Search

CrAlN coatings were synthesized on pre-plasma nitrided M2 high speed steels using different ion current densities. The effect of plasma nitriding pretreatment on the microstructures and tribological properties of composite CrAlN coatings had been studied. The results showed that the nitriding efficiency could be significantly enhanced by higher ion current density. The thickness of nitrided layer increased from 43 μm to 63 μm with the increase of ion current density. The nitrided layers without either compound layer or grain boundary precipitation were produced with all experimental ion current densities. Radial cracks also appeared at the Rockwell-C indentation edge of the composite CrAlN coating due to the conformal effect. Moreover, radial cracks of the composite coatings originated from the hard and brittle nitrided layer. The highest interfacial adhesion of the composite CrAlN coating reached 105 N. Furthermore, the wear resistance of CrAlN coating was improved by combining nitriding pretreatment with coating deposition, and the composite coating (PN4/CrAlN) possessed the superior wear resistant.

Microarc oxidation (MAO) is a popular surface treatment process to generate oxide coatings with excellent mechanical properties on valve metals. As a plasma discharge technique, the discharge mechanism in MAO is different from that in the bipolar plate. Due to the alternating arcs and multiple electrolytes in MAO, it is difficult to control and optimize the coating properties. Based on the arcing mechanism and ion motion, the boundary conditions of no-arc discharge, alternating arc discharge, and continuous arc discharge are derived, and the relationship between the discharge current and breakdown current and sustained arc current is investigated. For the same electrolyte, the boundary conditions are determined by equivalent concentration and conductivity. The results show that in the stable alternating arc discharge regime, the higher the concentration and smaller the conductivity, the more intense is the discharge. According to the boundary conditions, MAO experiments are designed using phosphate electrolytes to improve the hardness of oxide coatings. By selecting electrolyte characteristics close to the continuous arc discharge boundary in the stable alternating arc discharge regime, the arc discharge is most intense and brightest and the largest energy is transferred to the Al2O3 coating. Consequently, the crystallinity and mechanical properties are improved significantly.

CrN/AlCrN nano-multilayer films can combine the advantages of CrN and AlCrN films through film structure modulation using multi-arc ion plating technique. Auxiliary enhanced magnetic field may improve arc spots velocity and be beneficial to flexible structure modulation in this paper. An inductance coil was installed behind the CrAl target to further enhance the magnetic field. Then, CrN/AlCrN nanoscale multilayers were deposited on the single crystal silicon, M2 high-speed steel and the 304 stainless steel samples by the magnetic field enhanced multi-arc ion plating technique. The morphology and crystal structure of the film after deposition were analyzed, and the effects of magnetic induction intensity under different coil current on the bond strength, wear resistance, hardness and corrosion resistance of the film were studied. The results show that the number of large particles on the surface of the film is significantly reduced compared with that without magnetic field enhancement. The crystal structure of the thin film is a rocksalt-type cube with (111) and (311) preferred orientations. At the same time, increasing the coil current can improve the film compactness. With the increase of coil current from 0.3A to 1.2A, the microhardness and corrosion resistance of the film are improved due to the compact structure. However, the bond strength increases first and then decreases due to the increase of the stress caused by excessive ion impact. The friction coefficient and wear width of the film are the minimum when the coil current is 0.6A.

Pulse-enhanced vacuum arc evaporation (PEVAE) is promising in surface engineering and produces coatings with better structure and properties. In PEVAE, the target-to-substrate distance (Dt-s) affec...

The mechanical and tribological characteristics of titanium–aluminum nitride films deposited by the reactive magnetron sputtering of Ti–Al mosaic targets with different aluminum concentrations were studied. The dependences of the elemental composition, microhardness, and friction coefficient on the degree of doping of the films with aluminum and nitrogen concentration in the Ar/N2 gas mixture during film deposition were obtained. It was found that an increase in the aluminum content in the film results in an increase in film hardness and decrease in the friction coefficient. The optimum nitrogen concentration in the film was achieved at maximum hardness and low values of the friction coefficient. A maximum hardness of 23.5 GPa and a minimum friction coefficient of 0.082 were obtained for films of the composition Ti5AlN1.33, which had a Ti/Al ratio of 5 : 1 and a nitrogen deficiency.

In physical vapor deposition (PVD), the energy and incident angle of ions can be adjusted easily by applying an electromagnetic field so that coatings with different structures and properties can be produced. In this work, several high-ionization coating techniques are employed to deposit TiAlN coatings to compare the effectiveness of each technique and resulting coating properties. The continuous high-power magnetron sputtering (C-HPMS) technique shows advantages in the deposition rate and coating performance. In addition, a deposition rate of 400 nm/min is achieved by C-HPMS, whereas those of high power impulse magnetron sputtering (HiPIMS) and arc ion plating (AIP) are 85 nm/min and 225 nm/min, respectively. The coating also shows a particle-free and dense morphology with a smaller surface roughness of 22.4 nm. Owing to efficient ionization, the TiAlN coating deposited by C-HPMS has a high hardness of 33.2 GPa which is comparable to those prepared by AIP and HiPIMS but with small residual stress. The results provide valuable information on how to choose the proper techniques and parameters to produce coatings with the desirable adhesion strength, tribological properties, as well as corrosion resistance.

A home-made straight-duct filter cathodic vacuum arc system was used to synthesize tetrahedral amorphous carbon (ta-C) films. The ta-C films were fabricated using both direct-current cathodic arc evaporation (DC-CAE) and pulse-enhanced cathodic arc evaporation. A series of films were prepared as a function of pulse current ranging from 500 to 1000 A compared with 80 A direct current. The introduction of pulse current could markedly increase instantaneous input power (Wiip). The pulse-enhanced Wiip led to the increase in average substrate current from 0.46 to 1.07 A. Moreover, compared with DC-CAE, the pulse current of 1000 A significantly increased the intensity ratios of C II/(C I + C II) and C II/Ar II by about 65% and 130%, respectively. All the results showed that the pulse-enhanced Wiip substantially improved the evaporation and ionization rate of graphite. However, due to thermal-induced graphitization conversion, the threshold pulse current was 800 A. Under this pulse current, the film exhibited the smallest ID/IG (0.26) as well as the highest sp3 fraction (64.3%). Correspondingly, the highest hardness (≈40 GPa) and the preferable toughness (H/E* of 0.12 and H3/E*2 of 0.52) were simultaneously achieved.

Pulse-enhanced vacuum arc evaporation (PEVAE) which combines pulsed and direct current operation of the arc source is a new method in cathodic arc evaporation technology. One advantage is t...

Micro-arc oxidation (MAO) is a popular coating technology for aluminum alloys, but the wear resistance and friction properties are limited by the intrinsic properties of the alumina coatings with high friction coefficients. In this work, CePO4 is identified as a quasi-2D material by the first principle calculation. As a self-lubricating phase, it is firstly formed in situ during the oxidation process and the lubrication mechanism is investigated. Nano-grains of cerium phosphate are formed and imbedded uniformly in the alumina coatings. With increasing Ce contents, the friction coefficients diminish to 0.1–0.15 during the 5-h test without obvious fluctuation. The results reveal the new concept of using self-lubricating additives in MAO oxide on Al alloys to improve the durability and mechanical properties.

Aluminum alloys are widely used in the aerospace and transportation industries, but the corrosion resistance is insufficient in long-term service especially in the high salinity environment. A ceramic coating composed of ZnO nanoparticles is demonstrated to significantly improve the corrosion resistance of the Al alloys. Owing to the similar chemical activity of Zn and Al, ZnO particles fuse into Al2O3 in the micro-arc during plasma electrolytic oxidation (PEO) rendering the coating compactness. The formation mechanism of the PEO coating is investigated and discussed. The corrosion current of the ZnO modified PEO coating is 4 orders of magnitude less than that of the LY12 substrate. Immersion tests performed in 3.5 wt% sodium chloride show that incorporation of ZnO prevents destruction and dissolution of the PEO coating in the high salinity environment.

Ti-Al-Cr-N films were fabricated on the surface of Si (100) wafers and M2 high speed steel by electrically enhanced discharge cathodic arc technology. The effect of the current of additional anode on plasma discharge, microstructure, hardness and adhesion strength has been investigated systematically. The results show that the discharge of additional anode can improve substrate current distinctly and mainly affects the excitation and ionization of nitrogen, rather than that of metal. Besides, the enhanced discharge can increase the ratio of substrate ion current to thickness of films (Ebi). The Ti-Al-Cr-N film deposited at the current of additional anode of 30 A possesses the highest nanohardness (31.3 GPa), the best adhesion strength between film and substrate (HF1), and the maximum H/E⁎ and H3/E⁎2 of about 0.081 and 0.25, respectively. Further increasing the current of additional anode to 40 A, the properties would deteriorate due to the precipitation of w-AlN (wurtzite structure) induced by ion irradiation effect.

In the PVD processes, the clearance of the chamber wall directly affects the microstructure and surface properties of the coatings. The (Ti,AlCr)N coatings are fabricated on M2 high-speed steel (HSS) and Si (100) by cathodic arc evaporation with the vacuum chamber cleaned or uncleaned. With the chamber cleaned, the arc discharge was enhanced with a higher intensity of optical spectrum and the concentration of residual oxygen was decreased. The clearance of chamber wall altered the external behavior of power supply and a larger input power was achieved. The average substrate ion current was increased by 13.0% and a larger Ebi was observed implying increased densification of coatings. A thicker coating was obtained with less surface defects (macroparticles). Consequently the microstructure and surface properties of (Ti,AlCr)N coatings have been improved with higher hardness, lower friction coefficient and superior adhesion strength between the coatings and substrate.

The ta-C coatings were fabricated using electromagnetically enhanced cathodic arc. The effect of auxiliary magnetic field generated by electromagnetic coil on arc discharge, microstructure and mechanical properties was investigated. The microstructure and mechanical properties were analyzed by SEM, Raman spectroscopy, XPS and Nano-indentation. The results demonstrated that average substrate current increased by about 4.3 times and sample temperature increased to 143.6 °C with the coil current increasing from 0 to 0.5 A. The coil current of 0.3 A led to the highest deposition rate of 8.2 nm/min, the highest amount of sp3 content of about 60% and the lowest ratio of ID/IG (0.36). The hardness of about 24 GPa and the preferable toughness (H/E of 0.11 and H3/E2 of 0.3) were achieved. A larger coil current led to a lower deposition rate due to the re-sputtering effect and the decreased sp3 content owing to larger heat effect.

The high ion energy produced by the substrate bias is essential to the enhancement of the sp3 content in diamond-like carbon (DLC) coatings and adhesion with the substrate. However, excessive ion energy can turn into heat conversely converting sp3 into sp2 undermining the mechanical properties. In this work, pulsed kV bias is applied to increase the carbonous ion energy to increase the sp3 content in DLC coatings and improve the adhesion with the substrate simultaneously while avoiding adverse temperature increase. The high ionized carbonous ions flux is formed by an anode-layer ion source with C2H2 gas and Cr/CrCx/CrC interlayers are introduced between the DLC coating and high-speed steel (HSS) substrate to release the internal stress by high-power impulse magnetron sputtering (HiPIMS). The DLC coatings not only have a large sp3 content, high hardness of 18.5 GPa, a low friction coefficient of 0.12, superior anti-corrosion behaviors,and wear rate of 0.87 × 10−15 m3/N m for 4 h, but also exhibits outstanding adhesion (Lc = 76 N) with the HSS substrate in spite of a DLC coating thickness of 13 μm.

The CrN coatings were performed on 316 L austenitic stainless steel, skh51 high speed steel, and YG8 cemented carbide using plasma-enhanced magnetron sputtering system. The adhesion and failure mechanism of the hard CrN coatings on different kinds of substrates were investigated. The morphology, microstructure, crystallinity, as well as nano-hardness and Young' modulus of the as-deposited coatings were investigated by scanning electron microscopy, X-ray diffraction, and nano-indentation testing system, respectively. In particularly, the adhesion and failure mechanism of different coating-substrate systems were evaluated by scratch and indentation tests. Apparently, the adhesion and failure mechanism of the CrN coatings were significantly influenced by the species of substrates. The results of the scratch test indicated that the increase of adhesion strength (Lc = 190 N) of the CrN coating to YG8 was associated with the formation of the obvious indented coating-substrate interface, and the higher modulus of the substrate, which provided a better load-carrying capacity, whereas the CrN coating deposited on 316 L in contrast. In Rockwell indentation test, the main failure mechanism of the CrN coatings on substrate with high modulus were mainly brittle fracture, whereas the CrN coatings deposited on soft substrate was failed in ring cracks, which was attributed to the asynchronous recovery between the substrate and the coating.

This study examines the physical characteristics of hollow cathode vacuum arcs under axial magnetic field confinement (ME-HCVA). These characteristics mainly include voltage-current response, arc shape, spectral intensity. According to the experimental results, the ME-HCVA was compressed into a blue-white column at low discharge current. As the gas flow increases, the ME-HCVA power exhibits characterized by two stages: a reduces stage (low gas flow) and a stable stage (high gas flow). The axial magnetic field increased the ME-HCVA discharge voltage indicating that the axial magnetic field can increase the ME-HCVA power. The ME-HCVA power at low discharge current can be greater than that at high discharge current by changing the gas flow rate. As the applied magnetic field increased in intensity, the spectral intensity of the ME-HCVA first increased and then stabilized. The spectral line intensity of Ar ions in the ME-HCVA (ArII) increased more rapidly than that of Ar atoms. The axial magnetic field increases the melting width, depth and depth-to-width ratios of the ME-HCVA.

The discharge and deposition characteristics of high-power impulse magnetron sputtering using various target materials with different sputtering yields (Cu, Cr, Ti, and C) were analyzed by a plasma global model. The experimental discharge voltages and currents of various target materials were used as the input parameters of the model. The analysis reveals that the ionization fraction of the sputtered species decreases as increasing the sputtering yield, due to the electron temperature was reduced through the cooling effect of sputtered species. However, as the sputtering yield increases, the plasma density under a given discharge power density is increased and the self-sputtering runaway can be fully developed, resulting in a higher fraction of ion density in the form of metal ions in the ion deposition flux. For some high-sputtering yield materials, such as Cu and Cr, this fraction can be up to 95%.

Etching of the cathodes in magnetron sputtering determines the plasma discharge properties and deposition efficiency. In high-power and high-ionization discharges, etching becomes more complicated, resulting in inaccurate results if the conventional models are still used. This work aims at establishing an accurate dynamic model for high-power and high-ionization discharges by combining the cellular automata (CA) method and particle-in-cell/Monte Carlo collision (PIC/MCC) method, in which all the interactions pertaining to the etching morphology, plasma density, electric field, and magnetic field are considered. In high-power discharges such as continuous high-power magnetron sputtering (C-HPMS), strong self-sputtering and intense gas rarefaction stemming from the high temperature in the vicinity of the target influence the etching behavior. Compared to the experimental results, the morphology simulated by the dynamic etching model shows an error of only 0.8% in C-HPMS, which is much less than that obtained by the traditional test-electron Monte Carlo (MC) method (10.1%) and static PIC/MCC method (4.0%). The dynamic etching model provides more accurate results to aid the development and industrial application of HPMS.

In order to improve the length of plasma in a whole tube and mechanical properties of Cr films deposited on the inner surface of the tube, a high-power impulse magnetron sputtering coating method with a planar cathode target and auxiliary anode was proposed. The auxiliary anode was placed near the tube tail to attract plasma into the inner part of the tube. Cr films were deposited on the inner wall of a 20# carbon steel tube with a diameter of 40 mm and length of 120 mm. The influence of auxiliary anode voltage on the discharge characteristics of the Cr target, and the structure and mechanical properties of Cr films deposited on the inner surface of the tube were explored. With higher auxiliary anode voltage, an increase in substrate current was observed, especially in the tube tail. The thickness uniformity, compactness, hardness and H/E ratios of the Cr films deposited on the inner surface of the tube increased with the increase in auxiliary anode voltage. The Cr films deposited with auxiliary anode voltage of 60 V exhibited the highest hardness of 9.6 GPa and the lowest friction coefficient of 0.68.

The coatings applied onto woodworking tools must possess higher hardness, adhesion, and fracture toughness. The CrN/CrCN multilayered coatings are deposited on M2 high-speed steel (HSS) and Si (100) by cathodic arc evaporation with different C2H2 flow rates and characterized systematically. The addition of carbon to the CrN coatings can enhance the toughness of coatings and the H/E ratio. The H/E and H3/E2 ratios reach 0.085 and 0.176, respectively. The maximum nanohardness of the coatings is 24 GPa and the smallest friction coefficient is 0.48 together with the higher adhesion between the coating and substrate (HF1). Larger C2H2 flow rate can produce porous and loose microstructure with poor mechanical properties. The lifetime of the CrN/CrCN-coated blades made of high speed steel and cemented carbide materials is increased by about 33% and 7% respectively compared to that of CrN-coated blades, and by 170% and 110% compared to that of uncoated blades.

Hydrogenated diamond like carbon (a-C:H) coatings typically have low friction but high residual stress. The hardness which depends on the sp3 proportion increases not only the coating lifetime, but also the residual stress which can lead to easy film delamination especially for thick coatings. In this work, several thick a-C:H coatings (>10 μm) with different stress and hardness are prepared using stress engineering to mitigate stress accumulation while the hardness is retained. A low compressive residual stress of 0.42–0.84 GPa is achieved from the 8 μm thick a-C:H coating in addition to a high critical load of 63–74 N and hardness of over 26 GPa. The other desirable tribological and anticorrosion properties include a small friction coefficient of 0.13, low wear rate of 1.01 × 10−15 m3/N·m, high corrosion potential of - 479.6 mV, as well as small corrosion current density of 1.77 μA/cm2.

This paper reports experimental investigation of the discharge behavior of pulse-enhanced vacuum arc evaporation (PEVAE) with titanium target. The PEVAE discharge was analyzed by optical emission spectroscopy, monitoring of substrate current and the electron probe current at different N2 pressure or arc current, respectively, compared to that of conventional dc arc. The results show that during the PEVAE process the electron probe current was significantly enhanced particularly at a higher pulsed current. An increase of up to more than 1–2 times was observed. Electron emission was substantially enhanced. The substrate current increased linearly with arc current regardless of the dc or PEVAE mode; however, the latter led to a larger current-rise slope. The substrate current with the PEVAE mode was improved to over 7 times. The optical emission spectra of plasma at nitrogen atmosphere showed that the intensities of ion species (e.g., Ti2+, Ti+, N+, N2+) gradually increased with pulsed arc current for the PEVAE mode. Electron temperature derived from Ti+ ion spectra was 0.55–0.6 eV and changed slightly in the PEVAE mode or dc mode. The increase in plasma spectral intensity is caused by the plasma density increase from larger ion density. These results imply that PEVAE may be an effective technique for film deposition of better microstructure and properties due to higher substrate current induced by larger electron emission and plasma density.

The coatings applied onto woodworking tools must possess higher hardness, adhesion, and fracture toughness. The CrN/CrCN multilayered coatings are deposited on M2 high-speed steel (HSS) and Si (100) by cathodic arc evaporation with different C2H2 flow rates and characterized systematically. The addition of carbon to the CrN coatings can enhance the toughness of coatings and the H/E ratio. The H/E and H3/E2 ratios reach 0.085 and 0.176, respectively. The maximum nanohardness of the coatings is 24 GPa and the smallest friction coefficient is 0.48 together with the higher adhesion between the coating and substrate (HF1). Larger C2H2 flow rate can produce porous and loose microstructure with poor mechanical properties. The lifetime of the CrN/CrCN-coated blades made of high speed steel and cemented carbide materials is increased by about 33% and 7% respectively compared to that of CrN-coated blades, and by 170% and 110% compared to that of uncoated blades.

The Cr-C-N coatings were deposited on M2 high-speed steel (HSS) and Si (100) wafer using conventional magnetron sputtering (CMS) and electromagnetically enhanced magnetron sputtering (EMEMS) techniques. Different external magnetic field strength was generated by varying the electromagnetic coil current from 0 to 90 A. The substrate current density (J) was measured and the microstructure and hardness of the Cr-C-N coatings was investigated by field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and micro-hardness tester. The results showed that the J increased by a factor of more than 2 with the assistance of a coil current of 90 A, indicating a significantly enhanced glow discharge. The Cr-C-N coatings showed dense columnar grain structure. All coatings exhibited a granular surface morphology with a decrease in the granular size as the coil current increased. The structural improvement was attributed to the enhanced ion bombardment from the increased ion flux generated by the EMEMS technique. By increasing the coil current above 30 A, Cr-C-N coatings exhibited smaller intensity ratio of the D-Raman peak and the G-Raman peak (ID/IG), which indicated higher sp3 contents in the coatings. The maximum microhardness (approximately HV 1560) of the coating was obtained at a coil current of 90 A.

Diamond-like carbon (DLC) coatings have attracted much attention due to their excellent hardness, low friction, and superior corrosion resistance. Unfortunately, the poor adhesion caused by internal stress limits the typical thickness to below 3–5 μm. This paper presents a novel interlayer design and interface engineering and the induced excellent adhesion of thick diamond-like carbon (DLC) coatings on a high speed steel substrate. The interlayer has fundamentally a graded Cr/CrCx/CrC/DLC structure, but various treatments to the hetero-interfaces have been conducted including sequential energetic ion bombardments with Cr at the substrate/Cr interface using high-power impulse magnetron sputtering (HiPIMS) and with C at the CrC/DLC interface using an anode layer ion source. It has been observed that the critical load has been improved from 18 N for a single Cr interlayer to 77 N for a Cr/CrCx/CrC interlayer for thick DLC coatings of 13 μm. Using the same design, a very high critical load of 73 N has been achieved on the ultra-thick DLC coating of 50 μm. This interlayer design has allowed the deposition of a DLC coating that is not only thick but also hard with excellent tribological properties. The DLC coatings have a high hardness of >18 GPa, a low friction coefficient of 0.12 and a low wear rate of (1.7 ± 0.2) × 10−15 m3/N·m. This paper discusses the effect of the ion bombardment of the interlayer on the coating adhesion and the strengthening mechanisms.

The deposition rate of ta-C films was increased by imposed pulse cathodic arc deposition (IP-CAD). The arc discharge behavior, deposition rate and micro-hardness of the ta-C films were investigated at average arc currents (Iaverage) ranging from 60 A to 100 A. The average substrate current density of IP-CAD was higher than that of DC-CAD at the same Iaverage. The optical emission spectra demonstrated that a dramatic increase in the evaporation rate of both carbon atoms and ions were achieved by imposing high pulsed current with Iaverage of 80 A. As the IAverage increased from 60 A to 100 A, the deposition rate increased by about 110% for the IP-CAD and by 33% for DC-CAD. This might be attributed to the cooperative actions of high evaporation rate of the carbon, large arc pressure near the arc spots and the focusing effect induce by high current. As compared to DC-CAD, the IP-CAD mode led to smaller concentration of sp3 (44%) than DC-CAD (59%) at the IAverage of 80 A. However, the IP-CAD ta-C films exhibited higher micro-hardness (~44.7 GPa) than that of DC-CAD (24 GPa). A preferable toughness was simultaneously obtained for IP-CAD.

By combining the advantages of the thermo-mechanical properties of TiAlN and self-lubricating properties of diamond-like carbon (DLC), a multi-layered TiAlN/DLC coating is fabricated by filtered cathodic vacuum arc and magnetron sputtering. According to the different morphology and mismatch between the physical and chemical properties of TiAlN and DLC, multiple methods are used to study the growth mechanism of crystalline TiAlN and amorphous DLC in the combined system. The morphology evolution depending on the bias is studied and the brittle interface is assessed by scratch experiments. The results show that an interlamination failure occurs at the top of first DLC layer due to the cluster morphology obtained by small bias, however, the failure moves to the interface above the substrate when the clusters are refined by increasing bias. By adopting the stepwise decreased bias, the 4.5 μm thick TiAlN/DLC multi-layer coating is fabricated and does not exhibit interfacial failure at any interface between TiAlN and DLC in the scratch experiments up to a load of 100 N. Excellent adhesion (Lc = 63 N) is also achieved from coatings deposited on high-speed steel with optimized Cr/CrCx/CrC interlayers prepared by high-power impulse magnetron sputtering.

W-Nb-N coatings with Nb content ranging from 0 to 13.2 at.% were deposited by reactive magnetron sputtering technique. The influence of Nb content on the structure and mechanical properties was investigated. The results show that Nb atoms substitute W atoms forming the solid solution W-Nb-N. All the coatings exhibit a single-phase face-centered cubic (fcc) structure and the preferred orientation changes from (200) to (111) with Nb addition. The grain size of W-Nb-N coatings decreases with the increase of Nb content. The hardness and elastic modulus of W-Nb-N coatings increase gradually from 28.0 GPa to 320 GPa at 0 at.% Nb to 36.0 GPa and 386 GP at 13.2 at.% Nb, respectively. The adhesion between coatings and Si substrate also could be improved by Nb addition.

The high power impulse magnetron plasmas (HIPIMS) were employed as a novel deposition technique, which had the benefit of providing a high ionization degree. In contrast, due to the ion return effect, the deposition rate was relatively low compared to the conventional direct current. In this paper, the external electric field and external magnetic field enhanced simultaneously the HIPIMS ((E-MF)-HIPIMS) to achieve higher deposition rate of the coatings. The vanadium coatings were deposited by the (E-MF)-HIPIMS at equivalent average target powers. The substrate peak ion current density measured in the (E-MF)-HIPIMS mode was increased by a factor of 4 to the discovered current density for the HIPIMS conditions when the anode voltage was set to 70 V. The enhanced ion flux bombardment from the highly ionized (E-MF)-HIPIMS plasma led to the formation of a smoother surface and a denser structure. At the same average target power for the vanadium coatings depositions, the (E-MF)-HIPIMS exhibited higher deposition rates compared to the conventional HIPIMS by approximately 73%. The (E-MF)-HIPIMS sputtered vanadium coating exhibited significantly higher-sized film and substrate interface bonding strengths than compared to the HIPIMS by the Rockwell adhesion testing. In addition, the (E-MF)-HIPIMS sputtered vanadium coating exhibited an improved friction coefficient and improved corrosion resistance compared to the substrate and the HIPIMS sample. The improvement occurred due to the enhanced particle ionization and intense ion bombardment.

As a newly emerging high ionization physical vapor deposition method, high power impulse magnetron sputtering (HIPIMS) has wide and promising prospects. Besides, the low efficiency of electron utilization and the ionization rate of the metallic particles still require to be further improved when utilized in practical industry applications. In the present work, a novel HIPIMS discharge mode that being enhanced synergistically by both the electric and magnetic fields were proposed. The synergistic enhancement discharge effect was investigated through a current sensor, plasma emission spectrometry, and higher electron utilization efficiency and sputtering particle ionization rates were obtained. The results demonstrated that, the application of external magnetic field significantly constrained the plasma and enhanced the uni-directionality. The target discharge current decreases remarkably under constant target pulse conditions, whereas the ion current collected by the substrates increases remarkably. This means that more ions participated in the film deposition process, and the number of absorbed ions and lost ions reduce significantly with the low electric potential and the scattering, respectively. The introduction of the external auxiliary anode changed the electric field and electric potential distribution in the discharging zone, which enhanced the discharging intensity, whereas the density and charge state of plasma in the system increased substantially. When the electric and magnetic fields are present at the same time, a synergistic enhancement effect occurs and interaction enhancement and the plasma density is significantly increased in all positions, which is approximately 5 times the conventional HIPIMS under charging.

A plasma electron source design for generating beam plasma at low gas pressures is reported. The designed plasma electron source can run stably in the pressure range between 0.1 Pa and 4 Pa. The electron source emission current increases as the working pressure increases. The DC electron beam can reach 11 A at an extraction voltage of 400 V and a gas pressure of 4.0 Pa, which is experimentally verified in this article. This low energy and high current electron beam interacts with gas molecules to generate a beam plasma, which increased the plasma electron source output current. As the working pressure and emission current increased, the beam plasma emission spectrum intensity increased.

The corrosion resistance of aluminum and its alloys requires improvement in some applications. In this work, a 20 μm thick compact alumina coating doping Fe and P is obtained on the substrate of LY12 Al alloy by combining micro-arc oxidation (MAO) and phosphating to improve the corrosion resistance. The reaction mechanism is investigated and proposed. The coating shows a relatively small surface roughness (Ra = 0.5 μm) and a high Vickers hardness (1200 HV). The corrosion resistance is evaluated by the salt spraying test and Tafel polarization and a lifetime of up to 1800 h and a passivation potential of above 10 V are observed.

Lead-free solder is widely used in the industry, especially in wave soldering. However, the stainless steel holders used in wave soldering are prone to corrosion by the lead-free solder due to increased reactive wetting. Besides, owing to the high affinity between the holders and solder, they are often used to take solder out of the container. To improve tin repellence and the mechanical properties of the stainless steel holders, Ti/TiC and Ti/TiC/DLC coatings are deposited by filtered cathodic vacuum arc (FCVA) and plasma immersion ion implantation and deposition (PIII&D). The morphology, structure, composition, microhardness, wear resistance, electrochemical properties, and wetting characteristics are investigated systematically. The DLC coating, which has an amorphous structure and I D /I G ratio of about 0.55, further enhances the frictional properties, corrosion resistance, and hydrophobic characteristics of the Ti/TiC structure. The surface-modified holders show excellent tin repellence in wave soldering.