WC Substrate Research Articles

Laser stripping of TiAlN coating to facilitate reuse of cutting tools

The potential of using the laser ablation process to perform controlled stripping of titanium aluminium nitrite (TiAlN) coating from tungsten carbide (WC) substrate is explored in this paper. TiAlN coatings are extensively used in cutting tools to improve machining capability, and to extend the life of the tools. However, if any error is detected on the coated tools, or when the tooling needs to be reused, it is mandatory to remove the existing coating to facilitate reshaping/recoating. The existing coating removal process uses chemical stripping methods, which are not environmentally friendly and not suitable for selective coating removal. In the present work, excimer laser removal of TiAlN from coated WC flat plates has been studied and demonstrated as a viable alternative to existing chemical stripping methods. The ablation thresholds of the TiAlN coating and WC substrate were identified as 1.85 J/cm2 and 2.3 J/cm2 respectively. The paper also presents experimental and theoretical evidence of the process mechanism responsible for laser stripping of TiAlN coatings

Ammonia decomposition activity on monolayer Ni supported on Ru, Pt and WC substrates

Catalyst design for specific reactions currently involves using atomic or molecular descriptors to identify promising catalysts. In this paper, we explore three surfaces that have similar computed nitrogen binding energies, which is a descriptor for the ammonia decomposition reaction. The surfaces studied include a monolayer of Ni on Pt(111), Ru(0001) and tungsten monocarbide (WC). The activity of these surfaces toward the ammonia decomposition reaction was compared using density functional theory and temperature programmed desorption. It was found that while the NHx–H bond scission is similar on each of the surfaces, the temperature of nitrogen desorption is very different. The differences are explained and the implications for ammonia decomposition activity and catalyst design are discussed.

Effects of bias on properties of Ti–C:H films coated by filtered cathodic vacuum arc

A bias voltage apparatus is attached to the filtered cathode vacuum arc system for coating a diamond-like film containing Ti on WC substrate. Ti, which acts as the cathode target, is sputtered by plasma, and reacts with C2H2 gas, then deposits on the WC under working conditions of 60 A current and voltage between −50 and −275 V. Such processed diamond-like film containing Ti(Ti–C:H) is analysed by glow discharge spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and nanoindentation for determining Ti concentration, crystallographic structure, bonding mode and mechanical properties. Characteristic parameters are determined to obtain suitable properties, and the underlying reasons are also addressed.

Defect Structures in Diamond Composite Coated Cemented Tungsten CarbideSubstrates

Variability in the abrasive wear of PCD coatings on cemented WC substrates has been investigated. Six samples of PCD coated carbides were tested in a wear testing rig. The PCD coated element was used to turn an industry standard vitrified bonded corundum grinding wheel. The wear rate was measured as the weight loss of the cutting element per cubic metre of grinding wheel machined during the test. Two grades of cutting elements were observed. One grade had wear rates between 6 and 7.3 g/m³ but of the three poor quality samples, only one valid test was made realising wear rate of ~7,800 g/m³. The microstructures of the samples were studied using SEM, X-ray imaging, neutron diffraction and XRD. SEM images revealed differences in the volume percentage of diamonds in the two grades and the XRD scans highlighted the variable distribution of the diamond phase in the coating. Estimates of the residual stresses in a good and poor quality samples indicated significantly higher compressive stresses in the good quality versus poor quality coating. These results have revealed two extremes in the wear rates of these PCD coated carbides. It is suggested that the difference in diamond content between the two grades is not sufficient to account for the 3 orders-of-magnitude difference in the observed wear rates. However, the presence of intrusive veins of carbide material in the coatings, especially around the curved cutting tip, suggested that the macroscopic defects observed in the x-ray and SEM images were the major cause of the high wear rates in the poor quality sample.

Structure and tribological properties of AlCrTiN coatings at elevated temperature

In this study, we analyzed the high temperature tribological behavior of AlCrTiN coatings deposited on WC substrates by low cathodic arc technique. The coatings chemical composition, Al 31at.%, Cr 16at.%, Ti 7at.% and N 46at.%, and the bonding state were evaluated by X-ray photoelectron spectroscopy. The mechanical properties of the coatings were studied by scratch-test and nanohardness depth sensing indentation. The morphology of the coatings surface, ball scars, wear tracks and wear debris as well as the oxidized samples was examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The structure was analyzed using X-ray diffraction (XRD). Wear testing was carried out using a high temperature tribometer (pin-on-disc) with alumina balls as counterparts. The evaluation of the friction coefficient with the number of cycles (sliding distance) was assessed at different temperatures and the wear rates of the coatings and balls were determined; the maximum testing temperature was 800°C. The coating showed an excellent thermal stability and wear resistance. The friction reached a maximum at 500°C and then decreased, whereas the wear rate was negligible up to 600°C and increased significantly at higher temperatures.

Atomic Layer Deposition of Pt on Tungsten Monocarbide (WC) for the Oxygen Reduction Reaction

Atomic layer deposition (ALD) was utilized as a synthesis method to deposit monolayers of Pt onto WC substrates for applications as oxygen reduction reaction electrocatalysts. Samples utilizing various Pt ALD cycles were characterized using surface analytical methods and scanning electron microscopy, whereas cyclic voltammetry was used to determine whether the oxygen reduction reaction takes place on the catalyst surface. ALD Pt was found to deposit onto WC substrates following an island growth mechanism. When few Pt ALD cycles are used, discrete Pt particles first formed and dispersed over the WC substrate, but at least 100 ALD cycles is required for the WC substrate to be covered with Pt. Whereas Pt monolayers are not obtained, ALD Pt on WC still shows activity for the oxygen reduction reaction. Cyclic voltammetry conducted in an O2-saturated 0.5 M H2SO4 electrolyte indicate that as few as 20 Pt ALD cycles on WC is needed to produce oxygen reduction reaction activity that is comparable to Pt bulk. Effor...

The Influence of Interlayer for Frictional Property and Adhesion of IBAD CNx Coating

The carbonaceous hard coating such as Diamond-Like Carbon is one of the materials to prevent surface damage. It was reported that Carbon Nitride (CNx) coating showed superlow friction coefficient when it slid against a Si3N4 ball in N2 environment. In the case of applying CNx coating for industrial fields, it is necessary to improve adhesion between CNx coating and substrate. In this study, we clarify the effect of interlayer to improve adhesion of CNx coating to WC substrate. 4 different kinds of interlayer materials were prepared. From the scratching test results, adhesion of using CrN and no interlayer was smallest. On the other hand, SiN, CN and DLC interlayers showed high adhesion. From the finite element analysis, interlayer thickness and Young's modulus did not affect to improve adhesion between CNx coating and WC substrate.

Mechanical behavior of TiN/CrN nano-multilayer thin film deposited by unbalanced magnetron sputter process

TiN and CrN single layer thin films along with TiN/CrN multilayer thin film, which has an average layer thickness of 4 nm were deposited on WC substrates by a commercially used unbalanced DC magnetron sputtering. The microstructure and mechanical properties of the as-deposited films were investigated. The TiN/CrN multilayer thin film has a single phase structure with the preferential orientation of (2 0 0), a finer surface morphology and a finer columnar crystal structure. Additionally, the TiN/CrN multilayer thin film also shows better adhesion on substrate and hardness than the single layer thin films. The hardness of the annealed multilayer thin film is slightly increased after annealed at temperatures of 600–800 °C. This is attributed to the increased intensity of (1 1 1) reflection during annealing.

Structure and mechanical properties of Ti–Al–N coatings deposited by combined cathodic arc middle frequency magnetron sputtering

Ti–Al–N coatings were deposited on Si (1 1 1) and WC substrates by combined cathodic arc middle-frequency magnetron (MF) sputtering under a Ti arc power of 10 kW and with different Al MF targets currents. X-ray diffraction patterns (XRD) showed that the Ti–Al–N coatings were polycrystallize with a preferred (1 1 1) orientation at 2 θ = 43.7°. The (1 1 1) diffraction showed a decrease in peak intensity but a increase in FWHM values with the increasing of Al contents. Nano-meter sized TiN crystal grains distinguished by the lattice fringe contrast were verified by plan-view transmission electron (TEM) and selected area electron diffraction (SAED) images. With the increasing of MF sputter currents from 5 to 20 A, the Al contents in the Ti–Al–N coatings monotonically increased from 4.8 to 10.8 at.%, whereas the N and O contents were nearly constant. The hardness of the Ti–Al–N coatings was in the range of 23–32 GPa, and the Young modulus values were in the range of 420–540 GPa.

Improvement in the tribological performances of Si 3N 4, SiC and WC by graphite-like carbon films under dry and water-lubricated sliding conditions

Silicon nitride (Si 3N 4), silicon carbide (SiC) and cemented carbide (WC) are good material candidates in the applications of water hydraulic systems and related water-lubrication fields. But high friction and severe wear would arise from the unavoidable solid–solid contact during running-in period, frequent starting/stopping due to the absence of effective water lubrication. Graphite-like carbon (GLC) films with high hardness was successfully deposited on above different ceramics to improve their durability and stability under different working conditions. The microstructure, morphology and mechanical characteristics of the as-deposited GLC films were investigated by Raman spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and nano-indention tester. The tribological behaviors of GLC-coated Si 3N 4, SiC and WC were comparatively studied by a ball-on-disc tribo-meter when compared with un-coated ceramic substrates under both dry and water-lubricated sliding conditions. Results show that the friction coefficient of coated-GLC films kept a relatively lower value of 0.04–0.07 whereas the above three ceramic substrates demonstrated a much higher value in the range of 0.1–0.3 under both dry and water-lubricated conditions. In addition, the wear rate of Si 3N 4, SiC and WC substrates could be significantly reduced after the deposition of GLC films and interestingly the GLC-coated WC exhibited unique super-low wear rate (nearly non-wear properties). The tribological performance of coated-GLC films greatly depended on the ceramic substrates and the corresponding friction-reduction and anti-wear mechanisms related with different wear conditions and substrates were also revealed. Such GLC films are considered as potential protective and lubricating surfaces for water-lubricated parts such as water-lubricated bearing, mechanical seals and other moving parts used in water environment.

Reactive wetting and infiltration of polycrystalline WC by molten Zr 2Cu alloy

Good wettability with equilibrium contact angles of 41–28° was achieved for molten Zr2Cu alloy on dense polycrystalline WC substrates at 1050–1150 °C in an Ar atmosphere, favoring pressureless infiltration of the molten Zr2Cu alloy into a porous WC preform. Interfacial microstructure examination revealed that the Zr2Cu alloy reacted with WC, yielding W and ZrC at the interface through a solution–precipitation mechanism.

Tribological Performance of CrAlSiN Coatings at High Temperatures

AbstractChromium aluminum nitride (CrAlN) coatings produced by PVD are routinely deposited on tools and tested as components for machining and forming applications. However, the addition of a doping element, such as Si, can further improve the properties of such coatings. In this study, CrAlN and CrAlSiN coatings with different Cr/Al ratio were prepared on WC substrates by low cathodic arc deposition and their structure and tribological properties analyzed in situ at high temperatures. In spite of excellent thermal stability and oxidation resistance, the hot‐sliding tests showed unsatisfactory coating behavior.

Annealing Ni nanocrystalline on WC–Co

The effects of annealing temperature on nanocrystalline sputter-deposited Ni thin films (500 nm) deposited on WC–Co (4 wt.%) were investigated. Special attention was focused on quantitative evaluation of residual stress and Ni diffusion into the WC–Co, after heat treatment, from 873 to 1273 K. The estimated level of residual stress, as measured by X-ray diffraction, is around −1.3 ± 0.1 GPa for the as-deposited film, whereas after annealing at 1273 K it decreases significantly. Atomic force microscopy shows that high annealing temperature results into an exponential increase of the roughness. An intermixing between the nanocrystalline Ni and the Co from WC substrate occurs, as it is revealed by quantitative depth-resolved Rutherford backscattering spectrometry analysis and also supported by X-ray photoelectron spectroscopy. We ascribe a significant stress relief with the increasing annealing temperature to the diffusion process. The understanding of this process is particularly important in WC–Co parts with the surface treated with Ni in order to improve the maximum surface service temperature.

Laser removal of TiN from coated carbide substrate

Sustainable manufacturing requires the extended usage of materials and reuse of hard metal tooling. In general, titanium nitride (TiN) coating gives enhanced hardness and wear resistance to the surfaces of engineering tools. However, the high hardness makes it difficult to re-grind or refurbish TiN-coated materials, especially TiN-coated cutting tools. This paper presents the results of laser decoating of TiN from TiN-coated tungsten carbide (WC) substrates. Laser decoating was performed using a KrF excimer laser. The effect of laser fluence, number of pulses, frequency, scanning speed and beam overlap on the decoating performance was investigated in detail. A two-dimensional symmetric finite element model (FEM) was established to elucidate the temperature and stress fields created during the laser decoating process. Successful laser decoating of TiN coating from the WC substrate was demonstrated. It was found that decoating with a laser fluence of 4 J/cm2, scanning speed of 2 mm/s, frequency of 25 Hz and a beam overlap of 91% gives best results for removing an area of TiN coating to its 3 μm thickness. The surface roughness of the best samples was found to be in the order of 0.8–0.9 μm Ra. The experimental and FEM investigation suggested that the decoating of TiN follows combined explosion and evaporation mechanism.

Effects of ion implantation on structures of ion-plated carbon films

A Raman spectroscopic study has been carried out on the effects of ion implantation of argon or nitrogen on the structures of ion-plated (IP) carbon films. The carbon films were deposited on WC substrates at room temperature, 200, 250, 300 and 350 °C. Implantation of 150 keV Ar + or N ＋ into the films was carried out with a fluence of l × 10 16 ions/cm 2 at room temperature. The structure of the carbon films was estimated by laser Raman spectroscopy. It was found that the Raman spectra for non-implanted and implanted IP carbon films consisted of four main peaks: two wel1-known peaks belonging to graphite and long-ranged-disordered graphite structures, and two other new peaks which can be considered as follows. One peak corresponds to a polyacetylene-like carbon (PALC) structure with C C bonding, and the other peak corresponds to a part of PALC with chains of alternate C C and C–C bonds. The as-deposited IP carbon films had various structures depending on the ion plating conditions. Ion implantation in IP carbon specimens changed their structures making them all the same. It is expected that mutual transfer equilibrium (PALC ▪graphite) was achieved during ion implantation.

Characterization of ultra-fast deposited polycrystalline graphite by a CO 2 laser-assisted combustion-flame method

High deposition rate, 750 μm/min, crystalline graphite was deposited on WC substrates by a CO 2 laser-assisted combustion-flame method at laser powers between 300 and 800 W. The structures, which were identified as pillars, were characterized by various methods. The pillars were cylindrical in shape and grew to a size of approximately 3 mm in length and in a few minutes. The laser power did not affect the overall length of the pillar, but caused changes in the physical shape. X-ray and electron diffraction results revealed the pillars to be crystalline graphite regardless of the laser power. Investigation of the pillars by scanning electron microscopy showed two distinct microstructural areas: an inner core of dense material surrounded by an outer shell of lamellar-like material. The core/shell microstructure was unaffected by the level of CO 2 laser power.

Ion beam assisted DC magnetron sputtering에 대한 렌즈 유리 성형용 WC 합금의 Ir-Re 박막 특성

Ir-Re thin films with Ti interlayer were deposited onto the tungsten carbide substrate by ion beam assisted DC magnetron sputtering. The Ir-Re films were prepared with targets of having two atomic percent of 7:3 and 5:5. The microstructure and surface analysis of the specimen were conducted by using SEM, XRD and AFM. Mechanical properties such as hardness and adhesion strength of Ir-Re thin film also were examined. The interlayer of pure titanium was formed with 100 nm thickness. The film growth of Ir-30at.%Re was faster than that of Ir-50at.%Re in the same deposition conditions. Ir-Re thin films consisted of dense and columnar structure irrespective of the different target compositions. The values of hardness and adhesion strength of Ir-30at.%Re thin film coated on WC substrate were higher than those of Ir-50at.%Re thin film.

Investigation of the microstructure and characterizations of TiN/CrN nanomultilayer deposited by unbalanced magnetron sputter process

In this study, TiN, and CrN, monolayer thin films and a TiN/CrN multilayer thin film were deposited onto WC substrates by unbalance DC magnetron sputtering. Single-layer TiN and CrN thin films were prepared at various nitrogen flow rates (20–30 sccm). TiN/CrN multilayers with a monolayer thickness of 4 nm were also deposited on the WC substrates. The morphology, and crystalline structures of the as-prepared films were characterized by SEM and XRD, and their mechanical properties and thermal stabilities were also evaluated. The experimental results show that the grain size of the columnar structure increased with the nitrogen flow rate. The increase in the size of the grains in the columnar structure, however, can be minimized with an applied bias voltage of 100 V. When the nitrogen flow rate was increased from 20 to 30 sccm, β-Cr 2N transformation to CrN was observed, while the TiN structure remained unchanged. The hardnesses of the TiN and CrN thin films were ~ 23.9 and 21.4 GPa, respectively. A significant increase in the hardness of the TiN/CrN multilayer thin film to 34.9 GPa (4 nm interval) could be observed. Scratch test results also show that the multilayer has more desirable properties than the monolayers. The critical load for the TiN/CrN multilayer thin film (45.0 N) was higher than that for the TiN (~ 24.8 N) or CrN (~ 37.3 N) monolayer thin films. After annealing at 800 °C, no significant phase transformation and decrease in mechanical properties of the TiN/CrN multilayer thin film could be observed.

Tool life performance of multilayer hard coatings produced by HTCVD for machining of nodular cast iron

Abstract In this study, tool life performance of multilayer hard coatings was evaluated for machining of nodular cast iron. With this regard, TiCN+TiC+TiCN+Al 2 O 3 +TiN and TiCN+TiC+TiCN+Al 2 O 3 +TiN multilayered coatings with different thicknesses were fabricated on WC substrates using high temperature chemical vapor deposition (HTCVD). These cutting tools with hard multilayered coating systems were used in longitudinal turning of nodular cast iron under cutting condition encountered in the shop floor. To investigate the tool life performance in cutting tools coated by HTCVD method, cutting experiments were performed in CNC turning bench by using three distinct cutting tools having multilayered hard coatings and WC insert with square edges, and two types of nodular cast irons. Cutting speed, depth of cutting, and feed rate were kept as constant values. Tool life based on flank wear was the parameters considered to compare the three cutting tools. It was found that TiCN+TiC+TiCN+Al 2 O 3 +TiN (T3) multilayer coating with 10.5 μm thick exhibited better performance according to all parameters.

A Combined Surface Science and Electrochemical Study of Tungsten Carbides as Anode Electrocatalysts

An effective anode electrocatalyst in direct methanol fuel cell (DMFC) should have high activity for the oxidation of methanol and the decomposition of water, while remaining stable under the relatively harsh anode environment. Although the Pt/Ru bimetallic alloy is currently the most effective anode electrocatalyst, both Pt and Ru are expensive due to limited supplies and both are susceptible to CO poisoning. Consequently, the discovery of less expensive and more CO tolerant alternatives to the Pt/Ru catalysts would help facilitate the commercialization of DMFC. In this paper we will discuss the possibility of using tungsten carbides (WC) and Pt-modified WC as potential anode electrocatalysts in DMFC. We will provide an overview of our recent work, using a combined approach of fundamental surface science studies and in-situ electrochemical evaluation of the activity and stability of tungsten carbides. We will demonstrate the feasibility to bridge fundamental surface science studies on single crystals with the electrochemical evaluation on polycrystalline WC films. We will also discuss the synergistic effect by supporting low coverages of Pt on the WC substrate to further enhance the electrochemical performance of WC.