Closed Field Unbalanced Magnetron Sputter Ion Plating Research Articles

Effect of Ni addition on the structure and properties of Cr–Ni–N coatings deposited by closed-field unbalanced magnetron sputtering ion plating

Closed-field unbalanced magnetron sputtering ion plating (CFUMSIP) is a versatile technique for the preparation of high-quality coatings due to the enhancement of plasma density during deposition. In this study, Cr–Ni–N hard coatings with different Ni contents (0–64at.%) were deposited onto AISI M2 steel substrates by CFUMSIP in Ar–N2 reactive gas mixtures. The coatings were characterized in terms of their structure and properties by a variety of techniques, such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), micro-indentation, reciprocating wear tester, etc. The surface free energy of the coatings was calculated using the Owens–Wendt geometric mean approach. The experimental results indicated that the microstructure and properties of Cr–Ni–N coatings changed with the incorporation of Ni content at different level. The resultant Cr–Ni–N coatings were consisted of Cr2N, CrN and metallic Ni mixed phases. With the appropriate addition of Ni in the range of 20–40at.%, the fracture toughness and wear resistance could be improved as compared to the Cr–N binary coating, and the hardness remained relatively high (20–23GPa). Additionally, both low total surface energy (18–22mN/m) and low polar component of surface energy (0.1–0.2mN/m) could be obtained in the Cr–Ni–N coating system. Therefore, the Ni incorporation can provide an effective route to tailor the structure and properties of the Cr–Ni–N coatings. The good combined properties of the Cr–Ni–N coatings demonstrate their potential for applications in plastic injection molding.

Development and characterization of multilayered Cr–C/a-C:Cr film on 316L stainless steel as bipolar plates for proton exchange membrane fuel cells

Multilayered chromium–carbon/amorphous carbon:chromium (Cr–C/a-C:Cr) is deposited on 316L stainless steel (SS316L) sheet as bipolar plates for proton exchange membrane fuel cells (PEMFCs) using closed field unbalanced magnetron sputter ion plating (CFUBMSIP). Raman spectra and X-ray diffractometry (XRD) indicate that the Cr–C/a-C:Cr film is composed of amorphous carbon, metallic Cr phase, chromium carbide phases. The stactic water contact angle of the film reaches 89.1°. Interfacial contact resistance (ICR) between the coated SS316L sheets and carbon paper is only 2.89 mΩ cm2 at 1.5 MPa. Potentiodynamic tests in the simulated corrosive circumstance of PEMFCs reveals that the corrosion potential of coated samples is 0.236V vs SCE and the passivation current density is 0.276 μA cm−2 at 0.6 V in simulated cathodic environment. A single cell with Cr–C/a-C:Cr coated SS316L bipolar plates is assembled and tested to evaluate the in-situ performance of the film. The peak power density of the single cell is 1278.2 mW cm−2 at a current density of 2674.1 mA cm−2. Compared to a-C coating developed in our previous work, the performance of Cr–C/a-C:Cr coating is improved in various aspects and Cr–C/a-C:Cr coated SS316L bipolar plates are more practically applied for commercialization of PEMFCs technology.

Cr–N–C multilayer film on 316L stainless steel as bipolar plates for proton exchange membrane fuel cells using closed field unbalanced magnetron sputter ion plating

To combine the advantages of chromium nitride (CrN) and amorphous carbon (a-C) film, this study proposes a novel Cr–N–C multilayer film on 316L stainless steel (SS316L) as bipolar plates for proton exchange membrane fuel cells (PEMFCs) using closed field unbalanced magnetron sputter ion plating (CFUBMSIP) method. The characterizations of Cr–N–C film are analyzed by X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), and scanning electron microscopy (SEM). Scratch tests indicate that the adhesion strength between the film and SS316L substrate has been greatly improved which is beneficial to prevent the multilayer film from spalling. Interfacial contact resistance (ICR) between coated SS316L sheets and simulated gas diffusion layer (GDL) decreases to 2.64 mΩ cm2 at 1.4 MPa. Potentiodynamic results reveal that the anodic corrosion potential of coated samples is more positive than the operation potential and the cathodic passivation current density is only 0.61 μA cm−2 at 0.6 V. Potentiostatic test, contamination analysis and surface morphology results reveal that the substrate is well protected by the Cr–N–C film. This research demonstrates that the novel Cr–N–C film exhibits excellent ex-situ performance including strong adhesion strength, high corrosion resistance and low ICR.

Development of PVD coatings for PEMFC metallic bipolar plates

Metallic PEM fuel cell bipolar plate (BPP) materials such as stainless steel typically suffer from insufficient corrosion resistance and/or interfacial contact resistance (ICR). Therefore, coatings with both high corrosion resistance and low ICR are required. Closed field unbalanced magnetron sputter ion plating (CFUBMSIP) was used to produce dense and well adhered TiN, TiN+C and Graphit-iC™ coatings on an AISI316L foil substrate. The ICR of the coatings was measured before and after a potentiostatic measurement at a cathodic standby PEMFC potential of 1V/SHE. Following the corrosion measurement only the TiN+C, Graphit-iC™ and 10nm Au coatings met the ICR and corrosion US DoE targets of <10mΩcm2 and <1μAcm−2. Potentiodynamic corrosion measurements of the applied coatings were carried out under the same conditions. The multilayer coating TiN+C showed improved corrosion resistance over single layer coatings of TiN and Graphit-iC™. Multilayer coatings and 10nm Au coatings were identified as the best candidates for future research.

Investigation of sintered stainless steel fiber felt as gas diffusion layer in proton exchange membrane fuel cells

The feasibility of using sintered stainless steel fiber felt (SSSFF) as gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs) is evaluated in this study. The SSSFF is coated with an amorphous carbon (a-C) film by closed field unbalanced magnetron sputter ion plating (CFUBMSIP) to enhance the corrosion resistance and reduce the contact resistance. The characteristics of treated SSSFF, including microscopic morphology, mechanical properties, electrical conductivity, electrochemical behavior and wettablity characterization, are systematically investigated and summarized according to the requirements of GDL in PEMFC. A membrane electrode assembly (MEA) with a-C coated SSSFF-15 GDL is fabricated and assembled with a-C coated stainless steel bipolar plates in a single cell. The initial peak power density of the single cell is 877.8 mW cm−2 at a current density of 2324.9 mA cm−2. Lifetime test of the single cell over 200 h indicates that the a-C coating protects the SSSFF-15 GDL from corrosion and decreases the performance degradation from 30.6% to 6.3%. The results show that the SSSFF GDL, enjoying higher compressive modulus and ductility, is a promising solution to improve fluid permeability of GDL under compression and PEMFC durability.

A study of TiMoN nano-multilayer coatings deposited by CFUBMSIP using DC and HIPIMS power

TiMoN nano-multilayer hard coatings have been deposited using the closed field unbalanced magnetron sputter ion plating (CFUBMSIP) technique. In one set of experiments, standard DC power supplies were used on four magnetrons in the CFUBMSIP system (4DC magnetrons). The second set of experiments was also in the same magnetic field configuration of CFUBMSIP, but three magnetrons were as again powered with standard DC whilst one magnetron with Ti target was supplied by a high power impulse magnetron sputtering (HIPIMS) power generator (3DC+1HIPIMS magnetrons). Two elemental titanium sputtering targets and two of molybdenum were used to produce the TiMoN nano-multilayer coatings. Analysis of the coatings was carried out to investigate the differences in terms of properties, compositions and microstructures of the coatings deposited by these two sets of experiments. It was found that the coatings deposited by both sets of the experiments exhibited similar properties of high hardness, good adhesion and exceptional wear resistance, with a lower sliding friction than more commonly used hard coatings including TiN, CrN, TiAlN, CrTiAlN etc. Although the initial TiN coating as formed at the coating-substrate interface using the process of 3DC+1HIPIMS magnetrons appeared to show a less oriented microstructure in comparison with that of the coating produced by the process using 4DC magnetrons, the compositions and cross sectional microstructures of the bulk of the coatings did not show significant differences, as observed by the cross sectional Transmission Electron Microscopy microstructures of these two types of TiMoN coatings.

Performance of a proton exchange membrane fuel cell stack using conductive amorphous carbon-coated 304 stainless steel bipolar plates

In this study, 304 stainless steel (SS) bipolar plates are fabricated by flexible forming process and an amorphous carbon (a-C) film is coated by closed field unbalanced magnetron sputter ion plating (CFUBMSIP). The interfacial contact resistance (ICR), in-plane conductivity and surface energy of the a-C coated 304SS samples are investigated. The initial performance of the single cell with a-C coated bipolar plates is 923.9 mW cm −2 at a cell voltage of 0.6 V, and the peak power density is 1150.6 mW cm −2 at a current density of 2573.2 mA cm −2. Performance comparison experiments between a-C coated and bare 304SS bipolar plates show that the single cell performance is greatly improved by the a-C coating. Lifetime test of the single cell over 200 h and contamination analysis of the tested membrane electrode assemble (MEA) indicate that the a-C coating has excellent chemical stability. A 100 W-class proton exchange membrane fuel cell (PEMFC) short stack with a-C coated bipolar plates is assembled and shows exciting initial performance. The stack also exhibits uniform voltage distribution, good short-term lifetime performance, and high volumetric power density and specific power. Therefore, a-C coated 304SS bipolar plates may be practically applied for commercialization of PEMFC technology.

Growth and Characterisation of NiAl and N-Doped NiAl Films Deposited by Closed Field Unbalanced Magnetron Sputtering Ion Plating Using Elemental Ni and Al Targets

Closed Field Unbalanced Magnetron Sputtering Ion Plating (CFUBMSIP) has been used to deposit undoped and nitrogen doped NiAI thin films onto glass and stainless steel 316 substrates. These films have potential applications in tribological, electronic media and thermal barrier coatings. The surface characteristics, composition, mechanical and structural properties have been investigated using stylus profilometry, X-ray diffraction (XRD), Energy dispersive spectroscopy (EDAX), Atomic force microscopy (AFM) and nanoindentation. The average thickness of the films was approximately 1 microm. The X-ray diffraction spectra revealed the presence of the beta NiAl phase. The EDAX results revealed that all of the undoped and nitrogen doped NiAl thin films exhibited the near equiatomic NiAl composition with the best results being achieved using 300 Watts DC power for Ni and 400 Watts DC power for Al targets respectively. AFM results of both types of films deposited on glass samples exhibited a surface roughness of less than 100 nm. The nanoindenter results for coatings on glass substrates displayed hardness and elastic modulus of 7.7 GPa and 100 GPa respectively. The hardest coatings obtained were obtained at 10% of nitrogen.

Closed Field Unbalanced Magnetron Sputtering Ion Plating of Ni/Al Thin Films: Influence of the Magnetron Power

In this study NiAl thin films have been deposited using closed field unbalanced magnetron sputtering Ion plating (CFUBMSIP). The influence of magnetron power has been investigated using dense and humongous NiAl compound targets onto stainless steel and glass substrates. Potential applications include tribological, electronic media and bond coatings in thermal barrier coatings system. Several techniques has been used to characterise the films including surface stylus profilometry, energy dispersive spectroscopy (EDAX), X-Ray diffraction (XRD) Composition analysis of the samples was carried out using VGTOF SIMS (IX23LS) and Atomic force microscopy (AFM). Scratch tester (CSM) combined with acoustic emission singles during loading in order to compare the coating adhesion. The acoustic emission signals emitted during the indentation process were used to determine the critical load, under which the film begins to crack and/or break off the substrate. The average thickness of the films was approximately 1 um. EDAX results of NiAl thin films coating with various magnetron power exhibited the near equal atomic% Ni:Al. The best result being obtained using 300 W and 400 W DC power for Ni and Al targets respectively. XRD revealed the presence of beta NiAl phase for all the films coatings. AFM analysis of the films deposited on glass substrates exhibited quite a smooth surface with surface roughness values in the nanometre range. CSM results indicate that best adhesion was achieved at 300 W for Ni, and 400 W for Al targets compared to sample other power values. SIMS depth profile showed a uniform distribution of the Ni and Al component from the surface of the film to the interface.

Structural and tribological properties of CrTiAlN coatings on Mg alloy by closed-field unbalanced magnetron sputtering ion plating

In this paper, a series of multi-layer hard coating system of CrTiAlN has been prepared by closed-field unbalanced magnetron sputtering ion plating (CFUBMSIP) technique in a gas mixture of Ar + N 2. The coatings were deposited onto AZ31 Mg alloy substrates. During deposition step, technological temperature and metallic atom concentration of coatings were controlled by adjusting the currents of different metal magnetron targets. The nitrogen level was varied by using the feedback control of plasma optical emission monitor (OEM). The structural, mechanical and tribological properties of coatings were characterized by means of X-ray photoelectron spectrometry, high-resolution transmission electron microscope, field emission scanning electron microscope (FESEM), micro-hardness tester, and scratch and ball-on-disc tester. The experimental results show that the N atomic concentration increases and the oxide on the top of coatings decreases; furthermore the modulation period and the friction coefficient decrease with the N 2 level increasing. The outstanding mechanical property can be acquired at medium N 2 level, and the CrTiAlN coatings on AZ31 Mg alloy substrates outperform the uncoated M42 high speed steel (HSS) and the uncoated 316 stainless steel (SS).

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.

Structural, mechanical, and tribological studies of Cr–Ti–Al–N coating with different chemical compositions

In this paper, a multicomponent hard coating system of Cr–Ti–Al–N has been studied for its structural, mechanical and tribological properties under different chemical compositions. The coatings were deposited onto AISI M42 steel plates by closed-field unbalanced magnetron sputtering ion plating (CFUBMSIP) technique in a gas mixture of Ar + N 2. Three processing steps in deposition involved were plasma ion cleaning, buffer layer deposition, and multicomponent layer deposition. During the final deposition step, nitrogen concentration was controlled at ∼ 50 at.% by using the feedback control of metal plasma optical emission monitor (OEM). The metallic ratio of Cr, Ti, and Al was varied by adjusting the currents of different magnetron targets. The coatings were characterized by means of energy dispersive X-ray (EDX) analysis, X-ray photoelectron spectrometry (XPS), X-ray diffractometry (XRD), Rockwell-C indentation tester, microhardness tester, and pin-on-disc (POD) tribometer, in order to check their chemical composition, as well as to determine the structural, mechanical and tribological properties. The experimental results showed that the optimised quaternary Cr–Ti–Al–N coating performs better than the binary CrN as well as the ternary Cr–Ti–N and Cr–Al–N coatings in terms of hardness and wear resistance. The introduction of both Ti and Al elements into the CrN-based coatings enhances both of their mechanical and tribological performance.

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.

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

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.

Coating characteristics and tribological properties of sputter-deposited MoS 2/metal composite coatings deposited by closed field unbalanced magnetron sputter ion plating

As previously reported (V.C. Fox, N.M. Renevier, D.G., Teer, J. Hampshire, V. Rigato, Proceedings of the PSE Conference in Garmisch Partenkirchen, 14–18 September 1998, Germany, Surf. Coating Technol., in press) the properties of MoS 2 coatings deposited by closed field unbalanced magnetron sputter ion plating (CFUBMSIP) can be improved by the co-deposition of a small amount of titanium. These MoS 2/Ti composite non-multilayer coatings known as MoST™, are harder (10–15 GPa) and more adherent (critical load scratch above 120 N), much more wear resistant (10 −16–10 −17 m 3/mN), and higher load bearing (3.5 GPa) than pure MoS 2 coatings. They have similar low friction to pure MoS 2 coating (μ of 0.02 at 40% humidity) but are much less sensitive to atmospheric water vapour during tribological testing at high humidity. MoS 2/Ti composite coatings have given excellent industrial results for a wide range of cutting and forming applications. Other metal additions such as Cr, W, Mo and Zr have been studied with varying compositions and substrates. Laboratory test results using micro hardness and nanoindentation testing, scratch adhesion testing, pin on disc and reciprocating friction and wear tests are presented. Structural analysis was carried out using X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy of cross-sections through the coating. This paper presents further analysis on the MoS 2/Ti composite coatings and with other metal additions such as chromium, tungsten or zirconium.

Deposition and tribological behaviour of sputtered carbon hard coatings

The exceptional tribological properties of low deposition temperature sputtered carbon coatings (Graphit-iC coatings) have been recently reported. This paper describes the latest development of these coatings and particularly how, by an optimisation of the deposition parameters, it has been possible to obtain relative soft to very hard coatings with extremely low specific wear rates. The coatings have been deposited in a closed field unbalanced magnetron sputter ion plating (CFUBMSIP) installation. By applying the appropriate conditions of deposition, carbon coatings with hardness from 1500 to 4000 HV can be routinely deposited. Preliminary analytical results are presented in order to characterise such hard coatings: high-resolution transmission electron microscopy, scanning electron microscopy and X-ray diffraction analysis are some of the different techniques used for this work. Finally, a number of the applications are reported with tribological test results.

High performance sputtered carbon coatings for wear resistant applications

The Closed Field Un-Balanced Magnetron Sputter Ion Plating (CFUBMSIP) process is now routinely used in a production environment and is characterised by a high degree of flexibility in terms of the substrates and coating materials which can be used. Compared to classical magnetron sputtering the closed field system produces higher ion current density which gives high quality coatings and excellent adhesion. The ability to vary the deposition parameters over a wide range, permits the modification of not only the composition and the structure but also the morphology (density and growth mode) of the films. This paper describes, that in particular, a range of carbon coatings from transparent, electrically insulating to black, conductive coatings, can be produced. Tribological tests concerning adherence, hardness and wear properties in atmospheric and lubricated conditions are presented. The effects of the nature of the substrates with different hardness properties (M42, stainless steel and Al) are investigated.

Recipe Control for Closed-Field Unbalanced Magnetron Sputter Ion-Plating Machines

The requirements, specification and chosen implementation of a secure, reliable and compact process control system on a personal computer is described for automating closed-field unbalanced magnetron sputter ion-plating machines. The made-to-order nature of many such installations has consequences for the design of the control system, necessitating great flexibility and ease of reconfiguration. The system described has been implemented for the deposition of Al2O3, alloy nitride, ‘diamond-like’ carbon and other coatings. Examples are presented of the control script language and a typical mimic display.