Structural and mechanical properties of AlTiN/CrN coatings synthesized by a cathodic-arc deposition process

Monolayered AlTiN and Multilayered AlTiN/CrN coatings were synthesized by a cathodic-arc deposition process, using TiAl (with 50/50 and 33/67 at.%) and Cr elemental cathodes. The atomic ratio of Al/(Ti + Al) in the AlTiN coatings was reduced to 0.44 and 0.61, respectively, compared with the corresponding Ti₅₀Al₅₀ and Ti₃₃Al₆₇ cathode materials. The multilayered AlTiN/CrN films showed smaller crystallite size, larger lattice strain, higher hardness, higher residual stress, and better adhesion strength as well than the monolayered AlTi films. The multilayered Al_0.35Ti_0.22N_0.43/CrN coating exhibited the highest hardness of about 38 GPa and the highest H³/E*² ratio value of 0.188 GPa, indicating the best resistance to plastic deformation, among all the coatings studied.     

Mechanical and tribological properties of multilayered TiSiN/CrN coatings synthesized by a cathodic arc deposition process

The monolayered TiSiN and multilayered TiSiN/CrN were synthesized by cathodic arc evaporation. The Ti/Si (80/20 at.%) and chromium targets were used as the cathodic materials. With the different I_[TiSi]/I_[Cr] cathode current ratios of 1.8, 1.0, and 0.55, the multilayered TiSiN/CrN coatings possessed different multilayer periods (Λ) of 8.3 nm, 6.2 nm, and 4.2 nm. From XRD and TEM analyses, both the monolayered TiSiN and multilayered TiSiN/CrN revealed a typical columnar structure and B1-NaCl crystalline, no peaks of crystalline Si₃N₄ were detected. Among the multilayered TiSiN/CrN coatings, the multilayered coating with Λ = 8.3 nm possessed higher hardness of 37 ± 2 GPa, higher elastic modulus of 396 ± 20 GPa and the lower residual stress of − 1.60 GPa than the monolayered (Ti_0.39Si_0.07)N_0.54 coating(− 7.25 GPa). Due to the higher Cr/(Ti +Cr + Si) atomic ratio, the multilayered TiSiN/CrN with Λ = 5.5 nm possessed the lowest friction coefficient. But the lowest of wear rate was obtained by the multilayered TiSiN/CrN with Λ = 8.3 nm, because of higher H³/E^?2 ratio of 0.323 GPa. The monolayered TiSiN possessed the highest wear rate of 2.87 μm²/min. Therefore, the mechanical and tribological property can be improved by the design of multilayered coating.     

Characterization of in situ synthesized TiC particle reinforced Fe-based composite coatings produced by multi-pass overlapping GTAW melting process

In this paper, in situ synthesized TiC particles reinforced Fe-based surface composite coatings by multi-pass overlapping gas tungsten arc welding (GTAW) melting process employing a proper amount of graphite and ferrotitanium (FeTi) on AISI 1020 steel substrate was produced. The microstructure and wear properties of the composite coatings were investigated by means of an electron microprobe microanalysis (EPMA), X-ray diffractometer and wear tester. The results showed that the multi-pass overlapping GTAW melting surface composite coatings can be obtained under suitable welding parameters, and no crack and porosity are found in the tracks. The X-ray and EPMA results confirm that TiC particles can be formed via reaction of FeTi and graphite during multi-pass overlapping GTAW melting process. TiC particles present cubic and dendrite shape in the non-overlapping zone. It is found that there occurred TiC particles coarsening at the overlap regions, which can lead to detrimental effects on the hardness and wear performance. Composite coatings give a high hardness and excellent wear resistance; and the wear friction coefficient of the coating is less than that of the 1020 steel. As a result, multi-pass overlapping GTAW melting process can be used effectively for producing surface composite coatings with a pre-placed powder to improve wear resistance of the AISI 1020 steel.     

High temperature tribological characterisation of TiAlSiN coatings produced by cathodic arc evaporation

This study reports on the wear properties at medium-high temperatures of TiAlSiN films deposited by cathodic arc evaporation on hot work steel substrates. The chemical composition and microstructure of the coatings were characterised by glow discharge optical emission spectroscopy, scanning electron microscopy and X-ray diffraction. The mechanical properties, i.e. hardness and elastic modulus were evaluated by nanoindentation, and the adhesion of the coatings was tested by scratch tests. Coatings with stoichiometries of Ti_0.31Al_0.1Si_0.06N_0.53 and Ti_0.23Al_0.12Si_0.09N_0.55 exhibit microstructures consisting of solid solutions of (Ti,Al,Si)N, where Al and Si replace Ti atoms. These films show high hardness and good adhesion strength to the hot work steels. Conversely, coatings with a stoichiometry of Ti_0.09Al_0.34Si_0.02N_0.55 show a wurtzite-like microstructure, low hardness and poor adhesion strength.The wear rates of the coatings were investigated by ball-on-disc experiments at room temperature, 200 °C, 400 °C and 600 °C, using alumina balls as counter surfaces. At room temperature, the films show wear rates of the same order of magnitude of TiN and TiAlN coatings. On the other hand, the wear rates of solid solution (Ti,Al,Si)N coatings measured at 200, and 400 °C are one order of magnitude smaller than those measured at room temperature due to the formation of oxide-containing tribofilms on the wear tracks. At 600 °C the wear rates increase but still keep smaller than those measured at room temperature, although this effect can be influenced by the softening of the steel substrates by over-tempering. EDS analyses revealed that, between 200 °C and 400 °C, the oxidation of the coating occurs only at the contact zone between the film and the counterpart body due to the sliding process.     

Microstructure and Corrosion Resistance of the AlTiN Coating Deposited by Arc Ion Plating

A new type of AlTiN coating containing about 29.13 at.% Al,16.02 at.% Ti and 54.85 at.% N was prepared by arc ion plating technology. The coating is composed of singular fcc-(Al, Ti)N phase and has no hcp-AlN phase to be formed. Due to the high content of beneficial element Al, the hardness and effective elastic modulus of the coating are up to 33.9 and 486.1 GPa, respectively. The adhesion strength between the coating and substrate is about 39.7 N. Electrochemical test shows that the corrosion current density of the AlTiN coating is nearly one-sixth of the substrate, and the charge transfer resistance R_(ct) of the AlTiN coating is much larger than that of the substrate, which means that the coating could act as a protective barrier between the substrate and corrosive electrolyte, enhancing the corrosion resistance.     

Characterization and sintering of nanocrystalline CeO2 powders synthesized by a mimic alkoxide method

Nanocrystalline CeO₂ powders of high sinterability have been successfully synthesized by a mimic alkoxide method, which employs alcohols as solvent, cerium nitrate hexahydrate as cerium source and diethylamine (DEA) as precipitant. Precipitation participating anions (OH⁻) are generated via the hydrolysis of DEA with the molecular water of the cerium salt. Irrespective of solvent type, the precursors produced by this method are CeO₂·2H₂O, which completely dehydrates to CeO₂ at temperatures >500°C. Calcining the precursors at 600°C for 2 h yields highly reactive CeO₂ powders with average crystallite sizes of ∼15 nm. These powders can be densified to >99% of the theoretical up to 1160°C in air at a constant heating rate of 10°C/min or to the same density by isothermal sintering at 1000°C for 2 h. The effects of calcination temperature and solvent type on powder characteristics and sinterability are also investigated.     

Friction and wear behavior of Cu-CeO2 nanocomposite coatings synthesized by pulsed electrodeposition

The friction and wear behavior of copper matrix nanocomposites reinforced with nanosized ceria particles, synthesized by pulse electrocodeposition technique, have been investigated. Tests have been carried out under dry sliding conditions by rubbing against a steel ball at varying loads ranging from 4 to 20 N and at constant speed of 11 rpm using a ball-on-disk wear tester. The experimental results indicate that the wear resistance of copper composite is superior to that of pure copper at all the loads and it improves with the increasing amount of ceria in the copper matrix. The friction coefficient and wear rates increase with the increase in applied load. When the load increases from 4 to 20 N, the transition of wear regime from local damage to delamination of a mechanically mixed layer (MML) occurs.     

可溶性阳极电刷镀纳米晶Ni-Fe合金镀层的退火再强化

采用可溶性Ni阳极电刷镀方法制备纳米晶Ni-Fe合金镀层,利用XRD、SEM、TEM、显微硬度计等测试方法分析低温退火对镀层结构和性能的影响.结果表明:纳米晶Ni-Fe合金镀层的硬度随退火温度的升高而提高,在200 ℃时达到最大值,存在明显的退火再强化;继续提高退火温度导致镀层硬度降低;400 ℃退火后的镀层硬度与镀态的接近;纳米晶Ni-Fe合金镀层退火过程没有出现晶粒异常长大,表现出比纯Ni镀层更高的热稳定性.     

Ti-Cr-B-N coatings prepared by pulsed cathodic-arc evaporation of ceramic TiCrB target produced by SHS

The method of pulsed cathodic-arc evaporation of composite targets based on self-propagating high-temperature synthesis has been applied for the first time to prepare nanocomposite coatings in the Ti-Cr-B-N system. The influence of the deposition-process parameters on the coating structure and properties has been studied. Structural investigations have been carried out using X-ray diffraction analysis, transmission and scanning electron microscopy, glow-discharge optical-emission spectroscopy, and optical profilometry. The coating properties have been determined by nanoindentation and tribological tests. The results of the study show that the coatings mainly consist of highly dispersed fcc phase based on Ti(Cr)N in the form of crystallites 1–2 nm in size; in addition, amorphous BNx phase has been found to exist in the coatings. The coatings obtained under optimal conditions have the following parameters: hardness 20–24 GPa, friction coefficient ～0.6, and reduced wear about 2 × 10^?6 mm³ N^?1 m^?1.     

电弧离子镀和高功率脉冲磁控溅射AlTiN涂层及其切削性能研究

目的 比较两种沉积方法制备的AlTiN涂层的切削性能.方法 利用高功率脉冲磁控溅射技术(HiPIMS)和电弧离子镀技术(AIP),在硬质合金车刀片上沉积AlTiN涂层,比较和研究两种AlTiN涂层的组织形貌特性及综合性能.利用扫描电子显微镜和X射线能量色散谱仪,观察和检测涂层的生长形貌和元素含量.采用激光共聚焦扫描显微...     

Tribological behavior of CrN/WN multilayer coatings grown by ion-beam assisted deposition

CrN monolayer coating and CrN/WN multilayer coatings were deposited on the silicon (100) substrate by ion-beam assisted deposition process. The bilayer period of these coatings was controlled at 8 nm and 30 nm. The cross-sectional morphology of nanoscaled multilayer coatings was characterized by scanning electron microscopy and transmission electron microscopy. The wear resistance of CrN/WN multilayer coatings and CrN monolayer coating was investigated using a pin-on-disc tribometer. The surface roughness (Ra) of the coatings was evaluated by atomic force microscopy, and that of CrN and WN monolayer coating was 6.7 and 5.9 nm, respectively. The employment of multilayer configuration in CrN/WN coating with bilayer period of 8 nm and 30 nm effectively reduced the surface roughness down to 1.9 and 2.2 nm, respectively. The friction coefficient of CrN monolayer coating and CrN/WN multilayer film with a bilayer period of 30 nm was 0.63 and 0.31, respectively. Owing to the high hardness/elastic modulus ratio, as well as the dense structure and the smooth surface roughness, the CrN/WN multilayer coatings exhibited better wear resistance in the consideration of friction coefficient and the worn surface morphology.     

Characterization of zinc oxide nanoparticles synthesized by polymer assisted deposition method

Zinc oxide nanoparticles (ZNPs) are synthesized onto glass substrates by employing simple and low cost solution based modified polymer assisted deposition (PAD) method. Trionx100 is used as a capping agent and zinc acetate as the zinc source. TritonX100 concentration is varied from 0.02 to 0.45 M for the synthesis of pure ZnO NPs. TG-DTA analysis was employed to determine the decomposition temperature of TritonX100 and zinc acetate, which lead to the formation of ZnO. The films were further characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HR-TEM), Fourier transforms infrared spectroscopy (FT-IR) and room temperature photoluminescence (PL). The results indicate that the synthesized nanoparticles (NPs) exhibits the room temperature PL with two emission peaks, one corresponding to ZnO band edge emission and the other one to point defect states created due to oxygen deficiency. The first peak undergoes blue-shift due to change in NPs size while there is no shift in the second peak. Nevertheless, with increase in TritonX100 concentration the peak intensity of defect peak decreases, indicating that the highly pure NPs have been successfully synthesized by PAD method.     

Wear-resistant Ti–B–N nanocomposite coatings synthesized by reactive cathodic arc evaporation

Wear-resistant Ti–B–N coatings have been synthesized by reactive arc evaporation of Ti–TiB₂ compound cathodes in a commercial Oerlikon Balzers Rapid Coating System. Owing to the strong non-equilibrium conditions of the deposition method, a TiN–TiB_x phase mixture is observed at low N₂ partial pressures, as determined by elastic recoil detection analysis, X-ray diffraction, X-ray spectroscopy, transmission electron microscopy and selected area electron diffraction. The indicated formation of a metastable solid solution of B in face-centered cubic TiN gives rise to a maximum in hardness (>40 GPa) and wear resistance on the expense of increased compressive stresses. A further saturation of the nitrogen content results in the formation of a TiN–BN nanocomposite, where the BN phase fraction was tailored by the target composition (Ti/B ratio of 5/3 and 5/1). However, the amorphous nature of the BN phase does not support self-lubricious properties, showing friction coefficients of 0.7 ± 0.1 against alumina. The effect of an increased bias voltage on structure and morphology was investigated from −20 to −140 V and the thermal stability assessed in Ar and air by simultaneous thermal analysis up to 1400 °C.     

Characterization and properties of quaternary Mo-Si-C-N coatings synthesized by magnetron sputtering technique

In this paper the direct current unbalanced reactive magnetron sputtering and composite target techniques were exploited to deposit quaternary Mo-Si-C-N coatings on Si wafer and stainless steel (1Cr18Ni9) in an Ar/N₂ gaseous mixture. The chemical composition, microstructure, morphology, hardness, and friction coefficient of these films were characterized by means of X-ray diffraction, XPS, field emission scanning electron microscopy, TEM and nanoindentation. With the increase of C content in the range of C/(C + Mo + Si + N) = 0-12 at.%, the crystallite size decreases from 32 nm to 5 nm and the average friction coefficient of Mo-Si-C-N coatings decreases from 0.24 to 0.17, while the hardness increases at first and then decreases after passing a maximum value of about 27 GPa at 9 at.% C. It was suggested that in the Mo-Si-C-N coatings C atoms substitute for the N atoms in the nano-sized crystalline Mo₂N to form Mo₂N(C) solid solution phase and the microstructure of the Mo-Si-C-N coatings may be nano-sized crystalline Mo₂N(C) embedded in the amorphous SiNx and CNx phases.     

Thermal plasma chemical vapor deposition of wear-resistant, hard Si-C-N coatings

Wear-resistant, hard Si-C-N coatings were synthesized in a triple torch plasma reactor using a thermal plasma chemical vapor deposition process. In this reactor, three dc plasma torches were angled so that their jets converge to form a highly chemically reactive region at the substrate. Vaporized hexamethyldisilazane (HMDSN) was injected through a central injection probe, while nitrogen or hydrogen gases were added through the torches to the argon plasma.Various dissociation, recombination and intermediate reactions were considered to determine what major species exist in the gas phase during the deposition of Si-C-N films. Reactant flow rates were varied to evaluate the thermodynamic equilibrium compositions across a linear temperature profile above the substrate and to identify the species that lead to the production of wear-resistant, hard Si-C-N films.A series of experiments were conducted at low HMDSN flows (∼ 1 sccm) and varying hydrogen and nitrogen flows. Films were characterized by micro X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Indentation tests were conducted on the polished film cross-sections, while wear tests were carried out on the film surfaces. At substrate temperatures below 1000 °C, amorphous Si-C-N films were deposited, while higher temperatures produced crystalline composite films of α- and β-Si₃N₄ and α- and β-SiC. Films produced with hydrogen at low HMDSN flows displayed non-columnar morphology and therefore had higher wear-resistance, indicating the benefit of low reactant-to-plasma gas flow concentrations on film growth. At low HMDSN flows, low nitrogen-to-hydrogen ratios had also shown an increase in film linear density. Small variations in mechanical properties and wear were observed between films grown under low N:H flow ratio conditions (smooth film surfaces). Wear-resistance of films with columnar structures from high N:H conditions was significantly lower, while the hardness was unobtainable. This result indicates the importance of film morphology on mechanical performance.     

Characterization of electrodeposited Ni-TiO2 nanocomposite coatings

Nanocomposites containing titania nanoparticles in a nickel matrix have been prepared by means of electrocodeposition from two different types of nickel plating baths, viz. an acidic sulfamate and an alkaline pyrophosphate bath. The surface charge and sedimentation behavior of the titania particles in these electrolytes were characterized by zeta potential and stability measurements. A maximum particle incorporation of 4.3 wt.% titania was found for the alkaline pyrophosphate bath. The structure and mechanical properties of the coatings have been investigated as a function of the particle content. The surface morphology and microstructure of the nickel matrix was significantly altered due to the presence of titania nanoparticles. In the case of both nickel baths, the Vickers microhardness showed a tendency to increase with the amount of particle incorporation. The wear resistance increased with decreasing current density and due to the particle incorporation.     

Zirconia coatings deposited by electrostatic spray deposition. Influence of the process parameters

The influence of electrostatic spray deposition (ESD) process parameters such as the substrate temperature, the precursor solution flow rate and the nozzle-to-substrate distance on the morphology of YSZ thin coatings was studied. Each parameter was studied separately and the correlation between them was found in order to optimise the experimental conditions where dense, continuous zirconia coatings can be successfully deposited.     

Influence of electrodeposition parameters on the deposition rate and microhardness of nanocrystalline Ni coatings

In this paper, nanocrystalline nickel (nc-Ni) coatings were prepared by a direct current electrodeposition technique. Their microstructure and microhardness were investigated by a high-resolution transmission electron microscopy and a microhardness tester. It is found that the electrodeposition parameters, including content of C₇H₄NO₃SNa?2H₂O, temperature and current density, have significant influences on the electrodeposition rate and microhardness of nc-Ni coatings. The electrodeposition rate increases with the current density stepwise. The largest electrodeposition rate is achieved at 60 °C. It decrease when the temperature is larger than 60 °C. The electrodeposition rate decreases with the increased content of C₇H₄NO₃SNa?2H₂O. The microhardnesses of the nc-Ni coatings are higher on the condition of the larger current density, lower temperature or higher content of C₇H₄NO₃SNa?2H₂O. But, it remains stable when the current density is in the range of 700-1000 A m^− 2. The relationship between the mean grain sizes and microhardness fits for the Hall-Petch function, approximately.     

Characterization of TiO2 coatings prepared by a modified electric arc-physical vapour deposition system

TiO₂ thin coatings were prepared, on various substrates, through evaporation of metallic titanium in an oxidizing atmosphere by modified electric arc-physical vapor deposition (EA-PVD). The coatings were characterized chemically (by means of XPS and SIMS) and from the structural point of view (by means of XRD and Raman spectroscopy), in order to understand the factors which lead to homogeneous coatings with high anatase content. The type of substrate is the main parameter that influences the crystal structure of the coatings: when stainless steel is used as substrate the coatings consist essentially of rutile, while on glass substrates coatings containing mainly anatase are obtained. The photocatalytic activity of the samples upon UVA irradiation was tested by using phenol as the target molecule. Phenol in the solution can be photocatalytically and rapidly degraded through the EA-PVD anatase TiO₂ coatings.