WC-Co Substrates Research Articles

Arc-enhanced glow discharge ion etching of WC-Co cemented carbide for improved PVD thin film adhesion and asymmetric cutting edge preparation of micro milling tools

Wear-resistant thin films on cutting tools require effective ion etching to enhance adhesion and thus extended tool service life. Arc enhanced glow discharge (AEGD) ion etching, characterized by high ionization degrees and high etch rates, was applied to ultrafine-grained WC-Co cemented carbide, commonly used for micromilling cutters. The effect of AEGD ion etching on the surface integrity of WC-Co and the resulting adhesion behavior of a TiAlSiN thin film was investigated by varying the etching time in comparison with conventional glow discharge (GD) ion etching. In addition, the impact of intensive etching on the cutting edge geometry of micro end cutters and, in turn, on the cutting performance in micromilling of hardened and annealed high-speed steel was evaluated.AEGD achieves remarkable etch rates of 12 nm/min at extended etching times, which are 100 times greater than conventional glow discharge (GD) ion etching. Prolonged AEGD ion etching for ≥30 min removes entire near-surface WC grains and exposes carbides beneath, resulting in increased surface roughness. After the etching process, polished WC-Co substrates exhibit a slight reduction in residual compressive stresses, which steadily decrease with increasing AEGD ion etching time. Furthermore, a TiAlSiN thin film demonstrates high adhesion on AEGD-etched surfaces compared to GD ion etching. Even a brief 5 min AEGD ion etching ensures the highest adhesion class according to the Rockwell C indentation test. Moreover, the intensive material removal results in significant changes in cutting edge geometry of micro end cutters, yielding substantial cutting edge rounding and an asymmetrical shape with form-factors Κ ≥ 2. In cutting tests, the resulting cutting edge geometries effectively reduce the wear formation and the associated wear-related increase in process forces during micromilling hardened and tempered powder metallurgical high-speed steel. In summary, AEGD ion etching emerges as a highly effective method for both enhancing thin film adhesion and preparing adapted asymmetrical cutting edge geometries for micromilling tools.

Contrast Role of Third Body Layer and Hard Abrasives in the Wear Process of a TiAlSiN Hardness-Modulated Multilayer Coating: A Case Study on the Effect of Normal Load and Velocity

Working conditions exert an important influence on the tribological properties of protective coatings, thus affecting the wear resistance of workpieces. In this work, a TiAlSiN hardness-modulated multilayer coating with a good match of strength and toughness was deposited on WC-Co substrates. The adhesive wear played a predominant role under the condition of a larger normal load and lower velocity, leading to the formation of a third body layer composed of compressed and lubricating oxides. As a result, the wear rate of the coating tested at 20 N reduced by 23% of that tested at 5 N. Instead, abrasive wear was more manifest, leading to the formation of big-size abrasives, and thus the wear rate increased by 2.8 times while the velocity elevated from 4 mm/s to 16 mm/s. A full factorial analysis of the wear behaviors, including the nanohardness and roughness of the wear track, and the friction coefficient and wear rate of the coating, offered good guidance for the comprehension of the wear form of the TiAlSiN multilayer coating. The results demonstrated the optimization of multilayer structures for TiAlSiN coatings to attain better wear resistance under coupling conditions of normal load and velocity: harder or more lubricated sublayers.

Nozzle fouling in cold spray: Material transfer between Ni particles and WC-Co substrates at shallow impact angles and elevated surface temperatures

Experimental and theoretical investigations of nozzle clogging in WC-Co cold spray nozzles using nickel powder were conducted. Computational fluid dynamics (CFD) was used to show that the highest particle impact kinetic energy density occurs just downstream of the nozzle throat, where clogging is common. CFD also showed particles impact the nozzle wall at angles between 0.3°–5°, with smaller particles having higher velocities and temperatures. An experimental setup was used to investigate the effects of substrate temperature, surface roughness, and incidence angles on material deposition. Scanning electron microscopy revealed nickel particles smeared on the substrate surface, with more deposition on smoother surfaces. Energy dispersive X-ray spectroscopy (EDS) showed more nickel deposited at higher substrate temperatures and lower impact angles. Finite element simulations indicated nickel powder reaches temperatures above its melting point while sliding along the WC-Co substrate and predicted localized melting. Particle smearing is identified as the cause of nozzle clogging based on experimental and simulation results.

Stripping process of TiAlN/TiSiN coating on WC-Co cemented carbide substrate by using the dry-electropolishing technique

Physical Vapor Deposition hard protective coatings are frequently applied to hardmetal cutting tools to extend their lifespan under service-like working conditions. However, these coatings may experience damage during their performance, such as wear. In addition, defective coatings during the production process can occur, requiring reconditioning. In this sense, provided that the coating has not chipped off, removing and recoating the tools is a crucial process for their reuse, ultimately reducing costs. This study investigates the stripping process of an industrial ternary system (TiAlN/TiSiN) coating deposited on WC-Co cemented carbide using the dry-electropolishing technique. X-ray photoelectron spectroscopy was used to analyze the electrochemical surface changes. Chemical analysis reveals that a layer of oxide is created during the stripping process, mainly composed of SiO2, TiO2, and Al2O3, as well as organic compounds (e.g.: pyrrodic group in aromatics C-(NH)-C) and nitrogen oxides (e.g.: pyrinidic O=N-C). The stripping process successfully removed the coating without damaging the WC-Co substrate or leaching metallic Co binder. Additionally, the process follows a linear trend, establishing a correlation between the time of dry-electropolishing applied and the remaining coating thickness.

Interface characteristics of CVD diamond coating on WC-Co cemented carbide substrate

Chemical vapor deposition (CVD) diamond coatings on WC-Co substrates have gained significant attention due to their exceptional mechanical properties and wide-ranging applications in cutting tools, wear-resistant parts, and other advanced technologies. The interface bonding between CVD diamond coatings and WC-Co substrates plays a crucial role in determining the performance and durability of the coated tools. In this paper, the characteristics of the interface microstructures between the CVD diamond coating and WC-Co substrate was investigated by high resolution transmission electron microscopy (HRTEM) and EDS. The structures were observed in the system where the diamond coating (film) was deposited on the WC-Co cemented carbide substrate using HF-CVD technology. The results indicate three types of structures at the diamond coating-substrate interface: WC/diamond, WC/graphite/diamond, and Co/graphite/amorphous carbon/diamond. The bonding mechanisms at the CVD diamond coating/WC-Co substrate interface are discussed.

On wear of TiAlN coated tools with and without NbN overlayer in machining titanium alloys

Finding a wear resistant coating for cemented carbide cutting tools in the machining of difficult to cut Ti alloys is a challenge due to their high strength and chemical reactivity. Tool manufacturers recommend physical vapor deposited (PVD) TixAl1-xN (x = 0.4–0.7), and an extra NbN overlayer has shown promising potential. This study explores wear mechanisms of PVD Ti0.45Al0.55N with and without NbN overlayer and its WC-Co substrate in machining Ti alloys. To achieve an accurate understanding of tool-chip-workpiece interaction and related wear mechanisms, several approaches were employed. Tests with controlled variation of cutting speeds were complemented by process freezing experiments using the quick stop method and imitational experiments of diffusion couples. Advanced microscopy techniques were employed for accurate detection of wear products and phenomena across length scale. Findings reveal that any new design of coatings for Ti machining must combine both high mechanical integrity and resistance to diffusional dissolution and oxidation. Observed diffusional loss of Al and N from the coating results in a TiN layer which is mechanically weaker than the original coating, while the NbN overlayer reduces the Al diffusion rate, but NbN is subjected to diffusional dissolution itself. On dissolution, Nb stabilizes β-Ti and thus facilitating loss of Al, but the observed formation of intermetallic Nb3Al at the NbN–Ti interface works as a diffusion barrier. However, brittle Nb3Al can be more easily removed during machining. It was found that the coating retains longest on the edge line and protects the tool edge from failure because substrate cemented carbide wears at a faster rate than the coating with outward diffusion of C from WC grains and Co binder.

Multi-material laser powder bed fusion of embedded thermocouples in WC-Co cutting tools

During machining processes, due to deformation of the material and friction of the chip along the tool surface, a significant amount of heat is generated, particularly in the cutting zone, thus leading to a wear increase and consequent tool life reduction. Therefore, the ability to assess the cutting temperature in real time is extremely important to better understand heat generation, thus contributing to the development of more effective strategies for reducing machining costs and increasing tool life and productivity.This work proposes the fabrication of embedded additively manufactured K-type and N-type thermocouples in sintered WC-Co substrates by multi-material laser powder bed fusion for cutting temperature measurement in real time. Results showed that this approach is able to produce dense and continuous K-type and N-type embedded thermocouples with no evidence of severe defects, being found in the calibration tests a linear relationship with temperature, with a Seebeck coefficient at 20 °C of 40.8 μV/°C for K-type thermocouples and 16.5 μV/°C for N-type thermocouples. Turning tests revealed that the developed multi-material laser powder bed fusion approach is effective for manufacturing WC-Co cutting tools with 3D printed embedded thermocouples with the ability to measure precisely and accurately cutting temperature in real time during machining processes.

High-temperature tribological behavior of nanolayered TiAlN/TiSiN coating deposited on WC-Co cemented carbide

In this study, high-temperature tribological behavior of nanolayered TiAlN/TiSiN coating was evaluated against the Al2O3 counter-body using a pin-on-disk tribometer. The coating was deposited on the WC-Co substrate, in an industrial unbalanced magnetron sputtering system. Tribological tests were conducted at room temperature, 500, 600, 700, and 760 °C, in air and nitrogen atmospheres. After the tests, the coating was examined using confocal microscopy, tactile profilometry, scanning electron microscopy, focused ion beam, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and secondary ion mass spectrometry. The coating retained its microstructure and mechanical properties after exposure to high temperatures. At lower temperatures coating exhibited abrasive and adhesive wear mechanisms, while at higher temperatures abrasive and oxidative wear mechanisms were observed. In high-temperature tests, AlO, TiO and SiO were detected inside of wear tracks, in both atmospheres. However, the oxide thickness was significantly lower in tests with nitrogen atmosphere. Additionally, the top of the oxide layer was enriched in AlO with respect to TiO and SiO. The enrichment of AlO was more pronounced in nitrogen atmosphere. The coating tested in air exhibited slightly higher and more unstable coefficient of friction (COF) values, than in nitrogen atmosphere. This is attributed to the increased oxidation in air atmosphere. At room temperature tests in nitrogen, the wear rate was approximately 3 times lower than in air. At higher temperatures the wear rate was lower than at room temperature, in both atmospheres, due to formation of protective oxides. However, with the increase in testing temperature the wear rate increased. The reason for such behavior is the loss of substrate's and coating's hardness at high temperatures, and thickening of the oxide layer which accelerated its removal. The latter effect is not so pronounced in nitrogen atmosphere due to thinner oxide layer, which agrees with the lower wear rate in nitrogen atmosphere at high temperatures than in air.

Influence of Si Addition on the Chemical and Tribological Performance of TiAlCrN Coating Deposited by Co-Sputtering

In this work, nanostructured TiAlCrN coatings were deposited on a WC-Co substrate using a co-sputtering process varying the silicon composition on the coatings. The influence of silicon content on the mechanical, chemical, and tribological performance of the coatings was studied. The hardness increases from 11 to 16 GPa with the Si content; also, Young’s modulus increases from 260 to 295 GPa. The H/E ratio, which is a measure of materials’ ability to take the strain before deformation, is also increased with the increase in Si content, suggesting increased toughness. XPS analysis reveals that the coatings present titanium, aluminum, chromium, and silicon nitrides. The tribological behavior of the coatings was conducted through ball-on-disc tests, in which the results show that the coefficients of friction range from 0.15 to 0.55, with the lowest for the samples with the highest Si content. This behavior is benefited by the formation of oxynitride species, identified by XPS, which acts as lubricating layers and diffusion barriers. TiAlCrSixN coating presents a potential application for severe wear owing to its tribological performance.

In situ self-adaptive growth of graphene coatings on hard substrates via competitive NiCo catalysis reaction

Graphene coatings have sprung up as promising solid lubrication materials due to their intriguing mechanical properties. Achieving in situ deposition of a conformally encapsulated, high-quality graphene coating on hard substrates holds immense potential for industrial antifriction applications. However, the challenge persists in ensuring robust adhesion between graphene coatings and hard substrates (WC-Co), while minimizing excessive interfacial bonding to reduce growth energy consumption and friction. To tackle this problem, NiCo solid solution and competitive reaction strategies have been employed to achieve the in situ self-adaptive growth of graphene coating on WC-Co substrates with intimate interfaces. The high-temperature solid solution breaks through the physical diffusion barriers of the Co binding phase within the substrate to the Ni layer, facilitating the strong coupling effect at the NiCo-WC substrates. Experiments and density functional theory demonstrated that the accumulated Co atoms induce competitive reactions to inhibit the overlap of the electron cloud in Ni-C bonds, providing C atoms with sufficient energy to in situ segregate and diffuse laterally. Benefiting from the weakened interfacial covalent interaction and lower sliding energy barrier, graphene coating in situ deposited on substrates with deeper NiCo solid solution demonstrates superior macroscale low-friction and durability. Drawing on this design strategy, it is highly expected that hard substrate can be extended to diverse industrial surfaces composed of competitive metals for engineered graphene anti-friction applications.

Effects of Target-Substrate Distance on Growth and Mechanical Characteristics of Nanodiamond Composite Coatings Fabricated by Coaxial Arc Plasma Deposition on WC-Co Substrate

Effects of Target-Substrate Distance on Growth and Mechanical Characteristics of Nanodiamond Composite Coatings Fabricated by Coaxial Arc Plasma Deposition on WC-Co Substrate

The effect of current-carrying friction on the internal crystal phase of diamond coatings on WC-Co substrate

A great deal of attention has been paid to friction and wear caused by current-carrying friction. In this study, diamond coatings were deposited on the cemented carbides (WC-Co) substrate by hot filament chemical vapor deposition method. Although the diamond coating possessed a higher roughness than the WC-Co substrate, it was effective at reducing the friction coefficient and improving the effectiveness of WC-Co in the current-carrying friction process. In the presence of 1 A, the diamond coating exhibited a lower friction coefficient than the WC-Co matrix, and the diamond transformed into graphite as a result. The results show that diamond-coated surfaces have a better wear condition than WC-Co.

Designing selective stripping processes for Al-Cr-N hard coatings on WC-Co cemented carbides

Hard coatings like (Al,Cr)N are commonly used to protect cemented carbide cuttings tools from wear and corrosion. While such coatings increase the tool-lifetime, they also hinder the recycling effort of damaged tools. We report a new recycling strategy for coated cemented carbide tools by applying an interlayer between an arc evaporated Al0.7Cr0.3N coating and the WC-Co substrate. By selectively dissolving this interlayer in a concentrated basic solution, the coating spalls off the substrate, which is left intact. Four bases have been tested as saturated solutions: LiOH, NaOH, KOH, and CsOH, of which NaOH showed the highest reactivity. It was therefore used for subsequent investigations. Three different methods have been tested: (1) a metallic Al-doped interlayer region between substrate and coating can be removed in ▪ at ▪. Depositing an (2) Al0.7Cr0.3 or (3) Al0.9Cr0.1N interlayer leads to a significantly faster removal compared to the first method. Hereby a substrate could be fully de-coated in ▪ at only ▪. The reaction time was also decreased by pre-treating the samples in concentrated HCl, HNO3, or H2SO4 solutions at ▪ for ▪ before subjecting the samples to the NaOH bath. Such treated substrates were fully de-coated in ▪ at only ▪. While HNO3 oxidized the substrates significantly, HCl and H2SO4 caused only negligible substrate damage.

TiMoTa multi-component transition layer: Plasma in-situ diagnosis, mechanical properties and effect on diamond adhesion

The transition layer prepared on the cemented carbide surface through double glow plasma surface alloying (DGPSA) is believed to be an effective strategy to improve the adhesion between the diamond and cemented carbide. In this work, to fully reveal and understand the behavior of double glow discharge plasma, DGPSA processes were studied using optical emission spectroscopy (OES), and the effect of the as-prepared TiMoTa transition layer on the diamond growth mechanism and adhesion property was analyzed. The microstructure, composition, and adhesion properties of TiMoTa transition layers and diamond coating were analyzed using SEM, TEM, XPS, XRD, and Rockwell C indentation. The results indicated that the intensity of the plasmas (Ti, Mo, and Ta) remained stable with the deposition time with the increase of deposition temperature, the electron temperature remained in the range of 1 × 104–1.4 × 104 K during the deposition process. OES results showed that the TiMoTa transition layer with a high deposition rate and high performance can be prepared by selecting the appropriate deposition temperature and time through DGPSA technique. The TiMoTa transition interlayers with nanocrystalline structure can effectively restrain the out-diffusion of Co and the in-diffusion of C, thereby effectively improving the adhesion between diamond and cemented carbide. Hence, the TiMoTa transition layer prepared through DGPSA technique offers an effective way to develop a good adhesion diamond coating on WC-Co substrate.

Comparative Study of Mechanical Performance of AlCrSiN Coating Deposited on WC-Co and cBN Hard Substrates

The objective of this study is to explore and compare the mechanical response of AlCrSiN coatings deposited on two different substrates, namely, WC-Co and cBN. Nano-indentation was used to measure the hardness and elastic modulus of the coatings, and micro-indentation was used for observing the contact damage under Hertzian contact with monotonic and cyclic (fatigue) loads. Microscratch and contact damage tests were also used to evaluate the strength of adhesion between the AlCrSiN coatings and the two substrates under progressive and constant loads, respectively. The surface damages induced via different mechanical tests were observed using scanning electron microscopy (SEM). A focused ion beam (FIB) was used to produce a cross-section of the coating–substrate system in order to further detect the mode and extent of failure that was induced. The results show that the AlCrSiN coating deposited on the WC-Co substrate performed better in regard to adhesion strength and contact damage response than the same coating deposited on the cBN substrate; this is attributed to the lower plasticity of the cBN substrate as well as its less powerful adhesion to the coating.

The effect of WC-Co substrates on TiN/TiCN/Al2O3/TiCNO multilayer coatings

ABSTRACT In order to determine optimum substrate, TiN/TiCN/Al2O3/TiCNO coatings were deposited on WC-7Co substrate and WC-6Co substrate (named as Coating-7Co and Coating-6Co, respectively), and then the effect of WC-Co substrates on TiN/TiCN/Al2O3/TiCNO multilayer coatings was investigated by comparing the microstructure, hardness, adhesion strength, oxidation resistance and wear resistance of Coating-7Co and Coating-6Co. Results show that WC grain size of WC-6Co substrate is smaller, correspondingly the grain size of each layer in Coating-6Co is smaller, and the surface roughness is lower. Compared with Coating-7Co, Coating-6Co exhibits higher hardness, better plastic deformation capability, better oxidation resistance, lower friction coefficient and better short-period wear resistance. However, because of higher residual tensile stress and lower adhesion strength, the long-period wear resistance of Coating-6Co is worse than Coating-7Co conversely. To make good use of Coating-6Co, some post-deposition treatment techniques that can reduce residual tensile stress and improve adhesion strength should be considered.

A competitive-adsorption chemical vapor deposition method: Diamond coated on WC-Co substrate without acid-alkali pretreatment by adding graphene oxide particles

Detrimental components existed in substrate surface are regarded as a severe barrier of growing the chemical vapor deposition (CVD) coating. In this work, a novel competitive-adsorption CVD method was proposed to deposit the diamond coating on Co-cemented tungsten carbide (WC–Co) substrate without traditional acid-alkali pretreatment. Graphene oxide (GO) particles were adopted as the adsorbent to introduce the competitive adsorption with Co element during deposition. Four different GO concentrations were conducted to evaluate the effect of GO particles on the coating. The results shown that the WC-Co substrate with GO particles and without pretreatment can be covered by the integrated microcrystalline diamond (MCD) coating (GO-MCD) that presented the similar surface morphology to the MCD coated on WC-Co substrate with acid-alkali pretreatment (P-MCD). Furthermore, Raman spectra, AFM, XPS and XRD patterns only presented a slight difference between the GO-MCD coating and the P-MCD coating. Indentation test suggested that GO particles can enhance the adhesion strength and crack resistance of diamond coating. Meanwhile, GO particles did not deteriorate the tribological property of diamond coating. Hence, our proposed method might provide a promising approach to deposit the desired coating on the given substrate even with some detrimental components.

Structure and Frictional Properties of Ultrahard AlMgB14 Thin Coatings.

This paper presents the results of studies on AlMgB14-based ceramic coatings deposited on WC-Co hard alloy substrates using RF plasma sputtering. The aim of this work is to study the structure, phase composition, and mechanical properties of AlMgB14-based coatings depending on the sputtering mode. According to the results of the microstructural study, the bias voltage applied to the substrate during the sputtering process significantly contributed to the formation of the coating morphology. Based on the results of compositional and structural studies by energy dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy, it was found that the coatings are composed of nanocrystalline B12 icosahedrons distributed in an amorphous matrix consisting of Al, Mg, B, and O elements. The nanohardness of the coatings varied from 24 GPa to 37 GPa. The maximum value of the hardness together with the lowest coefficient of friction (COF) equal to 0.12 and wear resistance of 7.5 × 10-5 mm3/N·m were obtained for the coating sputtered at a bias voltage of 100 V. Compared with the COF of the original hard alloy substrate, which is equal to 0.31, it can be concluded that the AlMgB14-based coatings could reduce the COF of WC-based hard alloys by more than two times. The hardness and tribological properties of the coatings obtained in this study are in good agreement with the properties of AlMgB14-based materials obtained by other methods reported in the literature.

Surface Roughness Influence on Tribological Behavior of HiPIMS DLC Coatings

The application of diamond-like carbon (DLC) coatings in dry machining of difficult-to-machine materials has been gaining popularity due to high inertness, low coefficient of friction (COF), and high hardness of these coatings. Although the effect of surface roughness on the tribological properties of DLC coatings is of paramount importance, usually it is overlooked and coatings performance analysis was accomplished generally on highly polished substrates. The generation of polished surfaces is a time-consuming, labor-intensive process and, in most cases, not feasible for the industry due to its high cost. This article focuses on determining the effect of substrate (cemented carbide, WC-Co) surface roughness on the load-bearing capacity and tribological properties of DLC coatings deposited by High Power Impulse Magnetron Sputtering (HiPIMS) in Ne–Ar gas plasma. The DLC films were deposited onto WC-Co substrates with three different surface roughness profiles and their tribological performance were evaluated using a reciprocating tribotest. The high surface roughness resulted in increased wear rate due to high levels of asperities and increased potential for premature delamination of the coatings, while also causing severe damage to the counterbody due to inhibition of transfer film formation.

Effect of diamond seeds size on the adhesion of CVD diamond coatings on WC-Co instrument

In this study, we investigated the effect of the size of diamond seeds on the adhesion of multilayered polycrystalline diamond (PCD) films, grown by microwave plasma-assisted chemical vapor deposition (MPCVD). For that, identical WC-Co substrates were separately seeded by a set of diamond powders with various average particle sizes from water-based suspensions using similar seeding procedures. This investigation included powders with a difference in particle sizes of nearly 3 orders of magnitude: from 5 nm up to 2-4 μm. Seeded substrates were used to grow 8-10 μm thick multilayered PCD films using MPCVD with time-limited cycling injections of N2 gas. The Raman spectra and scanning electron microscopy (SEM) studies showed the similarity of microstructure and phase composition of all grown films, which confirmed that all films were grown in similar conditions. The performed scratch tests revealed sufficient differences in the adhesion of the films seeded with different diamond particles. The PCD film grown on 250-500 nm particles delaminated even before any mechanical investigations. The substrates seeded with 50 nm particles allowed the formation of the stable PCD film, but it started flaking under a load as small as 15 N. The 2-4 μm powder allowed the formation of PCD film with decent adhesion, which had local flaking under scratch test, which can be explained by the inhomogeneity of seeds distribution. Detonation nanodiamond (DND) powders allowed the formation of continuous diamond films with decent adhesion, however, powders with positive zeta potential were superior due to a much lower agglomeration of separate particles.