Arc Physical Vapor Deposition Research Articles

Ceramic coating for corrosion (c3) resistance of nuclear fuel cladding

In an attempt to develop a nuclear fuel cladding that is more tolerant to loss-of-coolant-accidents (LOCA), ceramic coatings were deposited onto a ZIRLO™11ZIRLO is a trademark of Westinghouse Electric Co. substrate by cathodic arc physical vapor deposition (CA-PVD). The coatings consisted of either Ti1–xAlxN or TiN ceramic monolithic layers with a titanium bond coating layer as the interlayer between the ceramic coating and the ZIRLO™ substrate to improve coating adhesion. Several coating deposition trials were performed investigating the effects of bond coating thickness (200–800nm), ceramic coating thickness (4, 8 and 12μm), substrate surface roughness prior to deposition, and select coating deposition processing parameters, such as nitrogen partial pressure and substrate bias, in order to optimize the coating durability in a corrosion environment. Corrosion tests were performed in static pure water at 360°C and saturation pressure (18.7MPa) for 3days. The optimized nitride-based ceramic coatings survived the autoclave test exposure showing very low weight gain of 1–5mg/dm2 compared to the uncoated ZIRLO™ samples which showed an average weight gain of 14.4mg/dm2. Post-corrosion exposure analytical characterization showed that aluminum depletion occurred in the TiAlN coated samples during the autoclave corrosion test, which led to the formation of the boehmite phase that degraded the corrosion durability of some of the TiAlN samples. However, by eliminating the aluminum content and depositing TiN, the boehmite phase was prevented from forming. Best results in TiAlN coated samples were obtained with 600nm Ti bond coating thickness, 12µm coating thickness and 0.25µm substrate surface roughness (E14). Results are discussed in terms of the capability of TiN and Ti1–xAlxN coatings to improve the high temperature corrosion resistance and oxidation resistance of zirconium alloy cladding.

Effect of periodicity on hardness and scratch resistance of CrN/NbN nanoscale multilayer coating deposited by cathodic arc technique

Nano-scaled multilayer CrN/NbN coatings were produced in an industrial-size cathodic arc physical vapor deposition (PVD) chamber, with three cathodes in alternate positions (Cr/Nb/Cr). Four multilayer NbN/CrN coatings were produced with different periodicities (20nm, 10nm, 7.5nm and 4nm) with total thickness from 25 to 30μm in all cases. The coatings were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM), which provided the lattice parameter in each of the constituent layers and structural analysis of the multilayers, respectively. The multilayer coating system is composed of CrN and NbN with similar structures, but with a lattice mismatch, which varies the fraction of the region with lattice strain depending on the periodicity. For the thicker individual layers, the adjustment of lattice parameter at the interfaces does not represent a predominant fraction of the entire structure, i.e. separate peaks of NbN and CrN can be distinguished in the XRD analysis. In the presence of low periodicity (lower than 10nm), the lattice of each constituent may be coherently strained and just one intermediate lattice (d-spacing) is detected for the NbN/CrN multilayer. Mechanical and tribological characterization was conducted by microhardness measurements using a 500mN load (Instrumented indentation) and scratch tests using a conical diamond indenter with a 0.1mm tip radius. From high to low periodicity, the multilayer NbN/CrN coatings showed increasing hardness, decreasing coefficient of friction and increasing resistance to cohesive failure, possibly due to a strong (200) texture for the coatings with 10nm periodicity or less, indicating a potential better performance of the lower periodicity multilayer coating systems in service.

Effects of DLC coating on relaxing surface residual stress of the weld in titanium-bearing high-strength steel

The distribution of as-welded residual stresses in titanium-bearing low-carbon high-strength steel exhibiting two controlled initial plate temperatures (7 and 25 °C) was measured and calculated under the same heat input. The as-welded plate containing the cooling system at 7 °C exhibited a higher residual tensile stress than the as-welded plate did at room temperature (25 °C) because of the greater temperature gradient in the 7 °C system. The diamond-like carbon (DLC) thin-film coating was examined after welding and confirmed using the Raman spectrum. The successful DLC thin-film deposited on the as-welded plates further reduced and relaxed the magnitude of the surface residual stress of weld caused by the cathodic arc physical vapor deposition process. The distributions of the measured surface residual stresses on weld correspond with the finite element method simulated results.

Nanostructuring and property modification of arc PVD TiN coatings by nickel

We have studied structure and phase formation processes in the Ti-N-Ni system during the growth of coatings by cathodic arc physical vapor deposition (PVD). The incorporation of nickel has been shown to reduce the crystallite size of TiN from 100–120 to 15–18 nm. This is accompanied by a transition from a columnar microstructure, typical of PVD TiN coatings, to an equiaxed one. In the concentration range 0 to 12–13 at %, the nickel in the coatings is X-ray amorphous. Further increasing the nickel content leads to the formation of the intermetallic phase TiNi, which is in turn accompanied by the generation of pores in the structure of the coating. We have determined optimal nickel concentrations in the composite coatings (8–12 at %) that ensure hardness, Young’s modulus, H3/E2, and H/E of 52 GPa, 516 GPa, 0.57 GPa, and 0.104, respectively. We have demonstrated that the nanostructured TiN-Ni (2.8 to 12 at % Ni) coatings undergo failure by a cohesion mechanism. Complete wear of the coatings only occurred starting at a load of 90 N, attesting to high adhesion/cohesion strength of the system.

Behavior of mammalian cells on magnesium substituted bare and hydroxyapatite deposited (Ti,Mg)N coatings

TiN and (Ti,Mg)N thin film coatings were deposited on titanium substrates by using cathodic arc physical vapor deposition (arc-PVD) technique with magnesium contents of 0, 4.24 at% (low Mg) and 10.42 at% (high Mg). The presence of magnesium on both normal (hFOB) and cancer (SaOS-2) osteoblast cell behavior was investigated in (Ti,Mg)N surfaces with or without prior hydroxyapatite (HA) deposition (in simulated body fluid, SBF). Mg incorporation on TiN films was found to have no apparent effect on the cell proliferation in bare surfaces but cell spreading was better on low Mg content surface for hFOB cells. SaOS-2 cells, on the other hand, showed an increased extra cellular matrix (ECM) deposition on low Mg surfaces but ECM deposition almost disappeared when Mg content was increased above 10 at%. HA deposited surfaces with high Mg content was shown to cause a significant decrease in cell viability. While the cells were flattened, elongated and spread over the surface in contact with each other via cellular extensions on unmodified and low Mg doped surfaces, unhealthy morphologies of cells with round shape with a limited number of extended arms was visualized on high Mg containing samples. In summary, Mg incorporation into the TiN coatings by arc-PVD technique and successive HA deposition led to promising cell responses on low Mg content surfaces for a better osteointegration performance.

Performance Metrics and Experimental Testing of Erosion-Resistant Compressor Blade Coatings

A durability test rig for erosion-resistant gas turbine engine compressor blade coatings was designed and commissioned. Bare and coated 17-4PH steel modified NACA 6505-profile blades were spun at an average speed of 10,860 rpm and exposed to garnet sand-laden air for 5 h at an average sand concentration of 2.5 g/(m3 of air) and a blade leading edge (LE) Mach number of 0.50. The rig was designed to represent a first stage axial compressor. Two 16 μm-thick coatings were tested: Titanium nitride (TiN) and chromium–aluminum–titanium nitride (CrAlTiN), both applied using an arc physical vapor deposition (PVD) technique. A composite scale, defined as the Leithead-Allan-Zhao (LAZ) score, was devised to compare the durability performance of bare and coated blades based on mass-loss and blade dimension changes. The bare blades' LAZ score was set as a benchmark of 1.00, with the TiN-coated and CrAlTiN-coated blades obtaining respective scores of 0.69 and 0.41. A lower score identified a more erosion-resistant coating. Major locations of blade wear included: trailing edge (TE), LE, and rear suction surface (SS). TE thickness was reduced, the LE became blunt, and the rear SS was scrubbed by overtip and recirculation zone vortices. The erosion effects of secondary flows were found to be significant. Erosion damage due to reflected particles was absent due to a low blade solidity of 0.7. The rig is best suited for durability evaluation of erosion-resistant coatings after (AF) being proven worthy of consideration for gas turbine engines through ASTM standardized testing.

Tribological improvement of titanium alloy surfaces through texturing and TiAlN coating

Titanium alloys are characterised by poor wear resistance properties and its utilisation has been excessive in non-tribological applications. Surface texturing is a renowned and effective means of surface modification technique to improve the tribological properties of sliding surfaces. In the present work, modification of titanium alloy surfaces was done by lapping and laser surface texturing. The modified surfaces were coated by titanium aluminium nitride (TiAlN) nanocomposite coating with chromium as interlayer by cathodic arc physical vapour deposition system. The adhesion characteristics of the coatings were evaluated using a scratch tester and recognised that coating adherence has been improved by 8% through texturing. The effect of normal load on friction and wear characteristics were examined and discussed. The present work is aimed for investigating the bonding strength, friction coefficient and wear behaviour of bilayer composite coating over modified titanium alloy substrates under dry sliding contact condition.

Hydrogen gas sensing properties of nanoporous Al-doped titania

Nanoporous aluminum doped titanium (TiAl) oxide thin film sensor materials with an Al concentration of 9–10at.% were produced on alumina substrates and their hydrogen (H2) sensing behaviors were investigated. The well-adherent and dense metallic TiAl thin films with equiaxed structure were deposited on alumina substrates using cathodic arc physical vapor deposition (CAPVD) method and the nanopores were grown on the TiAl thin films by anodic oxidation in ammonium fluoride (NH4F) containing ethylene glycol (EG) electrolyte. With the deposition method utilized, it became possible to anodize the films without spalling and defects. The metallic film on alumina was totally anodized in order to eliminate short-circuit problems between the metallic layer below the oxide and Pt pads used for resistance measurements. The amorphous nanoporous structures were converted into anatase by heat treatment at 480°C for 3h and the fabrication of sensor was completed by depositing Pt contact pads on the surface of nanopores using magnetron sputtering technique. The hydrogen sensing performance of thin film nanoporous TiAl oxide sensor was studied in the range of 50–2500ppm hydrogen at different temperatures (25–350°C). The sensor characteristics in terms of sensitivity, response, recovery and stability were examined in detailed analysis and a possible hydrogen detection mechanism was proposed. The nanoporous TiAl oxide sensor exhibited promising sensing performance towards H2 gas concentrations and quick response and recovery behavior with high stability.

Electromagnetic absorbance properties of a textile material coated using filtered arc-physical vapor deposition method

We explore the structure of a textile absorber in terms of its electromagnetic and absorption properties in the microwave region. Its absorption characteristics are similar to those reported for various metamaterial-based absorbers, exhibiting absorption as high as 98% at resonance. In addition, the angular behavior of the absorption properties of the sample reveal incident angle independency, which is the other added value of the study. Also, the suggested textile absorber has a simple configuration, which introduces flexibility to adjust its material properties and easily tune its structure to suit other frequencies. The proposed textile absorber and its variations have myriad potential applications in radar technology, long distance radio telecommunication, and so on. Although in its current state the proposed structure provides almost perfect absorption covering a wide range of microwave C-Band, the developing technology will soon allow manufacturing textiles that can manipulate lights, leading to the design of invisibility cloak and other science fiction devices besides finding important application areas in medical science.

Study of Interlayer Element Effect on Properties of AlCrTiSiN Thin Film

In this work, the effect of different interlayer elements on the properties of the top AlCrTiSiN film, i.e. titanium and chromium called as Ti/AlCrTiSiN and Cr/AlCrTiSiN, respectively, was studied. The film was deposited by cathodic arc physical vapor deposition on tungsten carbide (WC) specimen which is extensively used as cutting tools material. Various properties including the surface hardness, the scratch resistance and tribological performance were later studied. The surface hardness of both Ti/AlCrTiSiN and Cr/AlCrTiSiN coatings were higher than 29 GPa. The critical load for both coating suggesting supurb adhesion strength of the coating system. However, Ti interlayer was found to result in higher critical compressive stress for first damage and full delamination at room temperature. The wear resistance of coated specimens was far better than the uncoated one both at room temperature and high temperature, i.e. ball on disc tests at room temperature, 300 °C, and 500 °C were performed. The coeeficient of friciton of both coatings were found to depend strongly on the wear behavior of the system and the characters of the wear debris. A sign of better tribological performance at high temperature, i.e. 500°C, could be noticed with Cr interlayer as the lower mismatch in coefficient of thermal expansion became more crucial in film damage phenomina at such temperature.

Increasing Tool Life by AlCrTiSiN Film

A cemented carbide end mill was coated with AlCrTiSiN film by cathodic arc physical vapor deposition methods (CAPVD). A performance of AlCrTiSiN film for increasing tool life was evaluated by scratch test, cutting test and oxidation test in comparison with uncoated end mill. From the scratch test, the AlCrTiSiN film was helpful to resist crack and delamination of coating. From the cutting test, the maximum flank wear of AlCrTiSiN film was about two times higher than that of the uncoated end mill resulting in tool life extension. From the oxidation test, the first oxide of AlCrTiSiN film generated after service life was a titanium dioxide (TiO2) at a temperature of 900oC. From all of results, it revealed that the AlCrTiSiN film significantly enhanced the tool life of the cemented carbide end mill.

Functional multi-layer nitride coatings for high temperature solar selective applications

A solar-selective functional multi-layered coating for high temperature applications has been developed on copper and stainless steel substrates using an industrially viable cathodic arc physical vapor deposition technique. The selective coating was formulated in such a way that the constituent functional layers are mainly high temperature stable nitride materials which are also hard and capable of imparting protection against wear. A multi-layer structure comprising TiAlCrN as IR reflector, TiAlN as absorber and AlSiN as anti-reflective layer was found to exhibit promising results. The stacking of these three materials with appropriate thickness in a systematic manner, viz. Cu/TiAlCrN/TiAlN/AlSiN with high Cr and Al contents in TiAlCrN and TiAlN layers, respectively, yielded high absorptivity (αAM1.5=0.91) and low emissivity (ε=0.07) values corresponding to an attractive optical selectivity (α/ε) of 13. The open air high temperature performance of the optimized multi-layer structure was also investigated in the temperature range 27–700°C and the stability of the coatings at high temperatures with respect to optical properties was established.

A Comparative Study of Wear and Oxidation Behaviors of End Mill Coated by PVD Coatings

The objective of this research is to study wear behaviors of TiN, nanolaminated AlCrN and nanocomposite TiAlSiN coated on cemented carbide end mill deposited by cathodic arc physical vapor deposition methods in comparison with uncoated end mill. Wear behaviors were investigated by nanoindentation hardness test, scratch test and cutting test. Oxidation test was also done in air at temperatures of 700°- 900°C in order to evaluate resistance of oxidation. In the nanoindentation hardness and scratch tests, nanocomposite TiAlSiN coating exhibited higher hardness than TiN and nanolaminated AlCrN coatings. The nanolaminated AlCrN coating represented the highest adhesion ability in terms of critical load and the lowest coefficient of friction in comparison with the TiAlSiN and TiN coatings, respectively. The cutting performance, represented in terms of maximum flank wear as a function of cutting length, was found to be highest in the AlCrN coating. Oxides of these coatings, i.e., TiO2 for TiN, TiO2 for TiAlSiN and Cr2O3 for AlCrN, generated at different temperatures of 700°, 800° and 900°C, respectively. From all of results, it is obvious that the AlCrN coating exhibited more excellent wear resistance and oxidation resistance than the uncoated end mill, TiN coating and TiAlSiN coating.

Magnesium substituted hydroxyapatite formation on (Ti,Mg)N coatings produced by cathodic arc PVD technique

In this study, formation of magnesium substituted hydroxyapatite (Ca10−xMgx(PO4)6(OH)2) on (Ti,Mg)N and TiN coating surfaces were investigated. The (Ti1−x,Mgx)N (x=0.064) coatings were deposited on titanium substrates by using cathodic arc physical vapor deposition technique. TiN coated grade 2 titanium substrates were used as reference to understand the role of magnesium on hydroxyapatite (HA) formation. The HA formation experiments was carried out in simulated body fluids (SBF) with three different concentrations (1X SBF, 5X SBF and 5X SBF without magnesium ions) at 37°C. The coatings and hydroxyapatite films formed were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and FTIR Spectroscopy techniques. The energy dispersive X-ray spectroscopy (EDS) analyses and XRD investigations of the coatings indicated that magnesium was incorporated in the TiN structure rather than forming a separate phase. The comparison between the TiN and (Ti, Mg)N coatings showed that the presence of magnesium in TiN structure facilitated magnesium substituted HA formation on the surface. The (Ti,Mg)N coatings can potentially be used to accelerate the HA formation in vivo conditions without any prior hydroxyapatite coating procedure.

Tribological Properties of PVD CrAlN Coating Tools

The paper reports the tribological properties of the CrAlN coating tools at different speeds and loads. The coating was deposited on cemented carbide by cathodic arc physical vapour deposition technique. Ball-on-disc wear tests were performed on the CETR UMT-2 test system against SiC balls. The coating character and test results were obtained through SEM, XRD and Wyko surface profilometer. The results are as follows: The value of friction of coefficients decreased and depth of wear tracks became sallower as speeds increased and the coating presented adhesion phenomenon under low load. CrAlN coating showed excellent anti-wear properties at high speed and low load, and was more suitable for these similar working conditions.

Optimized coating procedure for the protection of TiAl intermetallic alloy against high temperature oxidation

The interest for TiAl intermetallic alloys is growing in the last years because of their excellent ratio between mechanical properties and density. However, the application is restricted at temperatures up to 873–973 K by the resistance to oxidation. For this reason it is of great importance to study protective coatings able to raise its temperature of performance above 1073 K.A TiAl3 layer was obtained on the surface of Ti–Al intermetallic samples, depositing an Al coating by arc Physical Vapour Deposition, followed by a thermal treatment. The microstructure and the composition of the coating were characterised before and after the thermal treatment by Scanning Electron Microscopy, X-Ray Diffraction, Focused Ion Beam and Glow Discharge Optical Emission Spectroscopy. The mechanical behaviour of the thermal treated layer was investigated by means of scratch tests and nano-indentation.Oxidations at 1123 K were carried out on coated and uncoated samples, in order to study the effect of the coating on the oxidation resistance of the samples. The aluminide coating provides a protection against oxidation in air at the considered temperatures due to its ability to form a continuous Al2O3 scale on the surface. The TiAl3 layer phase transformations occurring during high temperature exposition were also investigated.

Friction and Wear Behaviors of CAPVD TiAlN Coating

The paper reports friction and wear study of TiAlN coating at different speeds and loads. The coating was deposited on YG6 (WC+6 wt.% Co) cemented carbide by cathodic arc physical vapour deposition technique. Ball-on-disc wear tests were performed on the CETR UMT-2 test system against SiC balls. The coating character and test results were obtained through SEM, XRD and Wyko surface profilometer. The results are as follows: The value of friction of coefficients decreased and depth of wear tracks became smaller as speeds and loads increased. TiAlN coating showed excellent anti-wear properties at high speed and high load, and was more suitable for these similar working conditions.

Factors influencing properties of CrN thin films grown by cylindrical cathodic arc physical vapor deposition on HSS substrates

► Process parameter impact on properties of CrN films by cathodic arc PVD studied. ► High hardness and low surface roughness substrates conducive for adherent films. ► Optimized Cr ion etching yields superior film properties than Ti ion etching. ► Nitrogen partial pressure influences phase constitution and stress in CrN x films. ► Alternating high/low toughness CrN x multi-layers yield best film properties. The present study deals with growth of well-adherent and tough CrN thin films by cylindrical cathodic arc physical vapor deposition. The influence of substrate preparation parameters and deposition variables on film properties has been systematically investigated. The adhesion strength, hardness and crack propagation resistance (CPR) of the films were evaluated for different processing conditions. High substrate hardness and low substrate surface roughness were found to be conducive for obtaining well-adherent films. Cr ion etching was found to yield superior film properties, with the duration of etching also being a key determining factor. The nitrogen partial pressure employed during film deposition was noted to significantly influence the phase combination of the CrN x films as well as the stress levels in the deposited films. In case of multilayer CrN x films, alternating high toughness–low toughness layers were found to yield encouraging properties, with CPR values markedly higher than those obtained in mono-layer CrN x films, with no compromise in either hardness or adhesion strength.

Effect of cathodic arc plasma treatment on the properties of WC–Co based hard metals

In this study, ion bombardment in a cathodic arc physical vapor deposition system was applied on WC–Co hard metal surfaces aiming to benefit from the diffusion acceleration effect, and to investigate the role of this effect on the surface composition, morphology and corrosion resistance of the materials. Chromium ions obtained via cathodic arc evaporation were accelerated under low (−150V) and high (−1000V) bias voltages in order to apply coating–bombardment cycles to sample surfaces. Substrate temperatures were measured by an optical pyrometer during the processes. The treated samples were characterized by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). Temperature measurements showed that the sample temperature could be controlled precisely by adjusting the bias voltage. Temperatures in the range of 750–1200°C were measured during the treatment depending on the duration of the high bias voltage cycles. XRD analysis showed η phase formation in the near surface regions of all treated samples. The amount of the formed η phase was shown to be dependent on the heating–cooling regime that varied with the applied mode of bias. The corrosion behavior of the samples was investigated by immersing treated and untreated samples in a solution of 5% H3PO4 containing 1g/l Zn+2 for 24h at 50°C. The samples were investigated via SEM observations after immersion. Cathodic arc plasma treated samples showed a better resistance to corrosion in this environment.

Response to thermal cycling of duplex-coated hot work tool steels at elevated temperatures

Hot work tool steel samples were plasma nitrided and coated with a thin hard AlTiN film using the Cathodic Arc Physical Vapour Deposition process in the present work. The duplex-coated samples thus obtained were submitted to thermal cycling under conditions that mimic the steel thixoforming process. Compressive stresses generated at the surface due to a thermal expansion mismatch with the substrate lead to blistering of the AlTiN coating. These blisters produce wrinkles and develop into surface cracks with increasing number of cycles. AlTiN coating starts to spall off at those locations encircled by these cracks, leaving the substrate exposed to very hostile conditions. The nitrided substrate is very prone to oxidation and scaling is inevitable. Likewise, the nitrided surface fails to provide the required substrate support for the AlTiN coating as the hardening introduced at the surface by plasma nitriding is almost completely erased after only 350 thermal cycles. Having lasted for a maximum of 750 thermal cycles, the duplex-coated hot work tool steel fails to offer any improvement in the thermal fatigue performance of hot work tool steels at elevated temperatures.