Field Unbalanced Magnetron Sputtering Research Articles

Characterisation of mechanical and wear properties of NiAl and Ni-Al-N thin films deposited by closed field unbalanced magnetron sputter ion plating

NiAl and Ni-Al-N thin films with a thickness of approximately 1 μm have been deposited onto glass and stainless steel 316 substrates using closed field unbalanced magnetron sputter ion platting process. A CSM scratch tester was used to determine the critical load, the coefficient of friction and wear rate of the films. XRD analysis confirmed the presence of β-NiAl phase. EDAX revealed nearly equal atomic composition of Ni and Al at 300 W for Ni and 400 W for Al targets, respectively with the Ni-Al-N thin films showing a nickel rich NiAl phase. AFM indicated a smooth surface finish with surface roughness ≤ 100 nm. Nanoindentation for coatings on glass substrates displayed hardness and elastic modulus of 7.7 GPa and 100 GPa respectively. Hardest coatings obtained were at 10% of N content. Scratch test of coated samples gave critical load, friction of coefficient and wear rate of 24 N, 0.24 and 1×10−6 mm3/m respectively on steel.

Synthesis and Characterization of CrXN Nano-Multilayer Coatings

Three types of nano-multilayer coatings, CrSiN, CrAlN and CrMoN, with different Si, Al and Mo contents were deposited on M42 substrates using a closed field unbalanced magnetron sputter ion plating (CFUMSIP) technique. Systematic characterization on the chemical composition, microstructure, hardness and wear properties of these multilayer coatings has been investigated using GDOES, low angle XRD, SEM, TEM, nanoindentation and wear tests. Experimental results revealed that all these three types of Cr, XN ternary coatings (X=Al, Si and Mo) are nano-multilayer structured. The CrAlN multilayer coatings showed the highest hardness and oxidation resistance among these three multilayer coatings. The CrMoN multilayer coatings exhibited the lowest friction coefficient although no appreciable improvements in wear resistance were observed as compared with the optimized CrN coatings.

Microstructure and Properties of Low Temperature Deposit Cr<sub>x</sub>N Using Unbalanced Magnetron Sputtering

CrxN coatings are deposited on the substrates with low temperature using a Teer UDP 550 Close Field Unbalanced Magnetron Sputter Ion Plating system (CFUBMSIP). The effect of applied power on Cr targets related to sample temperature is studied. When the applied power of Cr targets is lower than 1.1KW, the depositing temperature could be controlled at about 180°C. Scratch test shows no coating detachment at the end of scratch track up to 85N load. All results of Rockwell-C indentation indicate that CrxN coating holds good bonding strength. Pin-on-disc tests are performed to evaluate wear resistance of the coatings and no any wear loss can be detected after 6000s and 1800s of running. XRD profile demonstrates that the coating deposited in this study is CrxN.

Microabrasive Wear Resistance of CrN and CrSiN Coatings

Evaluation of the wear resistance for tools and dies, particularly for coated components, is a challenging task in surface engineering testing. Pin-on-disc is a widely employed method in the literature; its result is rather associated with the friction aspect of the samples than wear resistance for components. A microabrasive test has been suggested recently to assess the wear resistance of hard coatings. The key point in that is to simulate the aspect which is close to the factor of the industrial performance for most of the components. This paper aims to compare pin-on-disc tests and microabrasive methods. Two hard coatings of CrN and CrSiN were deposited using a closed field unbalanced magnetron sputter ion plating system. SiC was used as the abrasive particle in the slurry. Results show that the abrasive wear rates of the CrN coatings changed sensitively with the depositing parameters. At the same time, the specific wear rate from pin-on-disc test was not able to pick up the change of wear endurance of the coatings. A hole drilling test indicates that the number of holes increases significantly when the abrasive wear rate is lower than a certain critical value. It is concluded that the microabrasive test is an appreciable method in practice to evaluate the wear resistance of hard coatings.

Substrate Bias Effects on Mechanical and Tribological Properties of Nanoscale Multilayer CrTiAlN Coatings Prepared by Closed Field Unbalanced Magnetron Sputtering Ion Plating Method

Substrate Bias Effects on Mechanical and Tribological Properties of Nanoscale Multilayer CrTiAlN Coatings Prepared by Closed Field Unbalanced Magnetron Sputtering Ion Plating Method

Surface free energy of non-stick coatings deposited using closed field unbalanced magnetron sputter ion plating

Semiconductor IC packaging molding dies require wear resistance, corrosion resistance and non-sticking (with a low surface free energy). The molding releasing capability and performance are directly associated with the surface free energy between the coating and product material. The serious sticking problem reduces productivity and reliability. Depositing TiN, TiMoS, ZrN, CrC, CrN, NiCr, NiCrN, CrTiAlN and CrNiTiAlN coatings using closed field unbalanced magnetron sputter ion plating, and characterizing their surface free energy are the main object in developing a non-stick coating system for semiconductor IC molding tools. The contact angle of water, diiodomethane and ethylene glycol on the coated surfaces were measured at temperature in 20 °C using a Dataphysics OCA-20 contact angle analyzer. The surface free energy of the coatings and their components (dispersion and polar) were calculated using the Owens–Wendt geometric mean approach. The surface roughness was investigated by atomic force microscopy (AFM). The adhesion force of these coatings was measured using direct tensile pull-off test apparatus. The experimental results showed that NiCrN, CrN and NiCrTiAlN coatings outperformed TiN, ZrN, NiCr, CiTiAlN, CrC and TiMoS coatings in terms of non-sticking, and thus have the potential as working layers for injection molding industrial equipment, especially in semiconductor IC packaging molding applications.

Surface Free Energy of Alloy Nitride Coatings Deposited Using Closed Field Unbalanced Magnetron Sputter Ion Plating

The sticking of product material to injection molding tools is a serious problem, which reduces productivity and reliability. Depositing alloy nitride coatings (TiN, ZrN, CrN, and TiAlCrN) using closed field unbalanced magnetron sputter ion plating and electrodeposition of chromium, and characterizing their surface free energies in the temperature range 20–120 � C have led to the development of a non-sticking (with a low surface free energy) coating system for semiconductor IC packaging molding dies. The contact angles of water, diiodomethane and ethylene glycol on the coated surfaces were measured at temperatures in the range 20–120 � C using a Dataphysics OCA-20 contact angle analyzer. The surface free energy of the coatings and their components (dispersion and polar) were calculated using the Owens-Wendt geometric mean approach. The surface roughness of these coatings were investigated by atomic force microscopy (AFM). The adhesion force of these coatings were measured using direct tensile pull-off test apparatus. The experimental results revealed that TiAlCrN, CrN and ZrN coatings outperformed Hard-Cr and TiN coatings in terms of anti-adhesion, and thus have the potential as working layers for injection molding industrial equipment, especially in semiconductor IC packaging molding applications. [doi:10.2320/matertrans.47.2533]

Effect of crystallographic orientation on the friction and wear properties of Mo xS y–Ti coatings by pulsed-dc in nitrogen and humid air

This work reports on the structural and wear properties of Mo x S y –Ti films, deposited on D2, 52100, and 440C steel substrates by pulsed-dc magnetron sputtering. A closed field unbalanced magnetron sputter ion plating system was used for the deposition process. The mechanical and tribological properties of Mo x S y –Ti coated composites onto selected steel substrates were characterized using microhardness test, friction–wear test in atmospheric conditions and in dry nitrogen. The X-ray diffraction (XRD) was used to determine the phase structure. Structural analysis was performed using SEM-EDS. Mo x S y –Ti films showed a very dense structure with pronounced basal plane (0 0 2) orientation, which showed the lowest friction coefficient (0.022) in dry nitrogen. The coefficient of friction can be attributed to the oxidation of MoS 2 at the wear track to form MoO x that is known to cause an increase in the friction coefficient. In humid air, an oxidative environment, the films had higher coefficient of friction (0.07), and lower wear life (142 500 passes with 2.11 × 10 −6 mm 3/N m wear rate) than in dry nitrogen, where the wear life was over 250 000 passes with the lowest wear rate of 3 × 10 −8 mm 3/N m.

An investigation of an industrial coating environment with planar probe technology

A novel electrostatic probe method has been applied to the plasma characterization of an industrial magnetron-based ion plating plasma system. The probe consists of a small, 7-mm diameter, disk fitted with a guard ring and mounted near the substrate position. A negative DC self-bias is achieved on the probe surface relative to the plasma by application of a radio frequency (RF) burst across an in-line capacitor. Following the termination of the RF burst a current–voltage characteristic is obtained as the probe potential returns to a floating condition through the arrival of positive ions from the plasma. Use of capacitively coupled RF biasing permits operation of the probe in a deposition environment. The guard ring maintains sheath planarity at the probe surface and eliminates edge effects. Total positive ion flux and the energetic tail of the electron distribution function are determined from the probe's current–voltage characteristic. Results are reported for ion flux and electron energy distribution measurements in DC and pulsed DC plasmas in closed field unbalanced magnetron sputter ion plating (CFUBMSIP) industrial coating equipment. Argon and combined argon and reactive gas atmospheres at below 0.5 Pa were used. Measurements are correlated with the deposition system's configuration and deposition parameters, including magnetron and substrate voltages, bias currents, and pulsing conditions. Potential applications and limitations of the planar probe technique for routine process control in an industrial coating environment are discussed.

Development of duplex nitrided and closed field unbalanced magnetron sputter ion plated CrTiAlN-based coatings for H13 aluminium extrusion dies

Extruded aluminium alloy is already a ubiquitous engineering material, but there is increasing demand for aluminium-based metal matrix composites (MMCs) with improved stiffness and wear resistance to further extend the material's range of application. The extrusion of MMCs containing significant quantities of hard, second-phase particulates places particular demands on the die, which must obviously maintain its critical mechanical and tribological characteristics, while resisting chemical and abrasive wear during exposure to the flowing aluminium MMC under conditions of high temperature and pressure. Many advanced applications demand the fine control of both the dimensional tolerance and surface finish of the extrudate, while maximising the productive lifetime of the associated die and minimising scrap, setup costs, etc. The development of an advanced duplex treatment for H13 steel extrusion dies, combining gas nitriding and closed field unbalanced magnetron sputter ion plating (CFUBMSIP) of high-performance CrTiAlN-based coatings, is described. Both the intended application and the detailed laboratory testing of coated substrates, using the pin-on-disc and abrasive wear testing are reported.

Industrial Application of Pulsed Dc Bias Power Supplies in Closed Field Unbalanced Magnetron Sputter Ion Plating

Pulsed dc power supplies are now commonly used in the reactive magnetron deposition of dielectric coatings from conductive or partially conductive sputtering targets. Their advantages, particularly the elimination of arcing and enhanced process stability are well recognised. In comparison, the application of pulsed dc power to the biasing of substrates in ion plating processes has received much less attention. The present study draws on experience with a range of pulsed dc bias supplies in industrial coating equipment, exploiting closed field unbalanced magnetron sputtering technology. Pulsed plasma characteristics have an impact on all stages of the coating process, from initial surface cleaning through to interface formation and the coating of components, requiring the appropriate selection of pulsing parameters. The synergistic interaction of pulsed dc bias, dc and pulsed dc closed field magnetron sources is explored. Practical considerations, such as the processing of thermally sensitive materials and the preservation of critical surface characteristics, are also discussed. SE/517

Dry Sliding Wear of TiNx PVD Coating on 7075-T6 Aluminium Alloy

The present paper studies the dry sliding wear behaviour of a 7075-T6 aluminium alloy coated with a substoichiometric TiNx film. The coating was deposited industrially (Teer Coatings Ltd) using the closed field unbalanced magnetron sputtering ion plating (CFUBMSIP) deposition technique. Coating characteristics such as morphology, thickness, compositional variation with thickness, residual stress, composite hardness and absolute hardness are also presented. The wear tests were conducted in a ball on disc tribometer, where a constant sliding velocity of 0.1 m s–1 and normal loads of 1, 2 and 5 N were used. The static counterparts employed during the test were 6 mm diameter balls made of AISI type 52100 steel. For comparison, the wear behaviour of the uncoated alloy is also reported. Both the maximum Herztian pressure and the von Mises stress values in the TiN coated aluminium alloy for each normal load used during the wear test were calculated, employing a commercially available software package Elastica 2.0.5, and the results were related to the wear performance. It was shown that the coated alloy presented an improved wear resistance only when the wear tests were performed at normal loads as low as 1 and 2 N, when the material from the static counterpart was transferred to the surface of the coated discs, and the TiN coating was able to protect the aluminium alloy from plastic deformation. However, when the wear test was carried out at a load of 5 N, the coating presented low wear resistance with a wear coefficient as low as 10–4 mm3 (N m)–1. This behaviour could be attributed to the fact that, in these conditions, the coating could not protect the substrate from plastic flow and fracture, producing a large amount of debris, which contributed to the abrasive wear of the system. SE/S277

The industrial application of pulsed DC bias power supplies in closed field unbalanced magnetron sputter ion plating

The advantages of using pulsed DC power supplies in the reactive magnetron deposition of dielectric coatings from conductive or partially conductive sputtering targets are well recognised, particularly in terms of the elimination of arcing and enhanced process stability. Less attention has been paid, however, to the application of pulsed DC power to the biasing of substrates in ion plating processes. This paper draws on our seven years of practical experience of using a range of pulsed DC bias supplies in a wide variety of industrial coating equipment exploiting closed field unbalanced magnetron sputtering technology. The selection of pulsed plasma characteristics for surface cleaning, interface formation and the coating of components is investigated, including parameters such as voltage, frequency, pulse width and pressure. The effectiveness of such pre-cleaning is evaluated, for example, by the subsequent scratch adhesion testing of the coatings. The synergistic interaction of the bias with DC and pulsed DC closed field magnetron sources is explored. The additional process flexibility provided by the pulsed bias technique can facilitate the processing of thermally sensitive materials and the preservation of critical surface characteristics.

The effect of surface chemistry and nanotopography of titanium nitride (TiN) films on 3T3-L1 fibroblasts.

The cell-material interaction of 3T3-L1 fibroblasts with TiN films was studied in vitro. TiN films were deposited onto glass substrates to thicknesses of 0.2 and 1.0 microm by pulsed dc reactive magnetron sputtering. For comparison TiN films were deposited by closed field unbalanced magnetron sputter ion plating by Teer Coatings Ltd. (Hartlebury, UK) to result in TiN films with similar surface chemistries but having increased topographical features. TiN films were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy. The cell-material interaction was examined morphologically by monitoring fibroblast attachment and growth and comparing to a control substrate. At early time points increased numbers of 3T3-L1 fibroblasts were found to preferentially attach to TiN films with an increase in the percentage of surface interstitial nitrogen and also with decreased topographical features. At later time points the presence of nanotopography appeared to play a greater role than the effects of surface chemistry and resulted in increased numbers of attached 3T3-L1 fibroblasts. The results show that by changing the deposition route and parameters to produce TiN films, the resultant films can be used to investigate the cellular response to surfaces of differing chemistry and topography.

The effect of surface chemistry and nanotopography of titanium nitride (TiN) films on primary hippocampal neurones

The cell–substrate interaction of primary hippocampal neurones with thin films of TiN was studied in vitro. TiN films of different surface chemistries and topographies were deposited by pulsed DC reactive magnetron sputtering and closed field unbalanced magnetron sputter ion plating by Teer Coatings Ltd., Hartlebury, UK to result in TiN films with similar surface chemistries but different topographical features. TiN films were characterised using X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy. The neuron–substrate interaction was examined using environmental scanning electron microscopy (FEG-ESEM) for morphological information. Bromodeoxyuridine and TUNEL assays were used to identify proliferating neurones as well as apoptotic neurones. Fluorescent staining for MAP-2 was used to label neuronal network formation. Primary hippocampal neurones were found to attach and spread to all of the TiN film chemistries and topographies investigated. Neuronal network morphology appeared to be more preferential on the nitrogen rich TiN films and also with reduced nanotopographical features.

Tribological performance of amorphous carbon films prepared on steel substrates with carbon implantation pre-treatment

The paper discusses the tribological performance of amorphous carbon films deposited on steel substrates with the pre-treatment of carbon ion implantation. Prior to deposition, the steel substrates were implanted with a metal vapour vacuum arc (MEVVA) ion source in order to create a carbon composition gradient layer on the surface. Subsequently, non-hydrogenated amorphous carbon films were prepared by a closed field unbalanced magnetron sputtering ion plating (CFUBMSIP) technique. The tribological tests using a conventional ball-on-disk tribometry showed that the films exhibited excellent performance during dry sliding. Low friction coefficients (<0.1) and almost zero wear rates were observed at a normal load of 70 N over 30,000 rotation cycles of unlubricated sliding against WC balls. In multi-pass reciprocating wear test under severe conditions (90 N load), the films on the implanted substrates could endure 16,000 passes; whereas the films with CCr x or Cr interlayers failed at the very beginning of the sliding.

The effect of relative humidity on wear of a diamond-like carbon coating

Sliding wear behaviour of a diamond-like carbon (DLC) coating deposited using the combined closed field unbalanced magnetron sputter ion plating and plasma assisted chemical vapour deposition technique has been investigated against tungsten carbide balls in air with various relative humidity (RH) levels as well as in water. A smooth transfer layer was always formed on the ball surface and wear of the ball was negligible. The wear rate of the coating decreased significantly with increase in RH, with sliding in water showing the lowest wear rate. When sliding in dry air or in a vacuum, the coating failed very quickly, producing a wear rate of approximately two orders that for sliding in humid air. Under the investigated conditions, sliding speed (0.25 and 0.05 m s −1) had no significant effect on the wear behaviour of the DLC coating in the various environments. The role of humid air in reducing wear rate of the DLC coating has been attributed to the formation of low energy surfaces by the adsorption of water at the dangling carbon bonds on the edge-faces of the sp 2 clusters in the DLC coating.

Multilayer nitride coatings by closed field unbalanced magnetron sputter ion plating

A range of ceramic multilayer nitride coatings, including Nb x Ti y N, Nb x Zr y N, and Mo x Zr y N, has been successfully deposited onto tool and die steels by closed field unbalanced magnetron sputter ion plating. The mechanical properties of the resulting coatings, including adhesion and hardness, have been evaluated by micro- and nano-indentation techniques, scratch testing etc. H Plast hardness up to 53 GPa has been achieved in the case of the Nb x Ti y N multilayers, 43 GPa for Nb x Zr y N and 38 GPa for Mo x Zr y N. The detailed microstructure of the coatings, including their respective nm-scale multilayer repeat distance, Λ, has been studied by advanced analytical techniques including high resolution transmission electron microscopy, ion backscattering (Rutherford, and non-Rutherford), and glancing angle X-ray diffraction, and focused ion beam machining and imaging. The coating properties are reviewed and correlated with the analytical data. Potential applications for, and some limitations of, the selected coatings are discussed.

Multi-pass sub-critical load testing of titanium nitride coatings

TiN coatings deposited by closed field unbalanced magnetron sputter ion plating (CFUBMS) have been scratch tested in two modes. An initial conventional scratch test has been carried out to determine the critical load, and multiple scratches have been made over single tracks at different fractions of the critical load. It is shown that, even at very high fractions of the critical load, the coatings do not fail adhesively or cohesively; rather, they simply become progressively thinner with successive passes of the diamond. Scanning electron microscopy of the worn surfaces has revealed a previously unobserved wear mechanism that shows that the coating adhesion can be truly described as perfect.

Properties of sputter-deposited MoS 2/metal composite coatings deposited by closed field unbalanced magnetron sputter ion plating

It has been proved that the co-deposition of a proper amount of titanium can significantly improve the properties of sputter-deposited MoS 2 coatings, leading to the deposition of coatings, which are harder, much more wear resistant and also less sensitive to atmospheric water vapour during tribological testing. The MoS 2/Ti coatings, studied here by the authors, also give excellent industrial results in a wide range of applications. In this paper the mechanical and micro-structural properties of MoS 2 coatings containing titanium with molar fractions up to 0.44 are studied. The mechanical properties are tested with pin-on-disk and reciprocating wear tests (multipass) in different experimental conditions. Frictional force and friction coefficient against a number of cycles are recorded. Coatings composition is determined by Rutherford and non-Rutherford backscattering (RBS) and coating thickness is measured by cross-section scanning electron microscopy (SEM). Structural analysis is carried out using X-ray diffraction (XRD). The mechanical properties are presented as a function of the Ti content and the optimal titanium concentration is determined. Other metals like Cr, W, Zr and Mo are also investigated. The composition of MoS 2/metal composite coatings of the same quality of the MoS 2/Ti films (‘optimized’ coatings) is studied by RBS.