High-power Impulse Magnetron Sputtering Technology Research Articles

Magnetron sputtered ß-Ti coatings for biomedical application: A HiPIMS approach to improve corrosion resistance and mechanical behavior

This work presents the surface modification of commercially pure Ti specimens (c.p.-Ti) prepared by conventional powder metallurgy by depositing a thin film of a ß-Ti alloy (Ti-35Nb-7Zr-5Ta, wt. %, TNZT). Two types of pulsed technologies: conventional (p-DC) and high-power impulse magnetron sputtering (HiPIMS), with and without bias assistance (−60 V) under similar power conditions (250 W) were applied on titanium specimens and silicon substrates leading to different film morphologies and functional properties. Microstructural, X-ray diffraction, nanoindentation, surface wetting, XPS and electrochemical impedance measurements were done to characterize their functionality. All the coatings presented a reduced Young’s Modulus (E ≤ 80GPa) compared to the bulk Ti, representing a reduction of more than 30 %. This decrease can significantly contribute to the reduction of the stress-shielding effect, mitigating the risk of implant loosening and failure. The hardness values of TNZT coatings, slightly lower than c.p.-Ti substrate, range from 4.1 to 4.7 GPa. XPS analysis shows a passivation layer of TiO2, Nb2O5, and ZrO2, which offers high impedance and excellent corrosion resistance. The best compromise between mechanical and corrosion properties is achieved with the HiPIMS technology, thanks to its compact film microstructure with high electrical resistance, despite its limited thickness of about 1 μm.

Insights into 1200 °C steam oxidation behavior of Cr coatings with different microstructure on Zircaloy-4 alloys for enhanced accident tolerant fuel cladding

In order to improve the 1200°C steam oxidation properties of Cr-coated zirconium alloy accident tolerant fuel cladding tubes, chromium coatings with various micro-structures were fabricated by bipolar high-power impulse magnetron sputtering technology. The microstructures of chromium coatings transforms from unconsolidated column structure to dense & column-oblate structure with the bias voltage increase. Hardness and elastic modulus values of optimal chromium coatings are approximately 19.1 GPa and 374.8 GPa, respectively, which are 2.09 and 1.60 times higher than those of chromium coatings with unconsolidated column structures. Optimal chromium coatings with dense & column-oblate structures display preferable 1200°C steam oxidation resistance because of possession lower weight gain value and thicker Cr2O3 oxide layer after 2 h exposure periods. The fabrication strategy of chromium coatings with dense & column-oblate structure is expected to pave the way for enhancing 1200 °C steam oxidation resistance for Cr-coated zirconium alloys.

Novel high-efficiency plasma nitriding process utilizing a high power impulse magnetron sputtering discharge

Lifetime and biocompatibility of orthopedic implants are crucial in meeting the new challenges brought about by the fall in the patient age and the aging population. The high-load surfaces in contact with the biological environment must display enhanced tribological properties, biocompatibility, and reduced metal ion release in long-term clinical performance. Surface modification techniques such as nitriding can significantly improve the in-service behavior of the medical-grade alloys in current use. We report on a novel approach for nitriding of CoCrMo alloys using high power impulse magnetron sputtering (HIPIMS) discharge. The new nitriding process has been successfully carried out at the National HIPIMS Technology Centre at Sheffield Hallam University, UK, in an industrial size Hauzer 1000-4 system enabled with HIPIMS technology. While the nitriding ion flux is controlled by the HIPIMS magnetron plasma source, the ion energy can be independently set via the substrate bias. Implementing the HIPIMS source allows reducing the operational pressure by one order of magnitude compared to conventional dc plasma nitriding (DCPN). Plasma analyses have identified significantly enhanced production of ions of molecular nitrogen (N2+), atomic nitrogen (N+), and N2H+ radicals in the HIPIMS discharge compared to DCPN. Because of the low pressure of operation of the HIPIMS process, the energy of ions is similar to the bias voltage, whereas the high pressures used in DCPN cause severe losses in ion energy due to scattering collisions within the sheath. The high flux and high ion energy are primarily responsible for achieving a fourfold increase in process productivity as compared to state-of-the-art plasma nitriding processes. The nitrided surface layers exhibit excellent mechanical and tribological properties, which bring about significant improvements in hardness, fracture toughness, and wear. The protective function of the nitrided layer against corrosion in the aggressive environments of simulated body fluid is remarkably augmented. The barrier properties of the nitrided layer have been demonstrated through a reduction in metal ion release by as much as a factor of 2, 4, and 10 for Co, Cr, and Mo, respectively.

Mechanical and Tribological Properties of CrCN, CrAlN, and CrAlCN Coatings Deposited on Tungsten Carbide Substrates by High-Power Impulse Magnetron Sputtering Technology

Mechanical and Tribological Properties of CrCN, CrAlN, and CrAlCN Coatings Deposited on Tungsten Carbide Substrates by High-Power Impulse Magnetron Sputtering Technology

Effect of Si contents on microstructure and mechanical characteristics of TiAlSiN thin film deposited by HiPIMS using different Ti[sbnd]Si target compositions

High Power Impulse Magnetron Sputtering (HiPIMS) PVD deposition technology offers smoother coating enhanced mechanical properties and improved substrate-coating adhesion and has become a superior alternative to direct current magnetron sputtering (DCMS). The technology utilizes high peak power with a small pulse duration, leading to a much denser plasma in the order of 1018 m−3. This results in dense, defect-free, and high-quality smoother coatings. In this study, TiAlSiN coatings were deposited on WC-10Co (wt%) cermet using HiPIMS technology with two different TiSi contents. A pair of TiSi targets, either of compositions Ti77Si23 or of Ti66Si34, were used during the depositions along with another pair of Ti40Al60, in successive cathode-stages. The impact of Ti and Si atomic percentages on the microstructure and mechanical properties of the coatings was investigated using various techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), 3D-surface profiling, nano-indentation, Rockwell indentation-adhesion, and scratch test. The coating's thickness and deposition rate were estimated from the cross-section morphology. The results suggested that the TiAlN phase likely existed in an amorphous phase of Si3N4 in TiAlSiN coatings. As the Ti atomic percentage in the layer increased, the hardness improved, reaching up to 42 GPa (max). Additionally, the coating surface roughness decreased from 14.3 nm to 10.9 nm, and the grain size decreased from 10 nm to 9 nm. The adhesion strength observed under the Rockwell-indentation test was rated as HF1 in both cases. Furthermore, the indentation test revealed similar crack patterns, but an increase in Ti content significantly improved the coating-substrate adhesion, as confirmed by the Scratch test. The scratch test demonstrated a maximum load of 173 N during the complete delamination (Lc3) of TiAlSiN from the carbide substrate.

Characteristics of high-power impulse magnetron sputtering (HiPIMS) deposited nanocomposite-TiAlSiN coating under variable pulse frequencies

In the present study, nanocomposite-TiAlSiN coatings were deposited on WC-Co blocks using HiPIMS technology by varying pulse frequency. Its immediate effect on V–I signature and subsequent results on coating characteristics was critically investigated. Both substrate and target were negatively biased in pulsed mode but the voltage pulses on substrate was set with an offset of 40 μs, with respect to those on targets to avoid gas ion entrapment within coating. Variation of elemental composition, cross-sectional morphology, surface topography, hardness, and adhesion strength of the coating deposited under different pulsed frequencies, were analyzed in depth. TiAlSiN at the highest frequency, showed significant improvements in hardness and scratch resistance. A significant rise in Lc3 was recorded to be from 137.5 to 158.5 N when the pulse frequency was increased from 1 to 4 kHz. On the other hand, the peak target current was found to decrease from 340 A to 106 A. XRD spectra of TiAlSiN showed a peak shift from AlN (200) to TiAlN (200). Higher deposition rates were achieved with higher frequency but a compromise on surface smoothness, which was measured (Sa) with an increase from 9.42 to 14.32 nm.

Tribological and mechanical properties of ZrxNy films obtained by HiPIMS in DOMS mode

Maritime transportation represents one of the biggest industries worldwide. The functionality improvement of critical ship parts such as sea chest gratings could mean substantial impacts in fuel consumption reduction, larger lifetime span or reduction of non-indigenous sea species transportation. Since 2008, the ban imposed by the international maritime organization over polluting products, especially tributyltin, created the need to explore new sustainable and environmentally friendly alternatives. Multifunctional coatings have the potential to overcome this situation, creating highly tuneable materials able to combine properties according to the naval industry's needs. Zirconium nitride is known for its reliable mechanical and anti-corrosion properties, critical in a multifunctional coating used in the sea. In the present study, this material was obtained through high-power impulse magnetron sputtering technology in a reactive atmosphere (R-HiPIMS). SEM, EDS, AFM and XRD were used to assess the coatings. Also, the films’ mechanical properties and adhesion were assessed via nanoindentation and progressive load scratch tests, respectively. The pin-on-disk test was used to assess the coatings' tribological properties under dry and wet (3.5% wt. NaCl solution) conditions. The results demonstrate that the increase in hardness was directly influenced by the changes in the structure promoted by the nitrogen rise, from 16 GPa to 25 GPa, with a nitrogen increase in film composition from 47% to 54%. Besides, the tribological tests revealed the key role of an oxygen-rich tribolayer and surface roughness features (skewness and kurtosis) in keeping the film’s integrity. The ZrxNy films obtained by HiPIMS improved the mechanical and tribological properties compared to ZrN obtained by DCMS, opening new possibilities to be explored as a solution inside a multifunctional coating system.

Mechanical and anti-corrosion behaviour of ZrNxOy films deposited by Reactive High-Power Impulse Magnetron Sputtering for maritime applications

The maritime industry is one of the most prominent players in globalisation. Corrosion, wear, and biofouling are common problems in sea-chest gratings, constantly exposed to seawater. PVD technologies could avoid these problems by supplying environmentally friendly multifunctional solutions. This work developed zirconium oxynitrides films through high-power impulse magnetron sputtering technology in a reactive atmosphere (R-HiPIMS), using two kinds of oxygen inlet flow regimes: pulsed and steady. SEM-EDS, AFM and XRD assessed the coatings' physical and structural properties. Nanoindentation and scratch tests established the mechanical properties and film adhesion. Potentiodynamic polarisation (PP) and electrochemical impedance spectroscopy (EIS) determined the corrosion resistance of the coatings using saline solution (3.5 % wt. NaCl) until 168 h of exposure. The deposition conditions promoted the featureless growth profile with high densification in the films. The oxygen pulses during deposition promoted a multilayered stack growth with poor and rich oxidised layers, which showed a mixed-phase microstructure from ZrN to ZrO2 and some intermediate phases. The film growth directly influenced the hardness in multilayered films and mixed phases in the monolithic ones. Films adhesion improved with oxygen inclusion. Corrosion tests disclosed that the film densification ruled the corrosion resistance. Implementing HiPIMS technology could contribute to achieving sea-chest gratings with higher corrosion resistance, reducing maritime industry costs.

Taguchi Optimization of Wear Resistance of CrN Coatings Deposited on WC Substrates Using High-Power Impulse Magnetron Sputtering Technology and Application to High-Speed Micro-Drilling

Taguchi Optimization of Wear Resistance of CrN Coatings Deposited on WC Substrates Using High-Power Impulse Magnetron Sputtering Technology and Application to High-Speed Micro-Drilling

Conductive polyurethane nanofiber membrane prepared through high-power impulse magnetron sputtering using brass alloy

In this work, a copper-rich α-phase brass alloy was deposited on the surface of polyurethane nanofiber membranes with different densities using high-power impulse magnetron sputtering technology. The microstructural and electrical properties of the brass-coated membranes were investigated using a cold field emission scanning electron microscope with an energy dispersive spectrometer, atomic force microscope, a multipurpose thin-film X-ray diffractometer, and low impedance meter with a four-point probe. A network analyzer with a coaxial tube was used to analyze the resistance characteristics and electromagnetic shielding effectiveness of the samples. Results indicated that the brass alloy was evenly deposited on the surface and inner layers of the nanofiber membrane. Brass nodules were stacked on the surface of nanofibers and had a granular structure. The nanofibers of all membranes were neither damaged nor degraded after deposition. The brass-coated membrane provided a good conductive path on the surface. When the deposition time increased, the deposition of brass nodules on the membrane was more complete and uniform, which reduced the surface resistance and improved the electromagnetic shielding performance of the membrane.

A Comparative Study in the Tribological Behavior of DLC Coatings Deposited by HiPIMS Technology with Positive Pulses

During the last few decades, diamond-like carbon (DLC) coatings were widely used for tribological applications, being an effective tool for improving the performance and the useful life of different machining tools. Despite its excellent properties, among which stand out a high hardness, a very low friction coefficient, and even an excellent wear resistance, one of the main drawbacks which limits its corresponding industrial applicability is the resultant adhesion in comparison with other commercially available deposition techniques. In this work, it is reported the tribological results of a scratch test, wear resistance, and nanoindentation of ta-C and WC:C DLC coatings deposited by means of a novel high-power impulse magnetron sputtering (HiPIMS) technology with “positive pulses”. The coatings were deposited on 1.2379 tool steel which is of a high interest due to its great and wide industrial applicability. Finally, experimental results showed a considerable improvement in the tribological properties such as wear resistance and adhesion of both types of DLC coatings. In addition, it was also observed that the role of doping with W enables a significant enhancement on the adhesion for extremely high critical loads in the scratch tests.

P-type cuprous oxide thin films with high conductivity deposited by high power impulse magnetron sputtering

CuxO thin films were deposited on glass and silicon substrates by High Power Impulse Magnetron Sputtering (HiPIMS) at room temperature from a metallic copper target. The influence of pulse off-time on the films’ structural, morphological and optoelectronic properties was investigated. It was found that the power intensity applied on the Cu target was strongly affected by pulse off-time, which had an important impact on the films’ composition. Upon increasing the pulse off-time from 500μs to 3500μs (pulse on-time fixed at 50μs), the films’ crystallinity as well as transmittance in the visible region both ameliorate. Meanwhile, the conductivity type changed from n-type to p-type as the films’ composition changed. When the pulse off-time was fixed at 2000μs, the optimal p-type conductivity of about 3S×cm−1 was achieved, which is the highest p-type conductivity reported for Cu2O films in the last few years. The transition of the films’ conductivity type can be utilized for the fabrication of Cu2O-based p-n homojunction, and may also prove useful in developing other oxide films by using HiPIMS technology.

Technical Note:Corrosion Behavior of Post-Deposition Polished Droplet-Embedded Arc Evaporated and Droplet-Free High Power Impulse Magnetron Sputtering/Direct Current Magnetron Sputtering Coatings

In this study, the effect of metal-rich core of the droplets on the corrosion properties of TiN, CrN, and ZrN arc evaporated nitride coatings has been investigated and the corrosion properties of such coatings have been compared with droplet-free, highly dense coatings grown by combined high power impulse magnetron sputtering (HIPIMS) and direct current magnetron sputtering (DCMS) technique. An industrial size coating deposition system enabled with HIPIMS technology was used for the deposition of combined HIPIMS/DCMS coatings. The corrosion behavior of the coatings was studied by potentiodynamic polarization test (−1 V to +1 V) using 3.5% NaCl solution. Initially, as-deposited arc evaporated coatings with an exposed surface area of 1 cm2 were subjected to corrosion. Then, the coatings were gently polished to expose the metal-rich core of the droplets. Subsequently, fresh uncorroded area of the polished coating was subjected to corrosion with previously corroded area masked. It has been found that mechanic...

Microstructure and mechanical properties of (AlTi)xN1-x films by magnetic-field-enhanced high power impulse magnetron sputtering

Compared to conventional direct current magnetron sputtering, high power impulse magnetron sputtering (HiPIMS) gives rise to higher plasma activity which can be exploited to deposit films with the preferred microstructure and higher critical load, but in practice, most of the electrons are not effectively utilized and lost to the anode (chamber wall). In order to achieve higher ion flux to substrate and denser microstructure of the films, an external magnetic field is introduced. In our HiPIMS system, a coil around the magnetron target induces larger enhancement effects, and the substrate current can be increased by a factor of 2 or more if the proper current flows through the coil to intensify and confine the glow discharge. The magnetic-field-enhanced HiPIMS technology is adopted to produce (AlTi)xN1-x films with smooth surfaces and better mechanical properties such as surface hardness and a larger coil current produces films with lower friction. The improvement is attributed to enhanced glow discharge, more nitrogen incorporation, and intense ion bombardment.

Effect of bias voltage on the microstructure and hardness of Ti-Si-N films deposited by using high-power impulse magnetron sputtering

The huge potential of High-power impulse magnetron sputtering (HIPIMS) to improve the properties of deposited coatings has been verified. In this study, Ti-Si-N coatings were deposited on Si (111), glass and cemented carbide substrates by using HIPIMS. The influences of the peak voltage, duty cycle and total gas pressure on the transient peak current of the Ti90Si10 target was investigated in detailed. The (200) diffraction intensity decreased with increasing bias voltage from -50 V to -400 V. The hardness of the Ti-Si-N coatings deposited at various bias voltages and the internal stress at different bias voltages were studied. The results indicate that HIPIMS technology can considerably improve the mechanical capacity of the Ti-Si-N coatings, possibly due to the combined protection of the increased adhesive force with the substrate and the relatively high hardness, which are caused by densification and dislocation strengthening effects.

Deposition of nanoscale multilayer CrN/NbN physical vapor deposition coatings by high power impulse magnetron sputtering

Nanoscale multilayer CrN/NbN physical vapor deposition (PVD) coatings are gaining reputation for their high corrosion and wear resistance. However, the CrN/NbN films deposited by ABS™ (arc bond sputtering) technology have some limitations such as macrodroplets, porosity, and less dense structures. The novel HIPIMS (high power impulse magnetron sputtering) technique produces macroparticle-free, highly ionized metal plasma, which brings advantages in both surface pretreatment and coating deposition stages of the PVD process. In this study, nanoscale multilayer CrN/NbN PVD coatings were pretreated and deposited with HIPIMS technology and compared with those deposited by HIPIMS-UBM (unbalanced magnetron) and by the ABS™ technique. In all cases Cr+ etching was utilized to enhance adhesion by low energy ion implantation. The coatings were deposited at 400 °C with substrate biased (Ub) at −75 V. During coating deposition, HIPIMS produced significantly high activation of nitrogen compared to the UBM as observed with mass spectroscopy. HIPIMS-deposited coatings revealed a bilayer period of 4.1 nm (total thickness: 2.9 μm) and hardness of 3025 HK0.025. TEM results revealed droplet free, denser microstructure with (200) preferred orientation for the HIPIMS coating owing to the increased ionization as compared to the more porous structure with random orientation observed in UBM coating. The dry sliding wear coefficient (Kc) of the coating was 1.8×10−15 m3 N−1 m−1, whereas the steady state coefficient of friction was 0.32. Potentiodynamic polarization tests revealed higher Ecorr values, higher pitting resistance (around potentials +400 to +600 mV), and lower corrosion current densities for HIPIMS deposited coatings as compared to the coatings deposited by ABS or HIPIMS-UBM. The corrosion behavior of the coatings qualitatively improved with the progressive use of HIPIMS from pretreatment stage to the coating deposition step.