Closed Field Unbalanced Magnetron Sputtering Research Articles

Construction of chromium coatings with (200) preferred orientation and exploration the high-temperature steam oxidation properties

In order to improve the high-temperature steam oxidation resistance of Zircaloy-4 for accident tolerant fuel claddings (ATF), Cr coatings with (200) preferred orientation were deposited by changing argon flow using closed field unbalanced magnetron sputtering. The influences of the argon flow on the microstructure and high-temperature steam oxidation properties of Cr coatings were studied systematically. The results indicate that Cr coatings exhibit obvious preferred orientation of Cr (200) especially for 30sccm argon flow due to more adatom easy aggregation on Cr (200) plane under more ion collisions. With the argon flow increases, the grains of Cr coatings gradually becomes compact and homogeneous, which causes the formation of thicker Cr2O3 oxide layer and residual Cr layer on Cr coatings surface after 1200 °C high-temperature steam oxidation test at 8h. Above all, Cr coatings prepared by 30sccm argon flow still possess excellent steam oxidation resistance properties even after 12h exposure time. In addition, the high-temperature steam oxidation mechanism of 30sccm argon flow Cr coatings under different exposure time also was discussed in detail. The study about Cr (200) preferred orientation is expected to provide a new research idea for prolonging steam oxidation resistance and accident tolerant time.

Low temperature quaternary hard coatings with Cr- to Ti-based transition composition

A new quaternary hard coating based on Cr/CrN adhesion layers and a TiCrAlN main coating layer was developed for low-temperature applications. It was deposited in a closed-field unbalanced magnetron sputtering equipment. The nanohardness, adhesion and thickness of the coating were characterized by Anton Paar’s nano-indenter tester, scratch tester and calotester. The chemical composition and surface morphology were investigated by a Hitachi SU 500 scanning electron microscope equipped with an energy dispersion analyzer. The coating showed a low coefficient of friction and a good adhesion strength between the substrate and the Cr/CrN transition layer, as well as between the transition layer and the TiCrAlN layer. The nanohardness achieved was 33 GPa. The research results showed that the quaternary Cr/CrN/TiCrAlN hard coating deposited at 200 °C has mechanical properties comparable to coatings with a similar composition deposited at standard deposition temperatures.

Influence of gradient interlayer thickness on corrosion and tribological behavior of Ti-containing multilayer graphite-like carbon films

Structural design is a crucial strategy to improve the service performance of amorphous carbon films in aggressive environments. In this study multilayered graphite-like carbon (GLC) films with adhesive layer/gradient interlayer/doping layer architectures with varied gradient interlayer thickness were deposited on 316L stainless steel substrates by closed field unbalanced magnetron sputtering. The effect of gradient interlayer thickness on microstructure, mechanical, tribological and corrosion behavior of the GLC films was investigated. The results show that the mechanical properties and bonding strength decrease with increasing gradient interlayer thickness due to the increased sp2 content, surface roughness and decreased film integrity. The friction coefficient curves in ambient air and 3.5% NaCl solution show similar three-stage feature with distinctive wear mechanism in stage III. The decreased mechanical properties and loose microstructure of GLC films with thicker gradient interlayer thickness caused the decreased wear resistance in both ambient air and NaCl solution. In comparison with the uncoated substrate, the GLC films show improved corrosion resistance in NaCl solution, which also decreases with the increased gradient interlayer thickness due to the low film compactness and high electrical conductivity.

Influence of substrate bias on the scratch, wear and indentation response of TiSiN nanocomposite coatings

TiSiN coatings were synthesised onto AISI M42 tool steel substrates via closed field unbalanced magnetron sputtering ion plating , using bias voltages of −40 and −50 V. The aim of this study is to investigate the underlying deformation mechanisms of TiSiN coatings, prepared at two different substrate bias voltages, following scratching, wear and indentation tests . A graded columnar microstructure evolved in these coatings. A hardness value of ~30.2 GPa was determined in the coating prepared at the lower bias voltage (i.e., −40 V), which was correlated to the fine nanocomposite structure and the presence of a high compressive residual stress. Of note, for the coating deposited at −40 V enhanced scratch adhesion strength , i.e., higher critical loads (L c1 and L c2 ) against cohesive and adhesive failure were determined with the higher H/E r and H 3 /E r 2 values. The improved scratch resistance was ascribed to the hierarchical structure that hindered crack propagation in the TiSiN coatings during progressive loading. An approximately 21% decrease in wear rate was obtained at the lower bias voltage, which was attributed to the slightly lower Si concentration (~8.3 at.%) and, in turn, higher hardness. Deformation behaviour under indentation loading was dominated by shear sliding along the columnar grain boundaries. • ~20% increase in L c1 was found in the TiSiN coating with the lower Si content. • The scratch resistance was enhanced by the coating's hierarchical structure. • ~21% reduction in wear rate was achieved in the coating with the lower Si content. • Indentation deformation was governed by columnar shear sliding.

Effect of Negative Bias Voltage on Tribological Properties under High Relative Humidity Environment and Corrosion Resistance of Boron Carbide Coatings

Humid air is a very important service environment, in which metal friction parts should be enhanced to offer excellent corrosion resistance and wear resistance. The B4C coating is an excellent candidate material to enhance the corrosion resistance and tribological behaviors. The purpose is to investigate the effect of negative bias voltages on the tribological properties of B4C coatings under a high relative humidity environment. Amorphous B4C coatings were successfully prepared by closed field unbalanced magnetron sputtering technology and its microstructure, hardness, elastic modulus, adhesive force and tribological properties were systematically studied. Results demonstrate that the B4C coatings deposited at each negative bias voltage have a columnar structure and the surface roughness remained unchanged (about 1.0 nm), while the thickness, hardness, elastic modulus and adhesion force increase first and then decrease with the negative bias voltage increasing. Among them, the B4C (−50 V) coating showed the best mechanical properties. It should be noted that the B4C (−50 V) coating with an excellent corrosion resistance also exhibits the lowest friction coefficient (~0.15) and wear resistance (7.2 × 10−7 mm3·N−1·m−1) under humid air (85% RH). This is mainly due to the tribochemical reaction of B4C during a sliding process to produce boric acid at the sliding interface. B4C coatings can provide an excellent corrosion resistance and high wear resistance due to their high chemical stability and high hardness.

Effect of rubber substrates on the flexibility and tribological properties of diamond-like carbon coatings

In this study, closed-field unbalanced magnetron sputtering was employed to deposit a diamond-like carbon (DLC) film with Cr as the middle layer on three elastomeric substrates, namely nitrile rubber (NBR), fluorine rubber (FKM), and ethylene propylene diene monomer (EPDM) rubber, respectively. In addition, effects of these rubber substrates on the structure and properties of DLC films were investigated. Results revealed that after the bending test, several new cracks are produced on the DLC-coated EPDM rubber and NBR rubber, while debonding is not observed, indicative of the good flexibility and adhesion of DLC films on EPDM rubber and NBR rubber. Furthermore, tribological properties of NBR rubber and EPDM rubber were significantly improved by the DLC film, and almost no film damage was observed on the wear track, while the DLC coated-FKM exhibited severe wear due to the gradual peeling of the coating. Film shedding was caused by the extremely smooth FKM substrate, which led to low film adhesion. Different tribological properties of the coated rubbers were closely related to the difference in surface roughness and mechanical properties of the rubber substrates. • Using unbalanced magnetron sputtering technology to deposit DLC with Cr as a interlayer on NBR, EPDM, FKM • The substrate roughness shows considerable influence on the adhesion. • The friction properties of coated NBR, EPDM and FKM are compared systematically.

Investigation of high potential corrosion protection with titanium carbonitride coating on 316L stainless steel bipolar plates

In order to improve the durability of stainless steel bipolar plates at high potential during the start-up/shut-down process of proton exchange membrane fuel cell (PEMFC), TiN and TiCN coatings with different C element contents are deposited on the 316L stainless steel substrates by using Closed Field Unbalanced Magnetron Sputter Ion Plating. The electrochemical test results show that the TiCN-2sccm sample possesses excellent corrosion resistance compared to other samples. The results of interfacial contact resistance (ICR) measurements show that the minimum ICR value of the TiCN-2sccm sample is 10 mΩ cm2, which meets the Department of Energy targets.

Tribocorrosion characteristics of CrMoSiCN/Ag coatings on Ti6Al4V alloys in seawater

CrMoSiCN/Ag coatings were deposited on Ti6Al4V alloys at the trimethylsilane flow of 15 sccm using closed-field unbalanced magnetron sputtering, and their microstructures were observed and analyzed using SEM, XRD, XPS and TEM, respectively. The coatings’ mechanical properties were measured using nano-indenter. The tribocorrosion characteristics of Ti6Al4V and CrMoSiCN/Ag coatings were investigated in seawater using tribocorrosion tester. The results revealed that the nanocomposite coatings consisted of (Cr, Mo)N solid solution, Ag nanocrystal and amorphous SiCNx matrix. As the Ag target current increased to 1.0 A, a large amount of Ag nanoparticles were observed on the coating surface. The coating hardness initially increased to 21.0 ± 0.7 GPa at the Ag target current of 0.4 A and then declined. After the Ag element was added into coatings, their tribocorrosion characteristics were improved. The tribocorrosion characteristics of coatings were much better than those of Ti6Al4V. The tribocorrosion characteristics of CrMoSiCN/Ag coating at the Ag target current of 1.0 A were the best in seawater.

TiN versus TiSiN coatings in indentation, scratch and wear setting

The indentation response, scratch behaviour and wear performance of binary TiN and ternary TiSiN coatings under a variety of loading conditions were comparatively studied. The coatings were fabricated onto M42 steel substrates via closed field unbalanced magnetron sputtering ion plating. A maximum hardness value of ~40 GPa was obtained for one of the TiSiN coatings as compared to ~28 GPa for TiN. This was attributed to the nanocomposite structure, grain refinement, solid solution hardening and the higher compressive residual stress in the ternary coatings. The damage resistance of both the TiN and TiSiN coatings under indentation loading was governed by the dampening effects of sliding or shearing of the columnar grains along the grain boundaries coupled with the coatings’ respective mechanical characteristics. Improved scratch adhesion properties (i.e., higher LC1, LC2 and CPR values) were also observed for the TiSiN coatings that were underlain by their superior mechanical properties along with the graded structure, promoting the capacity to resist crack formation and delamination. Lower wear rates for the TiSiN coatings during dry sliding were found to be consistent with their higher H/Er, H3/Er2 and We values.

Characteristics of Palladium Doped Amorphous Carbon Films Fabricated by Unbalanced Magnetron Sputtering System

Generally, hydrogenated amorphous carbon (a-C:H) has been shown to have a low friction coefficient, high hardness, and low abrasive wear rate. In this study, Pd doped hydrogenated amorphous carbon (a-C:H:Pd) fabricated by the closed-field unbalanced magnetron sputtering (CFUBMS) system with two targets of carbon and palladium in Ar/C2H2 plasma. The tribological and lubricant characteristics for a-C:H:Pd fabricated with various DC bias voltage from 0 to −200 V were investigated. We obtained a hardness up to 27.5 GPa and friction coefficient lower than 0.1. The atomic percentage of Pd related to the lubricant properties increased up to 22% at −200 V. In the results, the Pd doping in the a-C:H films improved the tribological and lubricant properties. The friction coefficient value of a-C:H:Pd films was decreased, the hardness and elastic modulus were increased, and also the adhesion properties was improved with the increase of negative DC bias voltage.

Microstructure and High-Temperature Friction and Wear Properties of CrAlMoN Film

Closed-field unbalanced magnetron sputtering ion plating was used to form CrAlMoN films on the surface of single-crystal silicon and tool steel. The composition and morphology of the films were determined through energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy. High-temperature friction and wear properties of CrAlMoN films were assed using a friction and wear tester and by studying the film cross-sections. The hardness of CrAlMoN films was determined using a nanoindenter. Results showed that CrAlMoN films have a nanomultilayer structure, with the same fcc structure as CrN. At room temperature, the hardness and wear resistance of CrAlMoN films are greater than that of CrAlN films. The friction properties of CrAlMoN films varied widely with an increase in the temperature. At 600 °C, the friction performance of CrAlMoN films degrades rapidly, and the degree of film wear is significantly increased. In contrast, CrAlN films retain high wear resistance at 600 °C.

Influence of Mo Doping on the Microstructure, Friction, and Wear Properties of CrAlN Films

In this study, closed-field unbalanced magnetron sputtering ion-plating technology is used to deposit CrAlMoN and CrAlN nanomultilayer films on the surfaces of M2 tool steel and single-crystal Si. Energy-dispersive spectroscopy, scanning electron microscopy, x-ray photoelectron spectroscopy, transmission electron microscopy, x-ray diffraction, scratch tester, nanoindenter, and pin-on-disk wear tester are used to study the influence of Mo doping on the composition, microstructure, mechanical properties, and friction properties of CrAlN films. Results show that CrAlMoN films have a nanomultilayer structure, CrN/Mo2N/CrN/AlN, with a modulation period of 10.5 nm. After Mo doping, the face-centered cubic structure of CrAlMoN films remains the same as that of CrAlN films. The chemical valence of each element in CrAlN films does not change with Mo doping. At room temperature, the wear resistance of CrAlMoN films is significantly improved compared with that of CrAlN films. This is attributed to the significant antifriction effect of MoO3 that forms on CrAlMoN films doped with Mo during the friction process.

Structure and adhesion properties of TiNi/MoS2 coatings

One of the most important features expected from protective coatings is good adhesion to the substrate. In this paper, TiNi/MoS2 functional solid lubricant coatings were deposited by closed field unbalanced magnetron sputtering system on 52100 and D2 steels. The adhesion and multipass scratch characterization of the coatings were investigated. The obtained results were analyzed in terms of deposition parameters, as well as structural and mechanical properties of the coatings. Adhesion properties of the coatings were determined by scratch tests with a progressive load. The fatigue-like behaviors of the coatings were obtained by the bidirectional multipass scratch test with a constant load. The results showed that the TiNi/MoS2 has high adhesion and multipass scratch resistance than the literature results. The coatings deposited on the 52100 steel yielded better performance.

Hardness, Adhesion, and Wear Performance of Duplex Treatment Coatings of Nitride/TiAlZrN with Different Zr Target Currents

The surface treatment, which includes first a thermal diffusion process, such as nitriding and then a physical vapor deposition coating process as the working layer, is called duplex treatment in the literature. In this study, the effects of the duplex treatment on the hardness, adhesion, and wear performance of TiAlZrN coatings on the hardened AISI H13 steel produced using the closed field unbalanced magnetron sputtering method with variable Zr target current (2 A, 3 A, and 5 A) were investigated. Within the scope of these investigations, scanning electron microscope, x-ray diffracrometer, optical microscope, optical profilometer, energy-dispersive spectrometer, micro- and nano-hardness, scratch, and wear tests were used. In micro- and nano-hardness tests, it was determined that the hardness of the substrate increased significantly (approximately 400%) owing to the duplex treatment. In addition, with the increase in the Zr target current, it was observed that the hardness of the coatings was in an increasing trend. Adhesion strength increased with the enhancement of both the hardness of the substrate and the coatings. It was beheld that the adhesion strength of the coatings increased with the duplex treatment. Besides, the coating produced using the highest Zr target current reached maximum adhesion strength of 79 N in relation to superior hardness. Wear performance of the samples was determined using a ball-on-disk tribometer. As a result of wear tests, TiAlZrN coatings with duplex treatment were observed to notably improve the wear performance of the substrate material by 95 times. The effects of Zr target current on the wear performance of the coatings were similar to those of hardness and adhesion strength.

Сравнительная оценка триботехнических характеристик твердосмазочных покрытий, нанесенных методом замкнутого поля несбалансированного магнетронно-ионного распыления, для различных условий функционирования

This paper presents a comparative assessment of the tribotechnical characteristics of friction pairs with solid lubricant coatings (SLC) based on the MoS2 suspension application of VNII NP 212 and SLCCFUBMSIP deposited by the closed field unbalanced magnetron sputter ion plating (CFUBMSIP) of combined compositions MoS2+Ti, MoS2+Zr, MoS2+Cr , MoS2+W. It was established that under normal atmospheric conditions in the friction modes corresponding to the contact friction temperature of 157 °С, the life of SLCCFUBMSIP was 42.1% higher, and the coefficient of friction (ffr) was on average 2 times lower than that of SLC VNII NP 212. The average value of the life reduction coefficient for SLCCFUBMSIP during the transition from normal atmospheric conditions to water was 2.98. Under normal atmospheric conditions and in water, the SLCCFUBMSIP coefficient of friction was in the range of 0.02–0.04, and in an oil environment it ranged from 0.03 to 0.08. SLCCFUBMSIP based on pure MoS2 in normal atmospheric conditions, in water and oil was practically unusable.

Enhancing the adhesion strength and wear resistance of nanostructured NiCrN coatings

NiCrN coatings, with varying Ni contents, were deposited on AISI M2 tool steel substrates using closed field unbalanced magnetron sputtering ion plating (CFUMSIP) where the NiCr target current (INiCr) was varied. An evolution of the graded columnar structures was found in these coatings, where increased incorporation of nickel induced grain refinement, as well as a reduction in values of both hardness (H), elastic modulus (Er) and elastic recovery (We). The influence of variations in the microstructure and mechanical properties on the adhesion behaviour and tribological performance of these NiCrN coatings was investigated. Scratch test results demonstrated that higher critical loads (Lc1 and Lc2) suppressed both cohesive and adhesive failure in coatings which exhibited higher values of H/Er, H3/Er2 and We. The failure mode under progressive scratch loading was controlled by the hierarchical design of the NiCrN coatings that enhanced adhesion and prevented crack propagation through the coating. For the coatings with lower Ni contents improved wear resistance was ascribed to not only higher H/Er, H3/Er2 and We values of these coatings, but also the graded interlayers that delocalised the stress distribution during dry sliding.

Comparative study on microstructure, bio-tribological behavior and cytocompatibility of Cr-doped amorphous carbon films for Co–Cr–Mo artificial lumbar disc

Cr-doped amorphous carbon (a-C:Cr) film is a promising protective coating to extend the lifetime of Co–Cr–Mo implants. Here, a-C:Cr films with the same doping concentration of Cr and thickness are deposited on Co–Cr–Mo substrates using the closed-field unbalanced magnetron sputtering (UBMS) and the plasma-enhanced chemical vapor deposition (PECVD) methods. A comparative study on the microstructure, bio-tribological behavior, and cytocompatibility of two kinds of a-C:Cr films in the air and different simulated body fluids is conducted. Microstructural analysis results show that the a-C:Cr films prepared by UBMS and PECVD methods belong to graphite-like carbon (GLC) and diamond-like carbon (DLC) films, respectively. Nanohardness of the UBMS a-C:Cr film is found to be lower than that of the PECVD counterpart. However, the UBMS a-C:Cr film exhibits better lubrication, lower wear depth and lower wear volume under all the three simulated body fluids, because of the slight polishing wear and boundary lubrication mechanisms. Moreover, both kinds of a-C:Cr films significantly improve the cytocompatibility of Co–Cr–Mo substrate alloy.

Harmonizing mechanical responses of nanostructured CrN coatings via Ni additions

CrN coatings are often brittle and prone to abrupt failure. Incorporation of Ni is known to have significant effects on the chemical composition, microstructure and mechanical behaviour of chromium nitride coatings synthesised by PVD, and thus imparting toughness. In this study, a series of NiCrN coatings, with varying Ni concentrations, were deposited onto AISI M2 tool steel substrates through closed-field unbalanced magnetron sputtering ion plating (CFUMSIP). The phase compositions, microstructure, mechanical properties and deformation behaviour of the coatings were characterised by XRD, AFM, FIB, TEM/EDS and indentation testing. Residual stresses of these as-prepared coatings were measured by the XRD-sin2ψ method. A columnar structure was observed in all coatings, although grain refinement at higher NiCr target currents was noted. High hardness values of ~20 GPa were found in the coatings with the lower Ni (~5–14 at%) contents, associated with the effects of solid solution hardening, high compressive residual stress and grain refinement. Moreover, significant damage-tolerance, coupled with good hardness values (greater than ~12 GPa), was found in the NiCrN coatings deposited at INiCr ≥ 2 A. The presence of a metallic nickel-rich phase, together with nanoscale porosity, may contribute to stress dissipation and help maintain structural integrity.

High-Temperature Oxidation Resistance of CrMoN Films

The CrMoN film is deposited on the surface of M2 tool steel using the closed-field unbalanced magnetron sputtering technology. We measured the surface morphology, composition, phase structure, hardness and film/base bonding strength of CrMoN film using a scanning electron microscope, x-ray diffractometer, nano-indenter and scratch tester after oxidation at room temperature, 500, 600, and 700 °C for 1 h. The results of this study demonstrated that the crystal structure and mechanical property of CrMoN film at room temperature are maintained after oxidation at 500 °C for 1 h. In addition, with the increase in oxidation temperature, there is an increase in the evaporation of MoO3 on the film surface and the oxidation degree of the film along with the appearance of fine pores. Moreover, the mechanical property and film/base bonding strength of CrMoN film significantly decrease after oxidization at 700 °C for 1 h.

Effect of chromium doping on high temperature tribological properties of silicon-doped diamond-like carbon films

Amorphous carbon films were deposited by means of closed-field unbalanced magnetron sputtering (CFUBMS). The silicon content was fixed at 1.3 at. %, while the chromium content was increased by modification of the current applied to the chromium magnetrons, with two doping levels, 0.3 and 2.7 at. %. Both, hardness and thermal stability were found to decrease as result of increasing chromium. Ball-on-disk tests revealed friction coefficients of 0.06 at room temperature with similar specific wear rate in all films (~4 × 10−13 m3 N−1 m−1). Increasing annealing temperatures were found to reduce the coefficient of friction compared to room temperature values, while increasing the specific wear rate for all films.