Physical Vapor Deposition Magnetron Sputtering Research Articles

Statistical optimization and fretting fatigue study of Zr/ZrO2 nanotubular array coating on Ti–6Al–4V

Herein, the fretting fatigue behavior of zirconium nanotube arrays on the surface of Ti–6Al–4V is studied. Initially, a thin film of pure zirconium (Zr) was deposited onto a Ti–6Al–4V substrate using physical vapor deposition (PVD) magnetron sputtering for the primary layer at varying DC power, temperature and substrate bias voltage values. To obtain higher adhesion strength, the Taguchi optimization method was used to estimate the optimum coating parameters, while a Pareto ANOVA was employed to determine the significant parameters. The strongest coating adhesion, as determined by a scratch force test, was achieved at 300W DC power, 200°C and a 75V bias voltage. Consequently, nanotubes were produced via Zr anodization in an NH4F electrolyte solution (95 glycerol:5 water) at different times and at a constant potential of 60V (second layer). The fretting fatigue behavior of anodized samples annealed at 400°C and 800°C was investigated. The results indicate that the fretting fatigue life of the ZrO2 nanotube-coated samples was significantly improved at low and high cyclic fatigue at an annealing temperature of 400°C compared to the uncoated samples.

Multilayer thin film CrN coating on aerospace AL7075-T6 alloy for surface integrity enhancement

Chromium nitride (CrN) coating has emerged as a new alternative in machining applications. CrN has good thermal stability, low deposition temperature, and excellent wear and corrosion resistance. However, no precise informa- tion exists yet regarding the ideal coating parameter condi- tions that lead to higher surface integrity. For this reason, an optimization study is desired—a study on the parameters of CrN coating on aerospace Al7075-T6 alloy using physical vapor deposition magnetron sputtering. The present research work investigates the effects of temperature as well as nitro- gen flow rate and DC power on coated samples' surface hardness, adhesion, surface roughness, and microstructure. To carry out the investigation, the Taguchi optimization meth- od with L16 (3 4 ) orthogonal array was applied. However, to obtain optimum parameters for superior surface integrity, signal/noise (S/N) response analysis method was employed. Finally, confirmation tests with the best parameter combina- tions attained in the optimization process were carried out to demonstrate the progress made. Ultimately, surface hardness of coated Al7075-T6 was enhanced by 15.33 %, adhesion by 24.3 %, and surface roughness by 7.22 %.

Modeling of TiN Coating Thickness Using ANFIS

In this paper, an approach in predicting thickness of Titanium Aluminum Nitrite (TiN) coatings using Adaptive Network Based Fuzzy Inference System (ANFIS) is implemented. The TiN coatings were coated on tungsten carbide (WC) using Physical Vapor Deposition (PVD) magnetron sputtering process. The N2 pressure, argon pressure and turntable speed were selected as the input parameters and the coating thickness as an output of the process. Response Surface Methodology (RSM) was used to design the matrix in collecting the experimental data. In the ANFIS structure, three bell shapes were used as input membership function (MFs). The collected experimental data was used to train the ANFIS model. Then, the ANFIS model was validated with confirmatory test data and compared with other prediction models in terms of the root mean square error (RMSE), residual error and prediction accuracy. The result indicated that the developed ANFIS model result was the lowest RMSE7 and average residual error, besides the highest in prediction accuracy compared to the other models. The result also indicated that the limited experimental data could be used in training the ANFIS model and resulting accurate predictive result.

Novel experimental set-up to investigate the wear of coatings for sheet metal forming tools

The use of hard coatings to improve the service-life of forming tools has increased significantly in metalforming processes, both for bulk- and sheet- metal applications. However, while the knowledge on the most relevant coating technologies, namely the Physical Vapour Deposition (PVD) and Chemical Vapour Deposition (CVD), has been developed and improved, the approaches to select the coatings for a specific forming operation still remain not well established, being mainly based on trial and error experiences. Finite Element Method (FEM) analyses may represent an effective support in the coating selection thanks to the possibility of investigating the influence of the different process parameters, but the need of testing procedures and reliable models to describe the mechanical and tribological phenomena at the interface between the dies and the workpiece is still relevant. The paper presents a novel experimental set-up for the evaluation of the wear resistance of coated tools in sheet metal forming operations. A progressive stamping process was taken as reference case and analysed by numerical simulation in order to evaluate contact pressures and sliding speed at tools-blank interface. The diamond-like-carbon coating a-C:H:Ti was chosen as reference and deposited by PVD magnetron sputtering technique. The novel set up was designed and tested by using the parameters obtained from the numerical simulation. The results showed a good correlation with tribological and mechanical stresses applied on the reference industrial case, allowing the evaluation of the coating performances.

A fuzzy logic predictive model for better surface roughness of Ti–TiN coating on AL7075-T6 alloy for longer fretting fatigue life

In this study, the fretting fatigue resistance of AL7075-T6 alloy is investigated using surface treatment Ti–TiN multilayer coating by physical vapor deposition (PVD) magnetron sputtering technique. A fuzzy logic model was established to forecast the surface roughness of Ti–TiN coating on AL7075-T6 with respect to changes in the input process parameters of DC power, temperature, DC bias voltage, and nitrogen flow rate. The results indicate an agreement between the fuzzy model and experimental results with 95.349% accuracy. The fretting fatigue lives of Ti–TiN-coated specimens with the lowest surface roughness resulting from fuzzy logic were enhanced by 18% at low cyclic fatigue, while at high cyclic fatigue the result was reversed.

Mechanical Property Enhancement of Ti-6Al-4V by Multilayer Thin Solid Film Ti/TiO2 Nanotubular Array Coating for Biomedical Application

With the intention of improving the mechanical properties of Ti-6Al-4V, samples were first coated with pure titanium using the physical vapor deposition (PVD) magnetron sputtering technique. The Taguchi optimization method was used to attain a higher coating on substrate adhesion. Second, pure titanium-coated samples with higher adhesion were anodized to generate TiO2 nanotubes. Next, the TiO2-coated specimens were heat treated at annealing temperatures of 753.15 K and 923.15 K (480 °C and 650 °C). The XRD results indicate that the varying heat treatment temperatures produced different phases, namely, anatase [753.15 K (480 °C)] and rutile [923.15 K (650 °C)]. Finally, the coated samples’ mechanical properties (surface hardness, adhesion, and fretting fatigue life) were investigated. The fretting fatigue lives of TiO2-coated specimens at 753.15 K and 923.15 K (480 °C and 650 °C) annealing temperatures were significantly enhanced compared to uncoated samples at low and high cyclic fatigue. The results also indicate that TiO2-coated samples heat treated at an annealing temperature of 753.15 K (480 °C) (anatase phase) are more suitable for increasing fretting fatigue life at high cyclic fatigue (HCF), while at low cyclic fatigue, the annealing temperature of 923.15 K (650 °C) seemed to be more appropriate. The fretting fatigue life enhancement of thin-film TiO2 nanotubular array-coated Ti-6Al-4V is due to the ceramic nature of TiO2 which produces a hard surface as well as a lower coefficient of friction of the TiO2 nanotube surface that decreases the fretting between contacting components, namely, the sample and friction pad surfaces.

Experimental Evaluation of Innovative Tools for Ti-6Al-4V Turning

Titanium alloys, mainly because of their poor thermal conductivity, need to be cut at relatively low cutting speeds, with obvious negative consequences on the profitability of machining. An important amount of research activities has been done in order to increase productivity in titanium machining operations: high performance coatings and innovative technologies to improve inserts resistance to wear represent promising solutions. In this work, the cutting performance in Ti6Al4V rough turning of an innovative TiAlN coating obtained by Physical Vapor Deposition (PVD) magnetron sputtering and the effects of a Deep Cryogenic Treatment (DCT) have been experimentally investigated and a statistical analysis of the results has been performed. Typical commercially available inserts (TiAlN-AlCrO coated) have been used as a benchmark. Preliminary hardness and thermal conductivity measurements tests have been performed on the three types of tool to determine the differences caused by the different coatings and thermal treatment. The experiments have been conducted using a full factorial design in order to statistically evaluate, using ANOVA, the significance of the input factors on the process most interesting outputs. tool life and other variables of interest with different process parameters. The considered input factors are type of insert, cutting speed and feed rate. The analysed responses are average flank wear, surface roughness, cutting forces, coefficient of friction and chip morphology. The results show that even if friction coefficients are lower for standard tools, innovative inserts exhibit a higher resistance to wear. Taylor’s law parameters of PVD coated tools, with and without DCT have been determined, clearly showing that cryogenically treated tools present higher resistance at higher cutting speeds, mainly due to their superior hardness. In conclusion, it appears that relevant improvements of productivity or profitability of titanium turning can be obtained if an advanced PVD coating, deposited by magnetron sputtering is used on tungsten carbide inserts and if deep cryogenic of the inserts is performed afterwards.

Fretting fatigue life evaluation of multilayer Cr–CrN-coated Al7075-T6 with higher adhesion strength—fuzzy logic approach

In this research work, an experimental evaluation was conducted to explore the fretting fatigue life of multilayer Cr–CrN-coated AL7075-T6 alloy specimens with higher adhesion strength to substrate as the coating adhesion strength is one of the most critical issues in magnetron sputtering technique. Physical vapor deposition (PVD) magnetron sputtering technique was used for coating purpose, and a fuzzy rule-based system was established to investigate how to achieve higher adhesion of Cr–CrN coating on AL7075-T6 with respect to changes in input process parameters, direct current power, nitrogen flow rate, and temperature. Close assent was obtained between the experimental results and fuzzy model predicted values. Experimental result analysis was performed with Pareto–ANOVA variance as an alternative analysis. The fretting fatigue lives of coated AL7075-T6 alloy were improved 70 % and 22 % at high and low cyclic fatigue, respectively, compared with uncoated specimens.

Flow curve determination on dc-MS and HPPMS CrAlN coatings

In this paper, a new method for determining flow curves of thin coatings is tested on the basis of chromium aluminum nitride coatings deposited by direct current and high power pulsed magnetron sputtering physical vapour deposition with a wide range of chemical composition. The flow curves have been determined using the nanoindentation technique with a spherical indenter combined with analytical methods and finite element simulation. Extensive analyses of the FEM simulation also examine the possible influence of the substrate material on the measured flow curves. The results show that different coating flow behaviour have been characterized with this method which can be correlated with material phase appearance in the coating. Suggestions to completely eliminate the substrate's influence in experiment or simulation are made.

Tribological Investigation of Nano Composite Coated Titanium Alloy Surfaces under Unidirectional Sliding

Industrial application of sliding components required to improve the tribological properties by increasing the surface hardness, friction and wear resistance. Modern modification of surface layers for friction applications combines surface texturing and filling of textured layers by wear resistant coatings of various compositions to improve its functional aspect and enhanced service life. Texturing of contact surfaces has a remarkable influence on their tribological properties, especially in the effect of wear and friction. This work proposes the coating of nano sized Titanium Aluminum Nitride (TiAlN) by Magnetron Sputtering-Physical Vapour Deposition (PVD) on the Titanium alloy (6Al-4V) substrate and study the performance of the coated surfaces by pin on disc tribometer. Two kinds of substrates were prepared one is the lapped surface and the other one is the textured surface by Laser beam machining. The Tribological performance of the wear resistant coatings on lapped and textured surfaces was experimentally investigated under various normal load conditions and the results were compared. Critical parameters such as friction coefficient, wear rate, wear volume, wear morphology and micro wear mechanism were investigated in this work. The coating surfaces and wear scars were evaluated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX). The results showed that the TiAlN coating on textured surfaces exhibited lower friction coefficient and wear rate than the TiAlN coating on lapped surfaces under same testing conditions.

Mechanical and Tribological Characterization of TiB2 Thin Films

Titanium Diboride (TiB2) presents high mechanical and physical properties. Some wear studies were also carried out in order to evaluate its tribological properties. One of the most popular wear tests for thin films is the ball-cratering configuration. This work was focused on the study of the tribological properties of TiB2 thin films using micro-abrasion tests and following the BS EN 1071-6: 2007 standard. Due to high hardness usually patented by these films, diamond was selected as abrasive on micro-abrasion tests. Micro-abrasion wear tests were performed under five different durations, using the same normal load, speed rotation and ball. Films were deposited by unbalanced magnetron sputtering Physical Vapour Deposition (PVD) technique using TiB2 targets. TiB2 films were characterized using different methods as Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Electron Probe Micro-Analyser (EPMA), Ultra Micro Hardness and Scratch-test Analysis, allowing to confirm that TiB2 presents adequate mechanical and physical properties. Ratio between hardness (coating and abrasive particles), wear resistance and wear coefficient were studied, showing that TiB2 films shows excellent properties for tribological applications.

Structural and Mechanical Characterization of Duplex Multilayer Coatings Deposited onto H13 Tool Steel

Quenched and tempered H13 tool steel was plasma nitrided and Physical Vapour Deposition (PVD) coated in a hybrid reactor aiming to obtain a TiN/TiC multilayer coating deposited on a plasma nitrided substrate, with a more gentle transition of elastic-plastic properties between the outermost layer of the coating and the substrate. Duplex treatment (plasma nitriding and PVD coating) was carried out in a hybrid reactor. Plasma nitriding preceded the DC triode magnetron sputtering PVD process, conducted inside the same chamber, using CH 4 and N 2 as reactive gases. Multilayer TiN/TiC coatings deposited on a nitrided H13 substrate were obtained. The multilayer coating was composed by a first Ti interlayer to grant adhesion, followed by a second 18.4 at% C TiC layer with a cF8 NaCl type unit cell, then a 41.9 at% N TiN layer and finally an outermost 32.3 at% C TiC layer with the same cF8 NaCl type unit cell. The multilayer coating showed a gentle transition of elastic-plastic properties assessed by the H/E * and the H 3 /E *2 ratios and the elastic recovery as a function of the distance from the surface of the specimen. The adhesion of the multilayered coating to the substrate was greater in the case of the duplex coated specimen as compared to the non duplex treated H13 steel.

Indium tin oxide coatings properties as a function of the deposition atmosphere

Indium tin oxide coatings were deposited by magnetron sputtering physical vapour deposition under different atmospheres. Microstructural, electrical, and optical properties were measured, finding a correlation among properties and process parameters. Texture analyses carried out by X-ray diffraction showed that films microstructure depended by the oxygen content in the deposition vessel: high values of the oxygen content (e.g., 5%) caused the film to grow along the <111> orientation; under pure Ar, the grains grew along the <100> orientation. Intermediate values of the oxygen content caused the growth of two families of grains, respectively oriented along the <111> and the <100> directions.

Tribological Behaviour of PVD Coatings for Sheet Metal Forming Tools: Laboratory and Industrial Evaluation

In the last decades, Physical Vapour Deposition (PVD) and Chemical Vapour Deposition (CVD) processes have been significantly improved and optimized for the applications on dies for sheet metal forming processes. However, due to the different contact conditions at dies-blank interfaces, and the wide range of applied contact pressures, the selection of the correct coating may be still affected by trials-and-error approaches. Although many methods to evaluate the tribological performances of such coatings can be found in scientific literature, they often suffer of limitations in reproducing the interface conditions typical of industrial processes. The objective of the present research work is to investigate the tribological behaviour of two coatings deposited by PVD magnetron sputtering technique. Both investigations in laboratory and industrial conditions were performed: the former to evaluate their tribological characteristics, the latter to test the performances of coatings in production lines. The results, in terms of wear resistance, outline the comparison of the new technology with the performances of traditional dies.

Deposition and Nanotribological Characterization of Sub-100-nm Thick Protective Ti-Based Coatings for Miniature Applications

Ti-based protective thin films with thicknesses below 100 nm, intended for miniature applications were deposited using physical vapor deposition magnetron sputtering. X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy were employed for the assessment of microstructure, morphology, film thickness, surface topography, and roughness. XRD pattern showed the formation of f.c.c TiN, TiCN, and TiC phases with different preferred orientations for films prepared in Ar/N2, Ar/N2 + C2H2, and Ar/C2H2 gas mixtures, respectively. Nanotribological performance was investigated using multipass nanoscratch technique at variable applied normal loads (100–400 μN). The nanoscale coefficient of friction was found to be in the 0.08–0.1 range, a sufficiently low value showing the potential of these films for miniature applications, such as microelectromechanical systems. The nanowear resistance at mean contact pressures in the range of 5–8.5 GPa for each sample was evaluated in terms of the average residual wear depth and an abrasive-dominated wear mechanism was found.

Precipitation Hardening Behaviour of Al-2Sc Micro Sheets

The continuous miniaturisation of products needed e.g. in the automotive or the micro electronic sector requires process chains which allow the manufacturing of microscopically small components in high quantities. The development of the required processes and technologies is the aim of the Collaborative Research Centre 747 “Micro Cold Forming” of the German Research Foundation. A necessary step in the manufacturing process chain is the heat treatment, which enables the adjustment of the semi-finished micro components to cold forming. Finally the usage properties have to be adjusted e.g. by precipitation hardening of aluminium alloys in order to increase the strength above the strain hardened level. To achieve a high strength aluminium alloy with elevated temperature stability in form of thin foils a new Al-Sc alloy with 2 mass-% scandium had to be developed within the Collaborative Research Centre. In comparison to conventional casting techniques it was possible to suppress Al3Sc precipitation and to ensure the supersaturated solid solution by using a Physical Vapour Deposition (PVD) Magnetron Sputtering process and low sputtering temperatures. Samples of the material are then artificially aged and characterised by ultra micro hardness measurements to evaluate the optimal ageing parameters. Besides this the microstructure was determined by light microscopy and Transmission Electron Microscopical (TEM) analysis.

Nanostructured self-lubricating CrN-Ag films deposited by PVD arc discharge and magnetron sputtering

CrN-Ag nanostructured coatings are deposited onto low-alloy steel substrates by means of Physical Vapour Deposition (PVD) reactive magnetron sputtering and PVD reactive arc discharge evaporation. The two different kinds of film have been characterized morphologically, chemically and tribologically. Depending on the used technique, as-deposited film shows different morphology, but in both cases, Ag nano-clusters are present on the surface. The annealing leads to coarsening of superficial Ag clusters and segregation out of the CrN matrix, depending on the temperature. After 600 °C annealing the surface is covered by an almost continuous layer of Ag, no matter which deposition technique is used. Tribological tests at different temperatures show that the lowest coefficient of friction appears at 600 °C for both coatings. The analysis of the wear tracks reveals that such a low friction is related to continuous Ag segregation out-of-CrN matrix, which enables self-lubrication.

Single-crystalline AlN growth on sapphire using physical vapor deposition

A novel technique for growing single crystalline aluminum nitride (AlN) films is presented. The novelty of the technique, specifically, comes from the use of an innovative physical vapor deposition magnetron sputtering tool, which embeds magnets into the target material. A relatively high deposition rates is achieved (∼0.2 μm/min), at temperatures between 860 and 940 °C. The AlN, grown onto sapphire, is single-crystalline as evidenced by observation using transmission electron microscopy. Tool configuration and growth conditions are discussed, as well as a first set of other analytical results, namely, x-ray diffraction and ultraviolet-visible transmission spectrophotometry.

DC-MSIP/HPPMS (Cr,Al,V)N and (Cr,Al,W)N thin films for high-temperature friction reduction

The application of high-strength steel and aluminum alloys entails increasing demands on the surfaces of tools used for forming processes. A promising approach towards the reduction of friction forces and thus towards the wear of tools is the application of self-lubricating coatings. Due to the high number of crystallographic shear planes and a partially low melting temperature, the so-called Magnéli-phases offer excellent possibilities for the reduction of friction in tools at application temperatures between 600 °C and 800 °C. In order to achieve the aforementioned gliding planes vanadium (V) and tungsten (W) containing (Cr,Al)N thin films deposited via a combination of Magnetron Sputter Ion Plating (MSIP) and High Power Pulse Magnetron Sputtering (HPPMS) Physical Vapor Deposition (PVD) were activated in a high-temperature environment. In this context, the (Cr,Al)N matrix provides for wear protection while vanadium and tungsten are developing friction-reducing oxides under temperature influence. Hence, a diffusion of these metals to the surface during application is necessary for a continuous generation of dry or liquid lubricants. Within this paper a scanning electron microscope (SEM) was used for the analysis of the cross-section fractures of the coatings in order to allow statements about the coatings' morphology and thickness; further, annealing tests in an atmosphere furnace at 600 °C, 800 °C and 1000 °C were carried out. X-ray diffractometry (XRD) served for documentation of phase transformations. With an electron probe micro analysis (EPMA) the diffusion of elements was observed. To investigate the friction reduction high-temperature pin-on-disk (PoD) tribometer measurements (room temperature (RT), 600 °C and 800 °C) using a 100Cr6 counterpart were, moreover, carried out in atmosphere. Within these investigations we could show a reduction in the friction coefficient from 0.6 at room temperature to 0.05 at 800 °C for the (Cr,Al,V)N coating. Furthermore, a diffusion of V to the surface of the coating was demonstrated. However, a positive effect by using (Cr,Al,W)N cannot be verified.

Nanomechanical and Electrochemical Properties of Diamond-Like Carbon (DLC) Films Deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) Technique

Diamond-like carbon (DLC) films was deposited successfully on stainless steel substrates with Si/SiC intermediate layers by combining plasma enhanced unbalanced magnetron sputtering physical vapor deposition (PEUMS-PVD) and microwave electron cyclotron resonance plasma enhanced chemical vapor deposition (MW-ECR PECVD) techniques. The effect of silicon dopant on the structure, morphology, nanomechanical properties and electrochemical behavior of DLC films were investigated by Raman spectroscopy, nano-indentation, atomic force microscopy (AFM) and potentiodynamic method and electrochemical impedance spectroscopy (EIS). It showed that the incorporated silicon atoms substituted sp2-bonded carbon atoms in the ring structures, promoting the formation of sp3-bonds. The structural transition from C-C to C-Si bonds resulted in the relaxation of the residual stress, leading to the decrease in films hardness. The DLC films with Si/SiC intermediate layers led to significant improvement in the corrosion resistance of the stainless steel substrate due to effective isolation and good chemical inertness of the DLC films.