Physical Vapor Deposition Coatings Research Articles

Silicon etch with chromium ions generated by a filtered or non-filtered cathodic arc discharge

The pre-treatment of substrate surfaces prior to deposition is important for the adhesion of physical vapour deposition coatings. This work investigates Si surfaces after the bombardment by energetic Cr ions which are created in cathodic arc discharges. The effect of the pre-treatment is analysed by X-ray diffraction, Rutherford backscattering spectroscopy, scanning electron microscopy and in-depth X-ray photoemission spectroscopy and compared for Cr vapour produced from a filtered and non-filtered cathodic arc discharge. Cr coverage as a function of ion energy was also predicted by TRIDYN Monte Carlo calculations. Discrepancies between measured and simulated values in the transition regime between layer growth and surface removal can be explained by the chemical reactions between Cr ions and the Si substrate or between the substrate surface and the residual gases. Simulations help to find optimum and more stable parameters for specific film and substrate combinations faster than trial-and-error procedure.

Coloration of metallic and/or ceramic surfaces obtained by atomic layer deposited nano-coatings

By depositing single layer coatings by means of physical vapor techniques, tailoring of their coloration is generally complex because a given color can be obtained only by very high composition control. Physical vapor deposition (PVD) processes are expensive and cannot be easily used for obtaining conformal coating on three-dimensional objects. Moreover PVD coatings exhibit intrinsic defects (columnar structures, pores) that affect their functional properties and applications such as barrier layers.Atomic layer deposition (ALD) technology delivers conformal coatings on different materials with very low defectiveness. A straightforward coloration can be obtained by a combination of two types of layers with different refraction index, deposited to high thickness precision.Computer simulation studies were performed to design the thickness and architecture of multilayer structures, to a total thickness of approximately 100nm, suitable to modify the typical coloration of some materials, without altering their other physical and chemical properties.The most promising nano-layered structures were then deposited by ALD and tested with regard to their optical properties. Their total thicknesses were specified in such a way to be technically feasible and compatible with future industrial production.The materials employed in this study to build the optical coatings, are two oxides (Al2O3, TiO2) deposited at 120°C and two nitrides (AlN, TiN), which need a deposition temperature of 400°C.The possibility of using such modern deposition technology for esthetic and decorative purposes, while maintaining the functional properties, opens perspectives of industrial applications.

Comparison of TiN-coated tools using CVD and PVD processes during continuous cutting of Ni-based superalloys

Abstract High-strength, low-conducting Ni-based superalloys require higher cutting force and cutting temperature than other materials during the machining process. To understand how the coating characteristics such as defects formation and physical and mechanical properties affect cutting performance, TiN coatings were deposited by three physical vapor deposition (PVD) methods (arc ion plating, sputtering, and hollow cathode) and chemical vapor deposition (CVD). Sputtering and CVD yielded TiN coatings with fewer defects than other methods. Subsequently, the damage to the TiN coatings during machining of alloy 718 was investigated under continuous turning. Tools coated by sputtering and CVD exhibited micro-abrasion wear without heavy fracture or delimitation of the coating. Furthermore, the CVD coating showed the best cutting performance and lower plastic deformation than the PVD coatings. TiN coatings were characterized by X-ray diffraction, nanoindentation, electron back-scatter diffraction, and transmission electron microscopy. As the hardness of the coatings was measured before and after heat treatment, the CVD coating was more resistant to softening due to heating than the PVD coatings. The reduced hardness of the PVD coatings was attributed to strain release, atomic rearrangement, and grain growth in the PVD coatings. Such high-strength coatings with good high-temperature stability and low-defect density offer strong protection to cutting tools during machining of Ni-based superalloys. Based on the results of this study, fine structure CVD-deposited coatings may be good candidate coating for cutting of the Ni-based superalloys.

Retrieval analysis of titanium nitride (TiN) coated prosthetic femoral heads articulating with polyethylene

Data regarding in vivo performance of titanium nitride (TiN) coated prosthetic femoral heads is scarce, and available studies of older generations of implants demonstrated coating wear in vivo. That is why we conducted a retrieval analysis of 11 femoral heads (articulating in vivo for 1–56 months) with TiN film formed using physical vapor deposition (PVD), to verify if coating failure is a problem in contemporary implants. Retrieved implants were examined using scanning electron microscope, coating roughness was evaluated with a contact profilometer and adhesion was tested using a Rockwell HRC test according to VDI 3824 guideline. Although no gross failure of the TiN coating was observed in our retrievals, all implants had defects typical for PVD coatings, such as pinholes, small titanium droplets and blisters with delaminated coating. In some heads the coating was contaminated with small niobium (Nb) droplets uniformly scattered on the entire surface of the film. Presence of Nb contamination was associated with an increased number and area of other types of defects and poorer coating adhesion. In one component, subjected to multiple dislocations we found severe delamination and cracking of the coating, increased roughness and the presence of third bodies. Our results indicate, that although wear of the coating is lower than seen in older generations of implants, inconsistent quality of the TiN film among different implants indicates the need for strict monitoring of the manufacturing process.

Damage of physical vapor deposition coatings of cutting tools during alloy 718 turning

Ni-based superalloys are typically difficult-to-cut materials. Therefore, the lifespan of cutting tools used to cut these materials is shorter than that of tools used on other materials. This study develops a new coating for cutting tools that has properties required for the turning of Ni-based superalloys. This study examined the cutting performance of TiN-coated cutting tools deposited by arc ion plating according to the damage of the coating and determination of the required properties of the coatings. To evaluate cutting tool damage, many analysis methods were used at each step of damage accumulation. Plastic deformation of the coating was observed at rake and flank face edges by scanning ion microscopy and transmission electron microscopy (TEM). Furthermore, the fracture of the coating near the surface defects (e.g., droplets, voids) was due to the interaction between the work material and surface defects. Moreover, using electron probe microanalysis, scanning auger microscopy, and TEM, the work material was confirmed to adhere to the cutting edge physically or mechanically, not chemically. This means that oxidation and diffusion did not occur in the interface between the adhesive material and coating after cutting. Finally, the effectiveness of different coating types, varying in both composition and deposition method, was verified by evaluating the effect of damage reduction. Using coatings with greater stability at high temperatures and fewer defects can reduce damage of the coated cutting tools, increasing tool lifespan.

Wear of different PVD coatings at industrial fine-blanking field tests

Thin hard physical vapor deposited (PVD) coatings play significant role on wear performance of fine-blanking punches in the presence of extremely high contact stresses. Nevertheless it seems that in blanking or fine-blanking the coatings are selected based on coincidence, trial-error-method or latest trends. There is limited information about planning and conducting the fine-blanking industrial field tests and measuring the wear of different coatings. In the present study a set of fine-blanking punches and laboratory specimens were prepared with three coatings – TiCN, nACRo and nACo. As substrate material Bohler S390 Microclean high speed steel was used. Coating mechanical properties (modulus of elasticity and nanohardness) were measured and wear rate with alumina ball was determined using the reciprocating sliding test. Wear of coatings was measured from punches after industrial use. All of the tested coatings showed high variance of wear. However coatings nACo and nACRo have better average wear resistance in fine-blanking compared with the well-known TiCN. Industrial field tests show correlation to the ratio elastic strain to failure H/E. DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7249

Improvement of Wear Performance of High Speed Steel Tool Using Physical Vapour Deposition Coating Process

Manufacturing industries are presently using many tool materials, such as high speed steel, carbide tool and diamond tools etc. The most widely and commonly used tool in the engineering industries is high speed steel (HSS). The HSS tools are the cheapest and reliable for medium and small scale industries. In this work, the HSS single point cutting tool is taken as substrate material and coated with two different combinations of TiAlN composite coating using Physical vapour deposition (PVD) technique. Also, Tool life was calculated and compared with uncoated HSS tool. The hardness and surface roughness value for both the tools have been taken under same condition. The loss of weight in the tool after machining has been weighed using standard equipments. The differences have been closely observed with sufficient trials and find out the loss in weight in both the tools. The weight loss percentage was calculated after proper machining trials. The tool life of the Titanium Aluminium Nitride (Ti 70%, Al 25%) coated tool has been increased by 3.74 times than that of uncoated tool. The surface finish for TiAlN (Ti 70%, Al 25%) coating is better than the uncoated tool. The PVD coated tools having better performance comparing with uncoated HSS tool.

Investigation on microstructures and mechanical properties of AlCrN coatings deposited on the surface of plasma nitrocarburized cool-work tool steels

AlCrN coating which has been widely applied in industrial application was produced on the surface of nitrocarburized SKD 11 cool-work tool steel by physical vapor deposition (PVD) method. The effects of nitrocarburizing pretreatment and PVD deposition temperature on microstructures, mechanical and tribological properties of the coatings were investigated. The results show that the AlCrN coating consists of an inner CrN adhesion layer with columnar growth and an outmost AlCrN work layer with planar growth, and the AlCrN coating shows a superior hardness of about 43 GPa. The nitrocarburizing pretreatment considerably improve adhesion strength, load capacity and wear resistance of duplex coated samples when compared with the single AlCrN coated samples. The improved mechanical and tribological properties are mainly related to the thicker nitrocarburizing layer and the gradient in the hardness profile of the duplex coating. In addition, the nitrocarburizing-PVD AlCrN duplex coated samples can be further enhanced by increasing deposition temperature of PVD coatings. The main wear mechanisms of duplex coated samples are oxidation wear or oxidation wear and adhesion wear, whereas the main wear mechanisms of single AlCrN coated samples are spalling and chipping wear as well as oxidation wear.

Investigation on plastic behavior of HPPMS CrN, AlN and CrN/AlN-multilayer coatings using finite element simulation and nanoindentation

Abstract A comprehensive investigation of hard coatings deposited by physical vapor deposition (PVD) requires, in addition to the elastic properties, a precise knowledge of their plastic behavior. Nanoindentation is a commonly applied method to determine the hardness and the elastic modulus of PVD coatings. Determination of flow curve of PVD thin coatings using a combination of nanoindentation and finite element (FE) simulation is the subject of current research. In the presented work, nanoindentation tests with a Berkovich tip, in combination with its FEM simulation, were used to determine the plastic flow curves of CrN, AlN and CrN/AlN-multilayer coatings deposited by high power pulse magnetron sputtering (HPPMS) PVD on cemented carbide substrates. The applied FEM model was used to simulate the indentation process. The details of the FEM model and the applied experimental and analytical methods are discussed. The determination of the simulative flow curves was carried out according to the Johnson–Cook model and by finding the coefficients of the considered plastic flow model. The coefficients were determined by comparing the simulated and measured maximum forces, and additionally, by correlating the indentation imprints after nanoindentation tests in simulation and experiment. The correlation was performed by depth profiling of the indentation imprints using confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). The plastic behavior of the studied coating systems was analyzed combining the simulated flow curves and the results of the analysis of indentation imprints. The results show a higher resistance of the nanostructured CrN/AlN-multilayer coating against plastic deformation compared to CrN and AlN. This is most likely due to the nm-sized alternating layers and the fine grained morphology of the CrN/AlN-multilayer compared to the pure coatings, which hinders the dislocation motion.

Friction reduction of highly-loaded rolling-sliding contacts by surface modifications under elasto-hydrodynamic lubrication

Due to the operation in mixed and boundary friction, minimization of friction losses in automobile powertrains offers high potential for lowering of greenhouse gas emissions and saving fossil fuels. In cooperation between Surface Engineering Institute (IOT) and Gear Research Center (FZG), surface modifications in terms of stochastic and deterministic structures, diamond-like carbon (DLC) and nitride hard physical vapor deposition (PVD) coatings were tested in lubricated rolling-sliding contacts in twin-disk and gear efficiency test-rig. It was found that deterministic structured surfaces provide for reduction of friction losses by up to 7% under extreme boundary friction conditions at high Hertzian stresses and small relative lubricant film thicknesses. Application-oriented tests using DLC coated gear wheels in gear efficiency test-rig exhibited a reduction of friction losses between 10% and 21% compared to uncoated gear wheels. The DLC coating ZrCg developed at IOT provided for friction reduction of 15% for small circumferential speeds in boundary friction. Friction losses were reduced by up to 39% at higher circumferential speeds in spite of fully separated surfaces in the fluid friction regime. Due to their thermophysical properties, it is assumed that DLC coatings have an impact on viscosity and shear resistance of the lubricant.

A dynamic FEM simulation of the nano-impact test on mono- or multi-layered PVD coatings considering their graded strength properties determined by experimental–analytical procedures

Nano-impact test is a reliable method for assessing the brittleness of PVD coatings with mono- or multi-layer structures. For the analytical description of this test, an axis-symmetrical Finite Element Method (FEM) model was developed using the LS-DYNA software. This software was adequate to simulate the progressive superficial coating fracture induced by the repetitive nano-impacts during the nano-impact test. The coating possesses one or more individual layers with own mechanical properties, since every layer after its deposition at the PVD process temperature is exposed to an annealing affecting its strength data. The annealing duration of each layer is associated with the rest time, up to the deposition of the overall coating thickness. For simulating this procedure and estimating the related mechanical properties of the coating layers, cemented carbide specimens with the same TiAlN PVD (Physical Vapor Deposition) coating of various thicknesses and structures were annealed in vacuum. The annealing duration was equal to the deposition time required for coating a specimen with a further layer up to a constant overall thickness. The superficial strength properties of these coatings were determined via nano-indentations, coupled with FEM calculations to estimate the corresponding stress–strain curves. Results obtained by the developed FEM model simulating the nano-impact test were compared with experimental ones. Taking into account the sufficient convergence between them, the introduced numerical procedure can be effectively employed to evaluate the effect of various coating structures on their brittleness.

Investigations Regarding Process Stability Aspects in Thread Tapping Al-Si Alloys

The large number of drills and taps in automotive powertrain components make these processes to a considerable machining step. Due to the fact that hypereutectic Al-Si alloys tend to adhere on the tool surface, the machinability of these alloys is challenging. Especially the adhesion of Al has a negative influence on the chip transportation and leads to an increase of stochastic inclinations of clogging the chip flute. A variety of physical vapour deposition (PVD) coatings like TiCN, CrN, TiB2 on carbide metal taps have been tested in machining experiments. Also two types of DLC coatings have been compared in the tests. In order to improve the chip transportation, the tribological effects were determined by investigating the affinity of build-up edge and aluminium adhesion in the rake flank. Results are discussed in terms of materials, which are fit for purpose of automotive powertrain machining steps.

Investigation of force parameters acting on a single cutting insert made of ceramics in face milling of hardened steel

In the present paper, mathematical models for force parameters affecting single cutting insert made of oxide ceramics during finish milling of hardened steels are derived taking into account wear of inserts. Experiments showed that nitride Physical Vapor Deposition (VPD) coatings on oxide ceramics substrate CC6(Al2 O3 -TiC) produced by Moscow State University of Technology “STANKIN” provide at least 10% decrease of cutting forces. It was realized that cutting inserts wear influences the force parameters, especially axial force P x , that makes it possible to use those parameters as diagnosis indicators.

A comparative study of surface deformation and quality of brass workpiece in contact with coated dies by pin-on-disc testing

Manufacturing technology must ensure the production of parts with required characteristics: dimensional accuracy, overall strength, and surface quality. The surface layers in metal forming generally remain at the surface. The quality of the deformed surface is therefore determined by the initial surface and the history of the various forming processes undergone. Surface roughness influences surface quality and wear of metal forming products. Pin-on-disc tests at a range of temperatures were employed to study the influence of die coatings on the surface quality of a two-phase brass alloy during forging operation. The pins were made in H13 hot work tool steel and given duplex surface treatments including plasma nitriding and physical vapor deposition (PVD) coatings. The discs were machined from CuZn38Pb2 forging brass. Mechanical properties, surface roughness, and compositional properties of pins were determined by nanoindentaion, two-dimensional profilometer, and scanning electron microscopy equipped with energy-dispersive X-ray detector, respectively. At 25 °C, wear track parameters were more affected by the changes in Young’s modulus and the surface roughness of the pins. At 250 °C, the highest tendency to adhesion was observed in H13 steel pin. At 700 °C, oxidation of the pins influenced the wear track parameters on the discs. R a parameters inside the wear tracks were constant at 25 and 250 °C, but R ku parameters were maximum for the wear tracks of disc in contact with plasma nitriding and H13 pins at 25 and 250 °C, respectively. At 700 °C, the lowest surface quality was for the disc in contact with H13 steel pin. It was concluded that in forging process of brass alloys, the surface quality and deformation behavior of workpiece were improved by applied PVD coating on the surface of the die.

Protection of yttria-stabilized zirconia for dental applications by oxidic PVD coating

In this study, the application of transparent physical vapor deposition (PVD) coatings on zirconia ceramics was examined as an approach to retard the low-temperature degradation of zirconia for dental applications. Transparent monolayers of titanium oxide (TixOy) and multilayers consisting of titanium oxide–alumina–titanium oxide (TixOy–AlxOy–TixOy) were deposited onto standardized discs of 3Y-TZP using magnetron sputtering. Using X-ray photospectroscopy and time-of-flight secondary-ion mass spectrometry, the compositions of the coatings were verified, and an approximate thickness of 50nm for each type of coating was ascertained. After aging the coated and uncoated samples in water vapor at 134°C and 3bar for 4, 8, 16, 32, 64 and 128h, the monoclinic phase content was determined using X-ray diffraction, and its impact on mechanical properties was assessed in biaxial flexural strength tests. In addition, the depth of the transformation zone was measured from scanning electron microscopy images of the fracture surfaces of hydrothermally aged samples. The results revealed that the tetragonal-to-monoclinic phase transformation of the zirconia ceramic was retarded by the application of PVD coatings. During the first stages of aging, the coated samples exhibited a significantly lower monoclinic phase content than the uncoated samples and, after 128h of aging, showed a transformation zone which was only ∼12–15μm thick compared to ∼30μm in the control group. Biaxial flexural strength decreased by ∼10% during aging and was not influenced by the application of a PVD coating.

Thermal Conductivity Analysis and Lifetime Testing of Suspension Plasma-Sprayed Thermal Barrier Coatings

Suspension plasma spraying (SPS) has become an interesting method for the production of thermal barrier coatings for gas turbine components. The development of the SPS process has led to structures with segmented vertical cracks or column-like structures that can imitate strain-tolerant air plasma spraying (APS) or electron beam physical vapor deposition (EB-PVD) coatings. Additionally, SPS coatings can have lower thermal conductivity than EB-PVD coatings, while also being easier to produce. The combination of similar or improved properties with a potential for lower production costs makes SPS of great interest to the gas turbine industry. This study compares a number of SPS thermal barrier coatings (TBCs) with vertical cracks or column-like structures with the reference of segmented APS coatings. The primary focus has been on lifetime testing of these new coating systems. Samples were tested in thermo-cyclic fatigue at temperatures of 1100 °C for 1 h cycles. Additional testing was performed to assess thermal shock performance and erosion resistance. Thermal conductivity was also assessed for samples in their as-sprayed state, and the microstructures were investigated using SEM.

Prolonging the Lifetime of PEEK Packages for Implantable Electronic Devices Using Commercially Available Vacuum Thin Film Coatings

For short term applications (less than three years), it may be possible to replace traditional long term packaging materials such as titanium with a biocompatible polymer such as PEEK. This paper investigates the use of commercially available thin films to decrease the water vapor permeation rate through the walls of a PEEK package. It was found that most physical vapor deposition (PVD) and plasma assisted chemical vapor deposition (PaCVD) coatings tested did not provide a significant improvement in lifetime, due to the porosity of the films produced. This is mostly linked to the morphology of the films (i.e., growth in columns which are poorly bonded together, creating a porous structure) and is exacerbated by the high surface roughness of the machined substrates. Applying a lacquer before coating reduces this effect significantly, and we found that the time constant of our coated packages was improved by a factor of 2.3. Based on the findings of our group's previous work and this paper, the maximum achievable lifetime of PEEK packages with a thin film coating and desiccant is presented. As an example, a coated cylindrical PEEK package (using atomic layer deposition, ALD) with a uniform wall thickness of 2 mm, an internal cavity size of 1.5 cm3, filled with 20% of desiccant, has a lifetime of 18.8 mo (27.2 mo with 30% of desiccant). This would be sufficient for a range of applications and provide a cheaper and more versatile packaging alternative to traditional packages.

Combined Surface Treatment of Electron Beam Alloying and PVD Hard Coating for Al Alloys

Due to their typically high hardness, excellent resistance against wear, and their low coefficient of friction, Physical Vapor Deposition (PVD) hard coatings are used on steels for a wide range of tools and components. Currently, however, the potential for wear protection of Al alloy components cannot be exploited. The thin PVD layers tend to collapse and disintegrate due to plastic deformation of the soft base material. Present research is focused on electron beam (EB) surface alloying, using Co-based additives to increase the surface hardness of the Al base material, producing an improved supporting effect for PVD coatings. The influence of different beam deflection techniques and EB parameters on the microstructure and hardness of alloyed layers was investigated. The properties of the duplex composite layers produced are strongly dependent on the thermal stability of the EB alloyed layers (type and amount of intermetallic compounds, coarsening effects) which are affected by the temperature-time cycle of the PVD process. This will be discussed by means of SEM and EDX investigations in correlation with XRD analysis. Measurements using scratch test with increasing load result in critical load values for the combined treatment that are 3 to 5 times higher when compared to only PVD-coated base material.

Microstructure, Interface, and Properties of Multilayered CrN/Cr2O3 Coatings Prepared by Arc Ion Plating

There has been much interest in developing multilayered or nanolayered physical vapor deposition (PVD) coatings identified as a group of promising protective coatings for their excellent mechanical properties and corrosion resistance. In this study, the multilayered CrN/Cr 2 O 3 coatings with different bilayer periods ( Λ ) were synthesized on the polished high speed steel substrates from a Cr target with the alternative atmosphere of pure nitrogen and pure oxygen by arc ion plating (AIP) technique. The results revealed that the microstructure, morphologies and properties of the multilayered coatings were strongly influenced by the bilayer period ( Λ ). There were two kinds of interfaces in the multilayered CrN/Cr 2 O 3 coatings: the sharp ones and the blurry ones. With reducing the value of Λ , the macro-particles densities decreased gradually, whereas the coating microhardness, adhesive strength and wear resistance first increased, and then decreased slightly or remained stable as the bilayer period Λ 2 O 3 coating with the bilayer period Λ of 590 nm possessed the best comprehensive properties, namely the highest microhardness, the strongest adhesion, and the lowest wear rate.

Effect of mechanical pre-treatments in the behaviour of nanostructured PVD-coated tools in turning

As a consequence of the lack of characterization of advanced physical vapour deposition (PVD) coatings in the scope of turning, a methodology is presented to evaluate the performance of nanostructured coated tools in the scope of difficult to machine materials turning in particular are austenitic stainless steels. A main aspect of this research is the evaluation of different mechanical pre-treatments before PVD coating in cutting tools. In a first stage, four advanced PVD coatings were analyzed prior to studying the effect of pre-treatments. This stage allowed to identify the nanostructured AlTiSiN coating, commercial denomination nACo, as the one with the best performance for turning austenitic stainless steel. Once the best coating is identified in a second stage, the influence of drag-grinding and microblasting mechanical substrate pre-treatments was analyzed with regard to the performance of coated tools. Several aspects were considered: geometric modification of cutting edge, coating adhesion, substrate roughness and machining performance. The performance of the mentioned coatings was evaluated through wear tests. The machined material was AISI 304L and machining operation was cylindrical turning. Each test started up using a new edge. Results showed that drag-grinding pre-treatment leads to improved coating adhesion and, therefore, in the performance of the tool. Therefore, combination of nACo coating with drag-grinding pre-treatment offers a good solution for difficult to machine metals.