CrN Coatings Research Articles

Effect of Pulsing Configuration and Magnetic Balance Degree on Mechanical Properties of CrN Coatings Deposited by Bipolar-HiPIMS onto Floating Substrate

Despite its great potential for thin films deposition and technological applications, the HiPIMS technology has its own limitations including the control of ion energy and flux towards the substrate when coping with the deposition of electrical insulating films and/or the deposition onto insulating/electrically grounded substrates. The bipolar-HiPIMS has been recently developed as a strategy to accelerate the plasma ions towards a growing film maintained at ground potential. In this work, the benefits of bipolar-HiPIMS deposition onto floating or nonconductive substrates are explored. The effect of bipolar-HIPIMS pulsing configuration, magnetic balance-unbalance degree, and substrate’s condition on plasma characteristics, microstructure evolution, and mechanical properties of CrN coatings was investigated. During the deposition with a balanced magnetron configuration, a significant ion bombardment effect was detected when short negative pulses and relative long positive pulses were used. XRD analysis and AFM observations revealed significant microstructural changes by increasing the positive pulse duration, which results in an increase in hardness from 7.3 to 16.2 GPa, during deposition on grounded substrates, and from 4.9 to 9.4 GPa during the deposition on floating substrates. The discrepancies between the hardness values of the films deposited on floating substrates and those of the films deposited on grounded substrates become smaller/larger when a type I/type II unbalanced magnetron configuration is used. Their hardness ratio was found to be 0.887, in the first case, and 0.393, in the second one. Advanced application-tailored coatings can be deposited onto floating substrates by using the bipolar-HiPIMS technology if short negative pulses, relative long positive pulses together with type I unbalanced magnetron are concomitantly used.

Enhancing Electrical Conductivity and Corrosion Resistance of CrN Coating by Pt Addition

Transition-metal nitride coating used to protect the electronic connector devices in marine environment is required to have high electrical conductivity and good corrosion resistance. This study synthesized a novel CrN–Pt coating with a dense growth texture. Pt addition induced a pronounced increase in electrical conductivity and corrosion resistance. The resistivity decreased from 0.0149 Ohm·cm in the CrN coating to 0.000472 Ohm·cm in the CrN–Pt coating, while the corrosion current density decreased from 24 nA/cm2 in the CrN coating to 6.3 nA/cm2 in the CrN–Pt coating. The results of the above studies confirm that Pt doping has significant advantages in improving the electrical conductivity and corrosion resistance of nitride coatings for potential applications in the marine environment.

Effect of Ag content on friction and wear properties of Ag and V co-doped CrN coatings at 25–700 °C

Since the lubrication and wear resistance of important sliding parts are related to the safe operation of the whole system, it is urgent to improve the friction and wear performance of sliding parts in a wide temperature range. On this basis, Ag and V co-doped CrN coatings with varied amounts of Ag were deposited onto silicon wafers and Inconel 718 sheets by unbalanced magnetron sputtering technology. The morphology and elemental composition of the coatings were measured by Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. And the mechanical properties were assessed utilizing scratch tester and nanoindentation. The increase of silver content reduces the mechanical properties of the coating. Excessive Ag not only reduces the hardness and elastic modulus of the Ag and V co-doped CrN coating but also reduces the adhesion between the coating and the substrate. Furthermore, the friction and wear properties of the coatings against Al2O3 balls in a wide temperature (25 °C–700 °C) range were tested by a high-temperature tribometer. CrVN/Ag-0.5A coatings show the lowest wear volume at all temperatures and the lowest friction coefficient at high temperatures. Post-wear testing Raman spectroscopy measurement showed the tribo-chemical products formed on the surface of the coating effectively reduce the coefficient of friction.

Influence of plasma nitriding pre‐treatment on the corrosion and tribocorrosion behaviours of PVD CrN, TiN and AlTiN coated AISI 4140 steel in seawater

AbstractCrN, TiN and AlTiN coatings were applied by the Physical Vapour Deposition (PVD) method on AISI 4140 and plasma nitrided (PN) AISI 4140 steel. The study aimed to investigate the effect of plasma nitriding before PVD on the corrosion and tribocorrosion behaviour of AISI 4140 steel in seawater. The electrochemical corrosion behaviour of the samples was evaluated in natural seawater by the potentiodynamic polarisation method. Tribocorrosion tests were performed against alumina in natural seawater under 5 N load and open circuit potential (OCP) using a ball‐on‐disk tribometer coupled with an electrochemical cell. As a result of the study, plasma nitriding applied before the coating significantly improved corrosion and tribocorrosion resistance of PVD CrN, TiN and AlTiN coatings. Besides, it was concluded that duplex treated low alloy AISI 4140 steel could be a candidate instead of stainless steel in tribocorrosion conditions for the marine environment.

Experimental Analysis of the Influence of the Application of TiN, TiAlN, CrN and DLC1 Coatings on the Friction Losses in an Aviation Internal Combustion Engine Intended for the Propulsion of Ultralight Aircraft

Currently, there are many methods of reducing the friction losses of the main components of an internal combustion piston engine. The operating conditions of internal combustion piston engines intended for the propulsion of ultralight aircraft differ significantly from those prevailing in the case of using these engines for the propulsion of vehicles. There are many studies on the influence of selected anti-wear coatings on the friction coefficients when using various lubricants, measured via tribometers. Unfortunately, the conditions obtained in the laboratory significantly differ from those prevailing in an engine operating under external conditions. The study investigated the influence of a change in the tribological parameters of TiN, TiAlN, CrN and DLC1 anti-wear coatings on the moment of resistance to the piston movement of an aircraft engine. The operating parameters of a real engine working in an aircraft were simulated. The main focus was on the coating layers of the sliding surfaces of the piston rings and the cylinder running surface. The properties of the coatings affect the correlation of the scale of the adhesion and cohesion phenomena of the oil to the opposite planes, and this determines the nature of the changes in the moment of resistance to engine motion. As it is commonly known, with an increase in the value of the maximum pressure of the working medium in the combustion chamber, the share of mixed friction in liquid friction increases, similar to the high oil temperatures occurring in aircraft engines. Therefore, there is a justified need to supplement the research in the field of analyzing the characteristics of the torque of resistance to motion for these engines, in particular in the field of the usable rotational speeds of the crankshaft. Applicable anti-wear systems based on selected coatings can significantly improve operational safety and noticeably reduce fuel consumption.

The Effect of Al and Ti Transition Metals on the Wear Resistance of Ceramic Based CrN Coatings; Investigation under Ambient Air and Vacuum Conditions

In the present study, CrN, CrAlN and CrAlTiN coatings were deposited using the cathodic arc evaporation technique. The structural investigations of these CrN based coatings were performed by scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, X-ray diffractometer. The hardness and adhesion strength values of coatings were determined via Vickers type microhardness tester and progressive load scratch tester, respectively. The wear performance of samples was established at ambient air and vacuum condition. All coatings grew in the “T zone” growth model and had a dense and columnar structure. The XRD patterns presented predominantly (220), (110), and (111) reflections. It was demonstrated that the quaternary coating had a higher texture parameter as 0.68, which was related to the highest thickness and hardness. Also, CrAlTiN coatings with the smallest mean crystallite size of ∼87 nm showed the best hardness, and this ensured relatively high scratch resistance. CrN and CrAlTiN coatings improved wear performance under ambient air condition but were not striking as under vacuum condition. The quaternary coating had a superior performance in the vacuum condition, but due to the high sensitivity of Ti to oxygen, it fell behind the CrN coating under ambient air condition.

Hard and tough CrN coatings strengthened by high-density distorted coherent grain boundaries

Coherent grain boundaries (CGBs) has been revealed to improve the hardness and toughness simultaneously, but the density are not enough to increase their mechanical properties. Herein, hetero-interfaces are formed by introducing ion bombardment during magnetron sputtering to increase the amount of CGBs in the CrN coatings. By optimizing the sub-layer thickness, the quantity and width of CGBs from the (111) to (200) orientations increase significantly and consequently, the hardness and toughness of the CrN coating increase to 33.4 GPa and 14.98 MPa m1/2, respectively. At last, the effect of the different CGBs to the coating strengthen is discussed.

Structural, surface electronic bonding, optical, and mechanical features of sputtering deposited CrNiN coatings with Si and Al additives

Herein, the closed field unbalanced magnetron sputtered CrNiN, CrNiSiN, and CrNiAlN coatings are studied to gain insights into their structural, morphological, optical, and mechanical properties. Detailed characterizations of the thin films have been carried out through X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible–near infrared (UV–Vis) spectroscopy, nanoindentation, finite element modeling (FEM), and water contact angle measurements. XRD confirmed the hexagonal close-packed hcp-Cr2N (211) phase and face-centered cubic fcc-CrN (200) phase. The SEM images confirmed the compact, dense, and uniform distribution of gains in the coating structures. The average crystallite size of CrNiN coatings was 515 nm. The addition of substituents (Si and Al) to the CrNiN coatings resulted in increasing the crystallite sizes to 605 nm (for CrNiSiN) and 811 nm (for CrNiAlN) as well as grain size from 1.32 to 2.335 μm. XPS analysis was conducted to estimate the atomic constituents and measure the high-resolution XPS spectra of Ni2p photoelectron lines. The elastic modulus and hardness of the coatings are between 361 and 459 GPa, and 23.1–26.8 GPa, respectively. The Si, and Al additions enhanced both Young's modulus and the hardness of the coatings. Results of FEM modeling demonstrated the stress distribution within the coatings on steel and silicon substrates at different film thicknesses. The maximum stress level was increased by 30% at the coatings' upper portion, while that of the interface was reduced by 60%. The water contact angle values lay within the range of 102.4°–112.4°.

Controlling preferential growth of chromium – Nitrogen R-HiPIMS and R-DCMS films by substrate magnetic biasing

The effect of magnetic biasing on the structure of Cr-N coatings deposited on silicon substrates by reactive magnetron sputtering has been investigated. The magnetic biasing setup consisted of a permanent magnet placed close to the substrate holder to modify the plasma species dynamics and deposition flux. Three magnetic field configurations for reactive direct current magnetron sputtering (R-DCMS) and reactive High Power Impulse Magnetron Sputtering (R-HiPIMS) were compared. Deposition parameters such as deposition time, gun power, substrate distance, temperature, gas pressure, and gas composition were constant through the six R-DCMS/HiPIMS-magnetic-field combinations. Processes were monitored through optical emission spectroscopy (OES) and closely compared to the voltage and current curves at the target/substrate. An excitation mechanism was proposed accounting for the enhanced ionization detected by OES and the implications in the film’s growth. The films’ stoichiometry, structure, thickness, morphology, and crystal texture were characterized and associated with the process parameters. The R-DCMS processes led to Cr-N solid solution films, while the enhanced reactivity of R-HiPIMS plasma species increased the N content and formed CrN. Overall, the R-DCMS deposited samples were thicker than the R-HiPIMS deposited samples, but the different magnetic field biasing setups allowed for specific control of films’ thickness, texture, and microstructure.

Radioactivation Monitoring of the Density of Wear-Resistant AlN and CrN Coatings on Silicon

Radioactivation Monitoring of the Density of Wear-Resistant AlN and CrN Coatings on Silicon

Synthesis and electrochemical properties of nanoporous CrN thin film electrodes for supercapacitor applications

Transition metal nitrides (TMN) have received widespread consideration as supercapacitor materials for a variety of energy storage applications. An important requirement to such electrode materials is a very high specific surface area, which is typically obtained through a percolating pore-network. Here, we use arc ion plating to prepare CrN-Ni composite coatings with 0, 30.4, 54.2, and 77.6 at.% Ni. Detailed X-ray diffraction and X-ray photoelectron spectroscopy showed that the coatings consist of CrN phases next to metallic Ni. Post-deposition treatments with HCl solutions lead to selective leaching, causing a porous nanostructure for the Ni-containing CrN coatings. From there, the coating with 54.2 at.% Ni in its as-deposited state provided the highest (electrode-geometric-area)-specific capacitance after the HCl treatment, giving 58.5 mF·cm−2 at 1.0 mA·cm−2 in a 0.5 M H2SO4 aqueous electrolyte. This value is about 80 times higher than for the as-deposited coatings or the Ni-free CrN. Consequently, our strategy to combine TMNs with metallic Ni and its subsequent treatment with HCl is highly effective in enlarging the specific surface area and adsorption sites. It allows to significantly enhance the energy storage performance of TMN thin film supercapacitors.

WITHDRAWN: Microstructure and Properties of CrN Coating via Multi-arc Ion Plating on Valve Seat Material Surface

WITHDRAWN: Microstructure and Properties of CrN Coating via Multi-arc Ion Plating on Valve Seat Material Surface

Metallic Material Selection and Prospective Surface Treatments for Proton Exchange Membrane Fuel Cell Bipolar Plates-A Review.

The aim of this review is to summarize the possibilities of replacing graphite bipolar plates in fuel-cells. The review is mostly focused on metallic bipolar plates, which benefit from many properties required for fuel cells, viz. good mechanical properties, thermal and electrical conductivity, availability, and others. The main disadvantage of metals is that their corrosion resistance in the fuel-cell environment originates from the formation of a passive layer, which significantly increases interfacial contact resistance. Suitable coating systems prepared by a proper deposition method are eventually able to compensate for this disadvantage and make the replacement of graphite bipolar plates possible. This review compares coatings, materials, and deposition methods based on electrochemical measurements and contact resistance properties with respect to achieving appropriate parameters established by the DOE as objectives for 2020. An extraordinary number of studies have been performed, but only a minority of them provided promising results. One of these is the nanocrystalline β-Nb2N coating on AISI 430, prepared by the disproportionation reaction of Nb(IV) in molten salt, which satisfied the DOE 2020 objectives in terms of corrosion resistance and interfacial contact resistance. From other studies, TiN, CrN, NbC, TiC, or amorphous carbon-based coatings seem to be promising. This paper is novel in extracting important aspects for future studies and methods for testing the properties of metallic materials and factors affecting monitoring characteristics and parameters.

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

REACH regulation challenge: Development of alternative coatings to hexavalent chromium for minting applications

Aiming to improve the protection of human health and the environment, REACH regulation was enforced across European Union, accelerating the need to find alternative solutions to the electrodeposition processes of hexavalent chromium employed in several industrial applications. Electroplated chromium coatings are widely used due to their physical and mechanical properties that allow a longer service life of products that usually fail due to wear. Minting is one of those applications where good mechanical and tribological properties are required and where hard chromium has an important usage without being outmatched by other coatings. This study presents the development of an alternative coating to hard chromium with outstanding mechanical properties, in particular high resistance to cyclic loads . Cr( Al , Si )N coatings have been produced by reactive DC magnetron sputtering . Focusing on mechanical properties, an increase in the hardness was observed with the consecutive addition of elements to the base matrix (CrN), ranging from ≈10 GPa in CrN coatings up to ≈17 GPa for the CrAlSiN coatings. In nano-impact tests, CrAlN coatings had the best performance and no crack events by fatigue were observed by SEM after 50 impacts, with load maximum 20mN, with an estimated maximum contact pressure of 1.5 GPa much higher than the one requested for coinage. The fatigue wear was governed by the H/E ratio and plasticity index showing that Cr( Al , Si )N coatings deposited by reactive magnetron sputtering can be considered excellent candidates for cyclic loading, as in minting applications. • In nano-impact tests, CrAlN coatings withstood 1.5 GPa without failure. • Depth of initial indentation after 50 impacts was lower in CrAlN than in steel. • Cr( Al , Si )N coatings are viable alternatives to hard chromium under cyclic loads.

Effect of MoS2 content on friction and wear properties of Mo and S co-doped CrN coatings at 25–600 °C

With increasingly harsh working environments for mechanical systems and the rapid development of various high-tech industries, requirements for the stable operation of mechanical systems are increasing in a wide temperature range. Mo and S co-doped CrN coatings with different MoS2 contents were prepared via unbalanced magnetron sputtering to provide better friction properties to the coatings at high temperatures. Scanning electron microscopy and nanoindentation were adopted to analyze the microstructure and mechanical performance. The mechanical performance of the coatings was enhanced by increasing the MoS2 content, however, excessive MoS2 reduced the mechanical properties of the coatings. Besides, the adhesion of the coatings first increased and then decreased rapidly with the increase of the MoS2 content. In addition, the residual stress of the coating first decreased and then increased upon increasing the MoS2 content. The high-temperature tribological behavior of the coatings was measured from room temperature (25 °C) to 600 °C. The CrN/MoS2-0.6A coating was found to exhibit low friction and wear coefficient at room temperature and relatively good comprehensive properties at high temperature. This study provides a feasible design for engineering applications and lays the foundations for the preparation of coatings with superior high-temperature friction properties.

Application of a transmission line model to evaluate the influence of structural defects on the corrosion behavior of arc-PVD CrN coatings

The effect of bias voltages (40 V, 80 V, and 40/60/80 V) on microstructure and electrochemical properties of arc-PVD CrN coatings were evaluated. Increasing the bias voltage produced microstructural changes, from well-defined columns to columnar grains, and increased defect size. The electrochemical response proved susceptible to the defect type. Nano-droplets promoted the formation of oxides, while large pores allowed the migration of the electrolyte to the substrate/CrN interface. An impedance equivalent circuit based on the Bisquert transmission line was proposed to fit the experimentally obtained impedance spectra. The equivalent circuit allowed correlating the coating electrochemical response to the defect densities and sizes. Samples deposited with 40 V showed the lowest corrosion current (0.05 μA/cm2 ± 0.01), which was supported by the highest resistances to the transport of ions through the pores (Rp = 1047 ± 88 kΩꞏcm2). Films obtained with 80 V reduced Rp values by two magnitude orders compared to CrN 40 V. The increase of pore resistance in CrN 40 V was associated with the oxidation of nano-droplets (proposed auto-protection phenomenon), which blocks open pinholes due to the smallest average size of defects. Tailoring a gradual increase of the bias voltage (40/60/80 V) preserves the auto-protection mechanism of droplets and improves the surface finish of the coating.

Oxidation behavior, thermal stability, and the coating/substrate interface evolution of CrN-coated Zircaloy under high-temperature steam

CrN-coated Zircaloy samples were prepared by cathodic arc ion plating, and the microstructure, stability, and oxidation behaviors of the CrN coatings in high-temperature steams were comprehensively investigated. The CrN coating significantly increased the oxidation resistance of Zircaloy exposed to steam through the formation of a dense Cr2O3 oxide layer without cracking or spallation. Two different multi-layered coatings were produced after the steam exposures. The nitrogen diffusion properties of the CrN coatings during oxidation were examined. The internal oxidation of Zr particles inside the nitride coating was observed. A ZrN nano-twinned layer formed at the coating/substrate interface.

Effects of ion irradiation on Cr, CrN, and TiAlCrN coated Zircaloy-4 for accident tolerant fuel claddings

Heavy ion (6 MeV Au+) irradiation studies were carried out on three candidate coatings (Cr, CrN, TiAlCrN) and Zircaloy-4 for accident tolerant fuel cladding to investigate the irradiation resistance and microstructure evolution at 400 °C. Transmission Electron Microscopy (TEM) results showed that the irradiation defects were significantly restricted by grain boundaries in the columnar grains compared to equiaxed grains and the high-density boundaries could obviously reduce the formation of voids. Fast Fourier Transformation (FFT) results of high-resolution TEM images showed that Cr and CrN coatings maintained better lattice integrity than those of TiAlCrN coating and Zircaloy-4. ATF coatings showed less irradiation defects than that of Zircaloy-4 substrate. Cr coating exhibited better irradiation resistance than that of TiAlCrN coating in terms of irradiation dislocation loops. CrN coating showed the best irradiation resistance among all samples, due to its compact crystal structure and higher density of grain boundary, which contributed to reduce dislocations and voids.

Influence of oxygen addition on the structure, mechanical and thermal properties of CrN coating

In this study, the effect of oxygen addition on the structure, mechanical and thermal properties of CrN coatings was investigated. CrN, Cr0.50O0.07N0.43 and Cr0.47O0.22N0.31 coatings reveal a single-phase cubic structure, and further increasing oxygen content results in the formation of a corundum structured Cr2O3 coating. An increased hardness from ~16.9 GPa for CrN to ~21.9 GPa for Cr0.50O0.07N0.43, ~27.0 GPa for Cr0.47O0.22N0.31, and finally ~28.6 GPa for α-Cr2O3 is obtained. Cr0.50O0.07N0.43 and Cr0.47O0.22N0.31 coatings show a deferred onset temperature of nitrogen loss than CrN by ~100 °C. During annealing, the hardness value of the CrN coating decreases to ~11.3 GPa at 900 °C and then inversely increases to ~17.9 GPa at 1200 °C, while those of Cr0.50O0.07N0.43 and Cr0.47O0.22N0.31 coatings exhibit a continuous drop to ~14.5 and ~20.6 GPa at 1200 °C, respectively. The oxidation resistance of Cr-O-N coating is closely related to oxygen content. After oxidation at 800 °C for 20 h, the oxide scales of CrN, Cr0.50O0.07N0.43 and Cr0.47O0.22N0.31 coatings are ~0.22, ~0.16 and ~0.55 μm in thickness, respectively. In addition, the Cr2O3 coating always retains excellent mechanical and thermal properties regardless of in Ar or synthetic air.