Unbalanced Magnetron Sputter Ion Plating Research Articles

Research on Microstructure and Tribological Properties of Cr-Based Hard Coatings

In this paper, three kinds of Cr-based hard coatings have been studied for its structural, mechanical and tribological properties at room temperature. By the technology of closed field unbalanced magnetron sputter ion plating (CFUMSIP), CrN CrAlN and CrTiAlN hard coatings were deposited onto DC53 cold die steel and silicon (100) substrate. The coatings were characterized by means of field emission scanning electron microscopy (FESEM), X-ray diffractometer (XRD), microhardness tester, optical microscope and ball-on-disc tribometer, in order to check their structural, as well as to determine the mechanical and tribological properties. The experimental results showed that the CrTiAlN coating performed better than the CrN coating and the CrAlN coating in terms of mechanical and tribological properties. The wear resistances of CrN, CrAlN and CrTiAlN coatings have been significantly improved compared with DC53 steel substrate.

Study on Electrochemical Corrosion Behavior Comparison between DLC and TiN Coatings under Different Corrosive Environment

Diamond-like carbon (DLC) and TiN coatings were deposited on the 304 austenitic stainless steel(SUS304) substrates by using unbalanced magnetron sputtering and arc ion plating techniques, respectively. The phase structure and surface morphology of coatings were characterized by SEM and XRD.The electrochemical corrosion of two coatings in different electrochemical solutions (including3.5%NaCl,10%HCl,20%NaOH) were investigated by electrochemical workstation.The result showed that DLC coating was amorphous structure and TiN coating was nano-crystalline structure.The surface of DLC coating was smooth and dense,while TiN coating existed pits.In 10%HCl and 3.5%NaCl solutions,the corrosion resistance of DLC coating increased by 4.16 and 10.9 times compared with SUS304 and increased by 5.16 and 1.11 times compared with TiN coating,respectively.But in 20%NaOH solution, the corrosion resistance of DLC was not superior to SUS304 and TiN coating.In 10%HCl solution,the corrosion resistance of TiN coating increased by 9.81 times compared with 304 SUS304.But in 3.5%NaCl and 20%NaOH solutions,the corrosion resistance of TiN coating was worse than SUS304.

Development of advanced duplex surface systems by combining CrAlN multilayer coatings with plasma nitrided steel substrates

Both modelling analyses and experimental work have recently confirmed that the failure of thin coatings on steel, especially under high loads for some demanding applications, is related to the lack of mechanical support from the substrate, which means that the exceptional hardness, toughness and wear resistance of state of the art PVD coatings cannot be fully exploited. To this end, two types of new duplex surface systems have been developed from this research: i) PVD (specifically Closed Field UnBalanced Magnetron Sputter Ion Plating, CFUBMSIP) CrAlN multilayer coating deposited on ex-situ, 20-h active-screen plasma nitrided (ASPN) steel samples, and ii) in-situ 3-h, high power medium frequency pulsed plasma nitriding (HPMFPPN) treatment, followed by a similar CrAlN coating, but performed in a serial, single batch process in an otherwise conventional CFUBMSIP equipment. The microstructures of these two duplex surface engineered systems were characterised using XRD and SEM, while their hardness, adhesion, load bearing capacity and tribological properties were compared by micro-hardness tests, scratch adhesion tests and pin-on-disc sliding wear measurements. Post-test examinations were conducted and the results confirmed that a hard coating on a nitrided substrate can fully exploit the advantages of both the nitrided sub-surfaces for increased load bearing capacity and of the PVD coating for increased hardness, high temperature stability and extreme wear resistance. Finally, the advantages and disadvantages of these two new duplex surface systems were compared and their potential applications were discussed.

Research on Microstructure and Tribological Properties of the Cp/AlSn Coatings Deposited by Magnetron Sputtering

The influences of microstructure and tribological properties of Cp/AlSn (Cp: carbon particule) composite films were applied to AlZn4.5Mg bearing alloy substrates using the closed-field unbalanced magnetron sputtering ion plating technique. The microstructure, phases and bond states of the coatings were separately characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The friction coefficients were measured using a pin-on-disc set-up. Results showed that the grain size and roughness of the films both decreased with increasing of carbon target current (IC) from 0.2 A to 0.8 A. Phases in the films were Al, Sn and C, although the films transformed from a crystalline state to amorphous when the carbon target current was applied. Al and Sn existed as pure metals. Carbon, composed of sp2and sp3bonds, mainly as sp2bonds, provided transfer films to reduce the friction coefficient of the films from 0.35 to 0.15. The specific wear ratio was a minimum, when the carbon target current was 0.4 A.

Raman analysis of DLC and Si-DLC films deposited on nitrile rubber

In this study a hybrid diamond-like carbon (DLC) and silicon doped diamond-like carbon (Si-DLC), with and without Si–C interlayers, were deposited onto nitrile rubber substrates. The deposition was done in a closed field unbalanced magnetron sputtering ion plating (CFUBMSIP) rig in Ar/C4H10 plasma. A combination of visible (488nm) and ultra-violet (UV; 325nm) Raman analysis was used to determine the G-peak dispersion of the films. Raman analysis was also used to estimate the hydrogen concentration and residual stress in the films. Calculated hydrogen values for all of the films were between 26 and 31%. The residual stress estimates of the films indicated that the inclusion of Si dopant and Si–C interlayers reduced compressive stress in these films. Raman analysis of the wear tracks indicated an increase in the G-peak position which could indicate that graphitization occurred during pin-on-disc experiments.

Effect of CrTiAlN Coatings on High-Temperature Oxidation Behavior of H13 Steel

CrTiAlN hard coatings have been deposited on H13 steel for improving the oxidation resistance by Closed Field Unbalanced Magnetron Sputter Ion Plating (CFUMSIP). The phase components, surface and section morphology of H13 steel before and after oxidation were analyzed by XRD and SEM. The results showed that the columnar crystal film possesses three major parts, i.e., the internal Cr bonding layer, the intermediate CrN transition layer, the external CrTiAlN gradient coating. The selective oxidation of Cr element was found on the surface of uncoated H13 steel while oxidation, but a continuous protective layer was not formed because of low Cr content, finally a lot of alpha Fe2O3 particles took place on the surface of H13 steel owing to the oxidation of the matrix element. O element can diffuse much more easily through the coating and oxide scales at 800 °C, and spallation and cracks were not found during the oxidation. These results indicated that the CrTiAlN coating have excellent high-temperature oxidation resistance at 800 °C.

Composition optimization of multilayered chromium-nitride–carbon film on 316L stainless steel as bipolar plates for proton exchange membrane fuel cells

The composition of multilayered chromium-nitride-carbon (Cr-N-C) film has great influence on the performance of coated 316L stainless steel (SS316L) as bipolar plates for proton exchange membrane fuel cells (PEMFCs). In this study, five films with different composition are deposited by closed field unbalanced magnetron sputter ion plating (CFUBMSIP) and the influence of nitrogen content adjusted by a closed-loop optical emission monitor (OEM) is evaluated. The phase structure and chemical composition of the films are characterized by X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). Interfacial contact resistance (ICR) between coated samples and gas diffusion layer (GDL) is measured. Potentiodynamic and potentiostatic tests are conducted to evaluate the corrosion resistance of coated samples. Experimental results show that Cr-N-C film with OEM setting of 60% presents the best performance, i.e. the ICR reduces to 2.11 mΩ cm2 under a compaction pressure of 1.4 MPa, and the corrosion current density reaches 0.308 μA cm−2 in the PEMFCs cathodic environment (0.5 M H2SO4 + 5 ppm HF solution at 70 °C, 0.6 V vs. SCE). Therefore, this study indicates that Cr-N-C film with OEM setting of 60% achieves optimal film composition and may be practically applied for commercialization of PEMFCs technology.

Properties of carbon film deposited on stainless steel by close field unbalanced magnetron sputter ion plating

Carbon films are deposited on 304 stainless steel (SS304) by close field unbalanced magnetron sputter ion plating using different substrate bias voltages and target currents to improve the corrosion resistance and electrical conductivity of bipolar plates made of SS304 in proton exchange membrane fuel cells (PEMFCs). The surface morphology, Raman scattering spectra, corrosion resistance, interfacial contact resistance (ICR), and contact angle with water of the carbon films are determined. A dense carbon film is produced on the SS304 by this technique and the corrosion resistance is improved significantly. The ICR value diminishes drastically and water contact angle increases after deposition. In addition, the passive current density in the simulated PEMFC environment decreases initially, increases as the substrate bias voltage is increased, and drops with decreasing target current. As the substrate bias is increased, the ICR between the carbon film and carbon paper exhibits an initial diminishing trend and then increases, but the effect of the target current on the ICR is not as substantial as that of the bias voltage.

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.

Influence of Carbon Doping on Microstructure and Tribological Properties of CrN Coating

The influence of carbon doping on tribological properties of CrCN Coating was studied through preparation of coatings deposited on single crystal silicon and M2 high speed steel(HSS) substrate using closed-field unbalanced magnetron sputtering ion plating technique. The friction coefficients were measured by pin-on-disc set-up. The microstructure and bond states of the coatings were characterized by X-ray diffraxtion(XRD), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS). The results show that the friction coefficient of coating decreases from 0.75 to 0.38, the microhardness increases from 1930HV to 2302HV, and the specific wear ratio of the coatings decreases from 8.35110-5m3/Nm to 3.85910-5m3/Nm with the increasing of carbon target current(IC) from 0A to 1.5A. The analysis of microstructure shows that the coatings transform from crystalline state to amorphous state and the grain size of the coatings decreases with the increasing of carbon target current.

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.

Development of Zr-Ti-N Coatings for Micro Drills for Machining of PCBs

A group of Zr-Ti-N coatings was prepared and studied to access their potential as a protective layer for micro drills to obtain cutting tool wear improvement. The coatings were grown using an industrial-scale four-target closed-field unbalanced magnetron sputtering ion plating system, employing one Ti and three Zr targets working in residual N2 atmosphere. To achieve Zr-Ti-N coatings with varying Ti doping content, the current applied to the Ti target was subjected to change from 0A to 3.6A while those to the Zr targets were kept constant. The coatings were characterized using GDOES, XRD, SEM, Vickers microhardness tester, scratch tester and Rockwell C indentation tester. Evaluation of wear improvement by Zr-Ti-N coatings for microdrills was conducted by machining of FR4 print circuit boards. It was found that the coatings with 16.5 at.% Ti doping content showed the highest microhardness and wear improvement for microdrills. Wear of microdrills with this coating could be reduced by a factor of two as compared with traditional TiN coated ones.

C/CrN multilayer coating for polymer electrolyte membrane fuel cell metallic bipolar plates

The two most important issues that plague wider use of stainless steel bipolar plates in polymer electrolyte membrane fuel cells (PEMFCs) are insufficient corrosion resistance and surface conductivity. In this study, C/CrN multilayer coatings are deposited on 316L stainless steel samples by close-field unbalanced magnetron sputtering ion plating. SEM shows that the C/CrN coatings are dense, continuous, and composing of carbon granules on the surface. Raman spectroscopy reveals an amorphous structure with a large sp2 constituent. The corrosion resistance and interfacial contact resistance (ICR) are investigated systematically. A superior ICR in the range of 2.6–2.9mΩ-cm2 at a compaction force of 150N/cm2 is achieved and it is even better than that of graphite. The deposited film possesses high chemical inertness thereby significantly enhancing the corrosion resistance of the coated SS316L. A thickness of 800nm is sufficient to protect against corrosion. C/CrN multilayer coatings are beneficial in that it can lead to a faster PVD deposition process and lower material cost, while permitting a superior performance in terms of surface conductivity and corrosion resistance.

Effect of plasma nitriding on adhesion strength of CrTiAlN coatings on H13 steels by closed field unbalanced magnetron sputter ion plating

A duplex treatment, i.e. plasma nitriding followed by closed field unbalanced magnetron sputter ion plating, is used to strengthen the bonding of CrTiAlN coatings to H13 steels in the paper. A nitride layer is first formed on H13 steel samples by plasma nitriding and then two chromium transition layers are prepared on the surface of the nitrided H13 steels using closed field unbalanced magnetron sputter ion plating. The adhesion between the substrate and the coating is evaluated using the Rockwell indentation and scratch tests. Meanwhile, the composition, phase structure and the morphologies for CrTiAlN coatings as well as the worn surfaces are characterized by EDX, SEM and XRD, respectively. Dry sliding wear behavior of the duplex-treated H13 steels is analyzed by using ball-on-disk wear tests compared with those of untreated and plasma-nitrided H13 steels. The results show that the adhesion strength and wear resistance for duplex-treated coatings increase significantly due to a gradient-hardness support, one favorable gradient of chemical composition, an intermediate hardening effect and a diffusion reaction of the nitrided layer-coating interface.

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.

Study on Properties and Preparation of Films by Unbalanced Magnetron Sputtering

TiAlN films were prepared by closed field Unbalanced Magnetron Sputtering ion plating. EDS, XRD and SEM were used to test the films’ chemical composition, microstructure and surface morphology. In addition, the films’ surface microhardness, bonding strength and friction coefficient were also determined. The experimental results indicate that the TiAlN films of different substrate hardness have dense film structure and the same chemical composition, the hard substrate microhardness of the film can reach 2575 HV0.025 and soft substrate can be up to 2295 HV0.025, the bonding strength of which is respectively 59N and 56N, Friction coefficient is 0.45 and 0.5.

Adhesion and composite micro-hardness of DLC and Si-DLC films deposited on nitrile rubber

Thin films of hydrogenated diamond-like carbon (DLC) and silicon (Si) doped diamond-like carbon (Si-DLC) have been deposited on acrylonitrile butadiene rubber (NBR) using a closed field unbalanced magnetron sputtering ion plating system. A sputter cleaning process was integrated into the deposition process so as to reduce the likelihood of re-contamination between the cleaning and deposition stages. The deposited coatings showed excellent adherence with an adhesion rating of 4A for films with a Si-C interlayer. The composite micro-hardness was highest for DLC films at 15.5GPa for indentation load of 147.1mN using a Vickers micro-hardness tester. Tribological tests undertaken under normal load of 5N using a pin-on-disc tribometer for all of the samples of DLC and Si-DLC films, with and without Si-C interlayer, show a friction increase between 0.25 and 0.4 to between 0.45 and 0.6. This friction increase has been related to the micro-hardness of the films.

Characteristics and tribological performance of DLC and Si-DLC films deposited on nitrile rubber

The characteristics and tribological performance of DLC and Si-DLC films with and without Si–C interlayers were studied in this paper. The films were deposited on nitrile rubber using a closed field unbalanced magnetron sputtering ion plating system. The film properties and characteristics were determined by scanning electron microscopy (SEM), hydrophobicity studies, Raman spectroscopy and tribological investigations. Tribological performance of these films was investigated using a pin-on-disc tribometer under applied loads of 1N and 5N under conditions of dry and wet sliding. The effect of immersing the films in water on tribological performance was also examined. The results show that the morphology of the films had a crack-like network. At a substrate bias of −30V, the coatings were characterised by a very dense non-columnar microstructure. The highest value of the ratio of intensities of the D and G peaks (ID/IG) was 1.2 for Si-DLC film with Si–C interlayer. The lowest value of 0.7 was observed for DLC film. The contact angle (CA) of water droplets showed that the films were hydrophobic. These results are interpreted in terms of hybridisation of carbon in these coatings. The tribological investigation showed a dependence on both the tribological condition under investigation and the atomic percentage of Si in the films. At 5N normal load the lowest wear depth was observed for DLC films.