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Surface & Coatings Technology
Elsevier Sequoia
Surface & Coatings Technology

Elsevier Sequoia

0257-8972

Surface & Coatings Technology/Journal Surface & Coatings TechnologySCIISTP
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    Investigation of surface roughness post-processing of additively manufactured nickel-based superalloy Hastelloy X using electropolishing

    Jiang D.Tian Y.Zhu Y.Huang A....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.A major problem of additively manufactured parts using laser powder bed fusion (LPBF) is the as-built high surface roughness. The poor surface finishing is detrimental to the mechanical and electrochemical properties of the parts. In this work, we present systematic investigations on surface roughness reduction of LPBF produced nickel-based superalloy Hastelloy X (HX) using electropolishing. The electrolyte used in this study is an environmentally safe deep eutectic solvent (DES) comprising a eutectic mixture of choline chloride and ethylene glycol in a 1:2 M ratio, respectively. Two different groups of LPBF HX parts separated for the purpose of electropolishing the external and internal surface were prepared. The results show that both the external and internal surface roughness can be effectively reduced using electropolishing in DES. For the parts with the external surface electropolished for 5 min, a surface roughness reduction down to 1.2 μm (Ra) with a bright and reflective surface appearance was achieved. This is a significant improvement in comparison to the high as-built surface roughness of 10.3 μm (Ra) with a dull and non-reflective surface appearance. For the internal surface electropolishing, the surface quality of a 3 mm diameter internal channel in an angled LPBF HX cylindrical tube was successfully enhanced. The DES electropolishing efficiency on LPBF HX was investigated using weight reduction as a function of the electropolishing time, and the microstructure of the electropolished LPBF HX was studied. A further improvement of the electrochemical properties for the electropolished surface was revealed by anodic polarization tests and electrochemical impedance tests. The electropolished surface was also revealed to be more hydrophobic than the as-built surface by water contact angle tests, which is beneficial to the corrosion resistance. The findings herein demonstrate the surface quality of the LPBF produced HX can be effectively improved using electropolishing, and also showed the feasibility of using DES as a promising alternative electrolyte to the conventional hazardous acid mixtures.
      原文链接:
    • NSTL

    Effect of Ti/Si and Ti/TiN/Si interlayers on the structure, properties, and tribological behavior of an a-C film deposited onto a C17200 copper-beryllium alloy

    Santos M.D.Fukumasu N.K.Tschiptschin A.P.Souza R.M....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.Reduced hardness and wear resistance may limit SAE C17200 copper‐beryllium alloy use in manufacturing applications, such as plunger tips of die casting machines and as cores and inserts for steel dies in injection molding processes. In order to improve the surface properties of Cu—Be alloys, amorphous carbon (a-C) films have been selected since these coatings may show high hardness, low wear rate and low coefficient of friction. However, the adhesion of carbonaceous films on Cu—Be alloys remains a challenge. Two interlayer compositions (Ti/Si and Ti/TiN/Si) were deposited onto Cu—Be disks and silicon wafers to assess amorphous carbon adhesion on substrates made of Cu—Be alloy. The microstructure and topography of the coatings were examined by Field Emission Scanning Electron Microscopy (FESEM) coupled with X-ray dispersive energy spectroscopy (EDS). The chemical composition depth profile was measured by glow discharge optical emission spectroscopy (GDOES), which confirmed distinct coating layers of Ti, Si, a-C (C1 and C2 conditions-pDCMS). A TiN extra layer presence was obtained for the C3 and C4 conditions-pDCMS reactive, confirmed by small angle XRD analysis. Raman scattering spectroscopy showed a higher quantity of sp3 carbon bonds for C3 and C4 coating conditions compared to C1 and C2. Instrumented indentation tests indicated a higher hardness and reduced elastic modulus for C3 and C4 coating systems, corroborating Raman results, in terms of a higher concentration of sp3 bonds. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and coherence correlation interferometry (CCI) were used to characterize the coatings' surface features and scratch tracks after the tests. In addition, ramp load scratch tests were conducted to assess coating adhesion to the Cu—Be alloy substrate by measuring critical loads and the coefficient of friction. The highest critical loads to failure (Lc2) and (Lc3) were found for the Ti/TiN/Si interlayer sample (C4 condition), indicating that this interlayer improved the coating contribution to a gradual increase in the hardness and promotion of an enhanced adhesion strength of the a-C coating.
      原文链接:
    • NSTL

    Microstructure and electrochemical characteristics of CrMoN/Ag nanocomposite coatings in seawater

    Zhang M.Zhou F.Wu Y.Wang Q....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.CrMoN/Ag nanocomposite coatings with various Ag contents are deposited on Ti6Al4V alloys using closed-field magnetron sputtering, and their microstructures are detected by XRD, XPS and TEM. The electrochemical characteristics of CrMoN/Ag nanocomposite coatings are investigated using a three-electrode electrochemical workstation. The results show that the phase structure of coating contains (Cr, Mo)N solid solution and Ag crystallites. As the Ag content rises from 0.21 at.% to 4.86 at.%, the amount and size of Ag nanoparticle increase on the coating surface, and the cross-section feature of coating first becomes dense and then sparse. The corrosion resistance of coating in seawater is mainly dominated by its cross-section compactness and the amount of electrochemical active Ag. When the Ag content is 0.59 at.%, the dense cross-section and low surface roughness of coating contribute to its maximum open circuit potential of 0.173 V and charge transfer resistance Rct of 6.497 × 107 Ω∙cm2. But as the Ag content rises beyond 1.87 at.%, the potential drift range and power spectral density of coating gradually increase. Due to the occurrences of nanogalvanic corrosion and pitting corrosion, the corrosion resistance of coating is deteriorated, and then the corrosion current density icorr of coating continuously raises.
      原文链接:
    • NSTL

    Improved corrosion resistance of PEO-coated 7085Al alloy via a novel organic and inorganic sealing-treatment combination

    Huang J.Zhao D.Gong Y.Yang C....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.Combined the organic top-coats (Stearic acid (SA)) with inorganic salts (Cerium nitrate) sealing process, a novel sealing treatment was implemented on plasma electrolytic oxidation (PEO) coated 7085Al alloy to optimize the corrosion resistance in this work. The phase composition, surface morphology, wettability, roughness and electrochemical characterization results manifested that the sealing treatment was critical to the corrosion improvement. For the PEO-SA coating, the stearic acid should be chemically adsorbed on the PEO-SA coating after the sealing treatment. Herein, the stearic acid mainly reduced the surface energy of coating to achieve a hydrophobic structure, which was benefited to the corrosion resistance. Comparatively, the PEO-(SA + Ce) coating can further enhance anti-corrosion ability, which was attributed to the synergistic hydrophobic structure and sealing effects provided by Ce-based compounds. Finally, the underlying growth mechanisms of both coatings were proposed, and their corrosion behaviors were modelled and discussed analytically. Generally, this work has developed an efficient methodology to improve the corrosion resistance of protective coatings on Al alloys.
      原文链接:
    • NSTL

    Unraveling the formation mechanism of hybrid Zr conversion coating on advanced high strength stainless steels

    Nabizadeh M.Marcoen K.Terryn H.Hauffman T....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.This research unravels the formation mechanism of a hybrid conversion treatment including the well-established Zr conversion coating with a silane-based organic additive and Cu-based inorganic additive. The deposition mechanism of this coating was investigated on the thermal oxide film of Advanced High Strength Stainless Steels (AHSSS). This coating has been characterized using advanced surface analytical techniques such as XPS, FEG-AES, GDOES, and ToF-SIMS. The results showed that the simultaneous presence of these two additives results in the formation of a donor-acceptor complex between amine groups and Cu ions. The final coating contains Cu oxide together with a Cu-aminosilane complex, Zr oxide deposited mainly around Cu oxide and the aminosilane layer on the outer surface.
      原文链接:
    • NSTL

    Theoretical and experimental study of spontaneous adsorption-induced superhydrophobic Cu coating with hierarchical structures and its anti-scaling property

    Peng Y.Li P.Li H.Xin L....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.Some experimental studies have proven that micro/nano structured coatings achieve superhydrophobicity in air, without low-energy modification. However, it remains an issue how comprehensively explain the reason for changes in wettability. Herein, a hierarchically (nano-submicron-micro) structured Cu coating was fabricated on pipeline steel substrate by one-step electrodeposition. Notably, the superhydrophilic hierarchically structured Cu coating transforms to superhydrophobicity after stored in air for 15 days without chemical modification, with water contact angle of 151° and roll off angle of 3°. Both the microstructure and the chemical composition were characterized to understand the wettability transition mechanism. The fresh hierarchically structured Cu coating exists various defects, with high surface energy, which lead to superhydrophilicity. After the Cu coating stored in air, hydroxylation contributes to hydrocarbons adsorption, resulting in superhydrophobicity. The adsorption kinetic curve model shows that the hierarchical structure promotes hydrocarbon adsorption, which prominently reduces the transition time from superhydrophilicity to superhydrophobicity. The three-level wetting model is constructed to analyze the wetting state when water contacts the Cu coating, which verifies that it is the stable Wenzel-Cassie-Cassie wetting state. Moreover, the superhydrophobic Cu coating maintained anti-scaling property after immersing at 70 °C for 4 h. The anti-scaling behavior and mechanism of the superhydrophobic Cu coating were analyzed by both nucleation and wetting theories. The Cu coating also shows excellent self-cleaning property, water droplet impact resistance, and chemical stability. The superhydrophobicity of the Cu coating also maintained in weak acid and base solutions for 12 min. This study enriches and develops the theory and the technology in the field of wetting, and provides technical support and theoretical basis for the development of superhydrophobicity without low-energy modification.
      原文链接:
    • NSTL

    Improved bioceramic coatings reinforced by nanostructured talc

    Batista A.B.Stanley M.de Brito A.C.F.de Oliveira A.B....
    5页
    查看更多>>摘要：© 2022Nano-talc was successfully incorporated in the hydroxyapatite matrix via pulsed electrodeposition after being obtained using an eco-friendly liquid-phase exfoliation process. Scanning electron microscopy, atomic force microscopy, X-ray spectroscopy, Raman spectroscopy, corrosion and wear resistance, and cytocompatibility tests were used to characterize the biocomposite ceramics. Talc significantly improves the nanomechanical and wear properties of bioceramics (i.e., higher stiffness, reduced friction coefficient, and lower wear damage) as well as corrosion resistance. Talc does not induce cytotoxic activity in in vitro cells and may induce bone maturation as per biocompatibility tests.
      原文链接:
    • NSTL

    Chemical, physical, and mechanical characterization of chitosan coatings on a chemically pre-treated Ti6Al4V alloy

    Ferraris S.Riccucci G.Spriano S.Orlygsson G....
    5页
    查看更多>>摘要：© 2022 The AuthorsThe coating of titanium with chitosan is a promising way to reduce the infection risk and to modulate the inflammatory response of bone implants, but no effective coating procedure exists at the moment. Two titanium surfaces are tested in this research: a mechanically polished (as reference) and a chemically pre-treated one. Three coating strategies are followed: the direct linking at different pH (acidic and neutral), covalent bonding through a chemical activation of the titanium substrate (tresyl chloride) or through a linker molecule (polydopamine). The obtained coatings have been characterized by means of SEM, AFM, FT-IR spectroscopy, zeta potential titration curves, tape adhesion test, and soaking at physiological pH for 2 weeks. The best results, in terms of the degree of the surface coverage and stability of the interface, are obtained on the chemically pre-treated surface. Comparing the different coating procedures, in descending order of efficacy, we find the direct linking at acidic pH, covalent bonding through chemical surface activation, use of a linker molecule, and direct linking at neutral pH. The combination of a proper coating procedure and pre-treatment of the surface is effective in enhancing the electrostatic bonding of the coating to titanium.
      原文链接:
    • NSTL

    Tribological investigation of advanced coatings subjected to Venusian environment of 2.4 MPa CO2 pressure and 462 °C

    Tsigkis V.Bashandeh K.Polycarpou A.A.Lan P....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.Mechanical components in future missions to Venus will encounter high pressure (HP) and high temperature (HT) CO2 harsh conditions. Herein, the surface of Inconel 718 (INC 718), a HT nickel-based alloy was modified by applying advanced coatings by different deposition techniques. Three commercial coatings, namely Nedox PF-F™ (nickel-phosphorous alloy, referred as Nedox), Cera Tough™ (titanium-doped molybdenum disulfide alloy, referred as TiMoS2), and Balinit® DLC (amorphous hydrogenated diamond-like carbon, DLC) were coupled with PS400, a NASA-developed HT alloy, and slid against each other under HPHT Venusian-simulated environment. It was found that modifying one of the contacting surfaces (metal-on-coating) via PS400-deposition reduced the friction by 25%, whereas the wear increased significantly, compared to metal-on-metal contact. Sliding of the three coatings against PS400 coating (coating-on-coating) enhanced the frictional and wear performance significantly, in particular for PS400 vs. TiMoS2, attributed to the high wear resistance of the coating and the formation of beneficial oxide particles. The coefficient of friction (COF) was reduced by 38 and 43%, for PS400 vs. TiMoS2, and PS400 vs. DLC tribo-pairs, respectively compared to INC 718 vs. INC 718. In addition, the total wear rate decreased up to ten times, compared to metal-on-metal sliding.
      原文链接:
    • NSTL

    Tribological properties of flexible composite surfaces through direct ink writing for durable wearing devices

    Ma Z.Zhang X.Lu S.Yang H....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.Polydimethylsiloxane (PDMS), as a polymer material with excellent mechanical properties and flexibility, is widely used in flexible wearable devices, soft robots and other fields. Commonly, the Mold-flipping is used to produce PDMS based samples, while it is time-consuming and impractical for the large-scale fabrication. With the additive manufacturing, printing pastes can be freely configured thanks to direct ink writing (DIW) technology, enabling rapid and high precision manufacturing. Herein, we have improved the rheology of Sylgard-184 by adding crosslinkers and silica nanoparticles to make it printable. By adjusting the printing path, flexible surfaces with textures were created. Ball-on-disc dry friction experiments were carried out on the specimens. Results show that the texture produced by the print path can effectively reduce the coefficient of friction (COF) compared to samples produced by the conventional molding. When the print path is at 60° to the sliding direction, COFs for samples are reduced by 23.2% to 32.9%. Our findings provide a new strategy for preparing flexible and wearable devices through significantly enhancing the wear resistance of substantiable usage and prolonging the lifespan.
      原文链接:
    • NSTL