measured after cavitation test and adhesion was found.

Cavitation resistance of Cr–N coatings deposited on austenitic stainless steel at various temperatures

Cr–N coatings were deposited on austenitic stainless steel, X6CrNiTi18-10, by means of the cathodic arc evaporation method at three substrate temperatures: 200 °C, 350 °C and 500 °C. All coatings were found to have a composition of Cr(N), CrN and Cr 2N. The substrate temperature was found to have an influence on the hardness and Young's modulus of the Cr–N coatings. The investigation of nanocrystalline Cr–N coatings resistance to cavitation was performed in a cavitation tunnel with a slot cavitator and tap water as the medium. The estimated cavitation resistance parameters of the coatings were the incubation period of damage and total mass loss. It was found that the optimal coating cavitation resistance was deposited at 500 °C. The incubation period for the 500 °C deposition coating was the same as that of the uncoated X6CrNiTi18-10 steel, but the total mass loss was significantly lower than on the uncoated specimen. The scanning electron microscope analysis indicated that the damage process of the Cr–N coating mainly originates from the plastic deformation of the steel substrate–hard coating system, which appears by “micro-folding” of the surface. An increase of tensile stresses at the top of micro-folds initiates micro-cracks and delamination of Cr–N coating. The results of the investigation and the analysis indicate that the factors mainly responsible for cavitation resistance of the steel substrate/hard coating system are resistant to plastic deformation of the total system and coating adhesion.

Arc-evaporated CrN, CrN and CrCN coatings

The results of investigations of some tribological properties of chromium nitride, carbonitride and carbide films, prepared by cathodic arc-evaporation method (CAE) are presented in this article. The chemical composition of films was determined by the WDXs and EDXs. The different carbon content was obtained by using nitrogen and acetylene mixtures of various concentrations as the deposition atmosphere. The carbon content was ranging from 0 to 53at.%. The adhesion of CrCN films was estimated from the analysis of scratch-test results comprising tangential (friction) force, acoustic emission and morphology of scratch surface. The films showed very good adhesion to steel substrates, expressed by Lc (critical load) value, as high as 90N for carbon free films. The Lc decreased slightly as the carbon content increased. The hardness of films was investigated as a function of carbon content and was estimated by Jönsson–Hogmark method. The Lc value and hardness seem to be correlated in the same way with carbon content. The highest hardness (30GPa) was obtained for CrN films, while carbon rich films (CrC) showed hardness at the level of 20GPa. The tribological tests were performed in the ball-on-disk geometry in room air under the load of 1N and 10N. The wear rate of investigated films increased with carbon content above 20at.%. The maximum value of the friction coefficient was 0.55, the same as for CrN films. It decreased to 0.33 as the carbon content increased.

Investigation concerning the cavitation resistance of TiN coatings deposited on austenitic stainless steel at various temperatures

TiN coatings were deposited on austenitic stainless steel, X6CrNiTi18-10, by means of the cathodic arc evaporation method at three different substrate temperature: 200 °C, 350 °C and 500 °C. All coatings were found to have strong (1 1 1) crystallographic orientation and fine crystalline structure of the δ-TiN phase. The substrate temperature was found to have an influence on the hardness and Young's modulus of the TiN coatings. Investigation of nanocrystalline TiN coatings resistance to cavitation was performed in a cavitation tunnel with a slot cavitator and tap water as the medium. The estimated cavitation resistance parameters of the coatings were the incubation period of damage, and total mass loss. It was found that the optimal coating cavitation resistance was deposition at 350 °C. The incubation period was the longest and the total mass loss was the least for deposition at 350 °C. The incubation period for the 350 °C deposition coating was approximately 100% longer than that of the uncoated X6CrNiTi18-10 steel and the total mass loss was significantly lower than that of the uncoated specimen. The scanning electron microscope analysis indicated that the damage process of the TiN coating mainly originates from the plastic deformation of the steel substrate– hard coating system, which appears by “micro-folding” of the surface. An increase of tensile stresses at the tops of micro-folds initates microcracks and delamination of TiN coating. The results of the investigation and the analysis indicate that the factors mainly responsible for cavitation resistance of the steel substrate/ hard coating system are resistance to plastic deformation of the total system and coating adhesion.

Thermal stability of Cr1−xAlxSiyN coatings with medium and high aluminium content prepared by arc evaporation

ABSTRACTThe thermal stability of Cr1−xAlxN and Cr1−xAlxSiyN nanocomposite coatings with different composition x, Si content, and phase structure has been investigated. The coatings were deposited in an industrial unit by the cathodic arc evaporation method, using rotating cylindrical cathodes. Further sets of coated WC/Co plates were subjected to an annealing step in a forming gas (92% N2 / 8% H2) atmosphere for several hours at a constant temperature (maximum 1000°C). Chemical composition, microstructure and mechanical properties of the coatings were investigated by the RBS, XRD, TEM, SEM, XPS and nanoindentation techniques.As-deposited Cr1−xAlxSiyN coatings with Al contents x in the range of 0.4 ≤ x ≤ 0.6 showed a single-phase cubic CrAlN structure and a maximum hardness of 38 GPa. With increasing the Al content to x = 0.95 – 0.96, two-phase films consisting of hexagonal AlN and cubic CrAlN structure with hardness of about 31 GPa were obtained. The hardness of Cr1−xAlxSiyN coatings increases during annealing at temperatures in the range of 800 – 1000°C by about 1 – 4 GPa, even though the residual compressive stress in the coatings was found to relax considerably during this procedure. The addition of Si into Cr1−xAlxN delays the appearance of hcp-AlN and thereby improves the thermal stability of the coatings.