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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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    High velocity suspension flame spraying of AlN/Al2O3 composite coatings

    Blum M.Gyoktepeliler-Akin E.Killinger A.
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.In applications such as electronics and optoelectronics, where high heat exchange performance is required, the thermal conductivity of aluminium oxide is not always sufficient. To enhance the thermal conductivity, direct spraying of AlN using a supersonic suspension flame spray (HVSFS) process was investigated. Aqueous suspensions containing AlN powders, or mixtures of AlN and Al2O3 were used as a feedstock. Different combinations of axial and radial injections into the HVOF torch have been investigated and results are compared. The coating morphology and phase composition were analysed using optical microscope, SEM, WDS and X-Ray diffraction. Mechanical properties like microhardness and surface roughness have been measured. The aim is to create coatings with a high AlN content and thus higher thermal conductivity. Having these properties, this type of coating could be of excellent use in numerous electronic applications. The results show the highest AlN content in the coatings with axially injected pure AlN suspension. Moreover, the thermal conductivity values clearly correlate with the AlN content in the coating.
      原文链接:
    • NSTL

    Structure, mechanical and thermal properties of TiAlBN/TiAlN multilayers

    Sun X.Chen L.Zhou J.
    5页
    查看更多>>摘要：© 2022Building multilayer architecture is an effective path to improve comprehensive properties of Al-containing nitride coatings. Here, the cubic TiAlN insertion layers are introduced to stabilize their cubic growth of TiAlBN layers through a multilayer architecture of ML_1 (Ti0.42Al0.54B0.04N/Ti0.54Al0.46N) and ML_2 (Ti0.36Al0.55B0.09N/Ti0.54Al0.46N). Based on the template effect of cubic Ti0.54Al0.46N layer, ML_1 and ML_2 multilayers exhibit coherent interfaces between B-containing and Ti0.54Al0.46N sublayers, and thereby an overall single phase cubic structure. Meanwhile, compared to Ti0.36Al0.55B0.09N with hardness of 23.0 ± 0.6 GPa, our multilayers exhibit more exceptional hardness values of 32.4 ± 0.7 GPa for ML_1 and 36.2 ± 0.9 GPa for ML_2 due to the overall cubic growth and coherent interface strengthen effect. Besides, ML_1 and ML_2 reveal better age-hardening effect during annealing process whose hardness reach 34.7 ± 1.0 GPa for ML_1 at 900 °C, and 37.6 ± 0.6 GPa for ML_2 at 800 °C, respectively. The oxidation resistance of our B-containing coatings, which is significantly better than Ti0.54Al0.46N, depends largely on the average B content. After oxidation of 10 h at 850 °C, the oxide scales of B-containing coatings are ~1.12 μm for Ti0.42Al0.54B0.04N, ~0.56 μm for Ti0.36Al0.55B0.09N, ~3.27 μm for ML_1 and ~2.74 μm for ML_2, respectively, whereas the Ti0.54Al0.46N has been fully oxidized.
      原文链接:
    • NSTL

    Effect of energy distribution on the machining efficiency and surface morphology of Inconel 718 nickel-based superalloy using plasma electrolytic polishing

    Qian N.Su H.Zhang Z.Ding W....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.Inconel 718 nickel-based superalloys are important aerospace materials whose precision surfaces have important applications in key aerospace components. It is significant and challenging to obtain precise surfaces of Ni-based superalloys with high efficiency and quality. Plasma electrolytic polishing (PEP) is a rapidly developing high-efficiency and high-quality metal surface polishing process and is an application process for obtaining precise surfaces of superalloys. Research on the influence of vapor gaseous envelope (VGE) behaviors and the evolution process on the polishing effect remain insufficient, although the behavior of the VGE affects the machining efficiency and surface morphology of the superalloy. In this study, the evolution process of the VGE was analyzed and simulated using experimental and simulation methods. The effects of the VGE behavior characteristics on the surface morphology and polishing efficiency were explained from the perspective of energy distribution. The experimental results showed that a discontinuous and fluctuating VGE favored the removal of materials and finishing of the workpiece surface. When the voltage exceeded 400 V, the heat flux at the gas-liquid interface exceeded the critical heat flux, and the VGE evolved from bubbles to a vapor film which deteriorated the polishing effect. Finally, the voltage range for obtaining the precision surface of the superalloy was 250–350 V, while the temperature range of the electrolyte was 70–85 °C.
      原文链接:
    • NSTL

    Effect of gas nitriding on 316 L stainless steel lattice manufactured via selective laser melting

    Chen Y.Liu C.Wang J.Cui Y....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.Nitriding is well-known as a surface treatment method to improve the wear and fatigue properties. This work demonstrates the capability of nitriding in improving the overall mechanical performance of the open cellular structure, by taking the 316 L stainless steel lattice structure fabricated by additive manufacturing as an example. The microstructure, composition distribution, and compressive properties of the obtained structure were analyzed. It is found that the effective elastic modulus, compressive proof strength, and energy absorption capacity of the lattice were improved after conventional gas nitriding. A nitrided layer with a thickness of about 60 μm was formed on the surface of the nitrided parts, including an outer layer of chromium nitrides and an inner layer containing expanded austenite. The nitrided lattices with thinner struts were strengthened more due to the higher proportion of the nitrided layer. Meanwhile, the lattices were embrittled after nitriding. However, the toughness of the lattice can be compensated by adjusting the lattice structure, such as changing the angle between the strut and the compression direction so that a lattice with good strength and toughness can be obtained.
      原文链接:
    • NSTL

    Thermochemical post-processing of additively manufactured austenitic stainless steel

    Funch C.V.Somlo K.Christiansen T.L.Somers M.A.J....
    5页
    查看更多>>摘要：© 2022 The AuthorsThe effects of different thermochemical post-processing treatments on the microstructure and properties of additively manufactured austenitic stainless steel were investigated. If the nitrogen content in the as-built condition is high, austenitization in vacuum causes a reduction in nitrogen content near the surface. This can be remedied by applying a small amount of nitrogen in the gas during austenitization. Using high temperature solution nitriding, the surface hardness could be effectively raised by deliberate nitrogen ingress, while maintaining a very fine structure inside the primary austenite grains. The excellent combination of strength and ductility of the as-built condition is accompanied by a low degree of work-hardening. This condition showed elastic and plastic anisotropy. The vertically built condition exhibits a lower strength and an early initiation of yielding as compared to the horizontally built conditions. High temperature treatments were able to efficiently reduce the mechanical anisotropy exhibited in the as-built condition. A combination of high- and low temperature surface hardening was investigated using nitriding, carburizing and nitrocarburizing. In all cases expanded austenite developed on the surface, which created a strong hardness increase.
      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

    Structural evolution of amorphous and nanocrystalline TiAl films under helium implantation

    Liu P.Tian L.Li X.Xia J....
    5页
    查看更多>>摘要：© 2022The structure evolution and mechanism of the material during helium ion implantation are directly related to their performance and service life, towards the nuclear application. Despite the growing interest in amorphous and nanocrystalline films for a range of nuclear applications, many specifics about how their structure evolves during helium implantation are unclear. Here, the amorphous and nanocrystalline TiAl films produced by magnetron sputtering were in situ observed in a helium ion microscope to further understand the mechanism of microstructural evolution under severe ion implantation of two distinct structured nanomaterials. The result shows that a blister suddenly appeared on the surface of the nanocrystalline TiAl film, caused by a laterally ordered distribution of bubbles along the 〈111〉 crystal direction when the implantation dose reached 3.5 × 1017 ions cm−2. Instead, significant swelling of the whole implantation region of amorphous TiAl film was observed. At the final dose (9 × 1017 ions cm−2), the swelling thickness of the amorphous film was 200 nm and no exfoliation and cracking occurred. Due to long-range disorder, the degradation processes of amorphous TiAl film significantly differ from those of nanocrystalline TiAl film. This research has the potential to classify applications of materials in the nuclear field while providing a new viewpoint on the material structure design.
      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

    Revealing the deformation mechanisms of the heterogeneous structured CrMnFeCoNi high entropy alloy with ameliorated mechanical and corrosion resistance properties

    Li S.Li Y.Zou Y.
    5页
    查看更多>>摘要：© 2022Developing high entropy alloy (HEA) with both high strength and ductility is a longstanding challenge as potential structural materials. The strength and ductility trade-off can achieve via tailoring heterogeneous structures. Herein, a gradient structure with grain size variation from surface to center was successfully introduced into the CrMnFeCoNi HEA by ultrasonic nanocrystal surface modification (UNSM) process. More importantly, the deformation mechanisms and strengthening mechanisms of the heterogeneous structured CrMnFeCoNi HEA during tension were also investigated. Experimental results demonstrated that the heterogeneous structured CrMnFeCoNi HEA shows excellent strength and ductility combination properties ascribed to the grain refinement strengthening, dislocation density strengthening, and twinning strengthening. Besides, the corrosion resistance properties are also simultaneously improved, resulting from the low surface roughness, small grain size, and large compressive residual stress value. During tensile deformation process, the deformation mode is the dislocation slip at low strain and the slip system of the alloy is mainly {111}〈110〉. With the increase of deformation amount, twin crossing occurs, and grain size gradually decreases. The deformation mode changes from dislocation slip to twinning at high strain. In conclusion, the UNSM process ameliorates the comprehensive mechanical and corrosion resistance properties of CrMnFeCoNi HEA.
      原文链接:
    • NSTL

    Preparation of Ni-P-Ti3C2Tx-Ce composite coating with enhanced wear resistance and electrochemical corrosion behavior on the surface of low manganese steel

    Huang S.Li J.Zhang X.Han P....
    5页
    查看更多>>摘要：© 2022 Elsevier B.V.Ti3C2Tx, as a promising material, has attracted extensive attention due to its excellent properties. At the same time, Ce3+ is also a very effective corrosion inhibitor, which can play huge roles in anticorrosion. In this study, Ti3C2Tx-Ce powders were synthesized successfully by doping Ce3+ into Ti3C2Tx powders through a simple reaction. In addition, the Ni-P-Ti3C2Tx-Ce composite coating was synthesized by adding Ti3C2Tx-Ce particles into the Ni-P coating via an electrodeposition technique. Meanwhile, wear resistance performance studies have shown the coefficient of friction (COF) of the Ni-P-Ti3C2Tx-Ce composite coating is about 0.10, which is much lower than that of the Ni-P coating. The wear amount of Ni-P-Ti3C2Tx-Ce composite coating is only about 0.60 mg after 5 min of dry grinding under a load of 5 N and a radius of 5 mm. The microhardness of this composite coating has also been greatly improved, up to 3200 kg·mm−2. Furthermore, electrochemical corrosion behavior studies have shown the corrosion resistance (Rp) of the Ni-P-Ti3C2Tx-Ce composite coating is 120 times higher than that of the Ni-P coating, and 19 times higher than that of the Ni-P-Ti3C2Tx composite coating. The corrosion current of Ni-P-Ti3C2Tx-Ce composite coating is 3 orders of magnitude lower than that of Ni-P coating. Therefore, Ni-P-Ti3C2Tx-Ce coating is a promising material for device surface protection.
      原文链接:
    • NSTL