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Mao A.,Anhui University of Technology | Mao A.,Anhui Key Laboratory of Metal Materials and Processing
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2010

Electroless plating of Ni-P coating was carried out on sintered NdFeB magnets to improve their corrosion resistance. The best technological conditions such as metallic-ion ratio Ni2+ and H2PO2-, complexing agent concentration, stabilizing agent concentration, pH value, temperature and time were optimized by testing the rate of deposition and the number of pore per area. The number of pore per area of different type of Ni-P deposits and substrate were measured and the corrosion rate were also studied in the NaCl solutions of 3.5wt%, the HCl solutions of 10vol% and the NaOH solutions of 20wt%. The result shows that all the type of deposits enhance the corrosion resistance of substrate. Also the twice electroless plating Ni-P alloy provides the best protection, with bottom film alkaline Ni-P plated and top of film acid Ni-P plated. Source


Ran S.-L.,Anhui University of Technology | Ran S.-L.,Anhui Key Laboratory of Metal Materials and Processing | Wang D.-W.,Anhui University of Technology | Huang S.-G.,Catholic University of Leuven | And 2 more authors.
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2013

MB2-SiC (M=Ti, Zr) composites were prepared by reactive pulsed electric current sintering using MH2 as raw materials. The results indicated that the composites had a slightly textured structure with MB2 grains oriented with their (001) planes perpendicular to the direction of pressure and DC current. Fine MH2 powders improved densification and orientation of MB2 during reactive sintering process. Due to the orientation of MB2 grain, the MB2-SiC composites exhibited mechanical anisotropy. The TiB2-SiC composites showed high fracture toughness with the highest value of 7.3 MPa·m1/2 and the ZrB2-SiC composites had a high flexural strength with the value of 937 MPa, respectively. Source


Hou Q.Y.,Hefei University of Technology | Hou Q.Y.,Anhui Key Laboratory of Metal Materials and Processing | Luo L.M.,Hefei University of Technology | Huang Z.Y.,Anhui Key Laboratory of Metal Materials and Processing | And 3 more authors.
Fusion Engineering and Design | Year: 2016

Tungsten coatings with 1.5 wt.% TiC (W/TiC) were fabricated by atmospheric plasma spraying (APS) and supersonic atmospheric plasma spraying (SAPS) techniques, respectively. The results showed that the typical lamellar structure of plasma spraying and columnar crystalline grains formed in the coatings. Pores located mainly at lamellar gaps in association with oxidation were also observed. TiC phase, distributed at lamellar gaps filled the gaps; and that distributed around un-melted tungsten particles and splashed debris coated the particles or debris that were linked with the TiC at lamellar gaps. The coating and linking of the retained TiC phase prevented the tungsten particles to come off from the coatings. The porosity and the oxygen content of the SAPS-W/TiC were lower than those of the APS-W/TiC coating. The mechanical response of the coatings was strongly dependent on the H/E∗ratio (H and E∗are the hardness and effective Young's modulus, respectively). The SAPS-W/TiC coating with a higher H/E∗ratio had a better ability to resist to elastic fracture and better fracture toughness as compared with the APS-W/TiC coating with a smaller H/E∗ratio. The thermal conductivity of the SAPS-W/TiC coating was greater than that of the APS-W/TiC coating. © 2016 Elsevier B.V. All rights reserved. Source


Hou Q.Y.,Hefei University of Technology | Hou Q.Y.,Anhui Key Laboratory of Metal Materials and Processing | Luo L.M.,Hefei University of Technology | Huang Z.Y.,Anhui Key Laboratory of Metal Materials and Processing | And 3 more authors.
Surface and Coatings Technology | Year: 2016

In this work, as a kind of rare earth hydrides, 1.5 wt.% LaH2 powder was introduced into a tungsten powder and then deposited by a supersonic atmospheric plasma spraying (SAPS) machine. The purpose was to form La2O3 in the LaH2-doped tungsten-based coating. The microstructure and properties of the undoped and LaH2-doped tungsten-based coatings were characterized using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), nano-indentation tester and Vickers hardness tester. The results showed that SAPS coatings exhibited typical lamellar microstructure. Pores located mainly at lamellar gaps in association with oxidation were also observed. The type of tungsten oxide was mainly WO3. During SAPS process, La2O3 was formed in the LaH2-doped tungsten-based coating by the transformation of LaH2. The formed La2O3 was distributed mainly at lamellar gaps, having a joining effect on the adjacent lamellae. The oxygen content, porosity and thermal conductivity of the LaH2-doped tungsten-based coating were lower than those of the undoped tungsten coating. The introduction of 1.5 wt.% LaH2 in the tungsten coating improved its ability to resist elastic fracture and improved its fracture toughness. © 2016 Elsevier B.V. Source


Hou Q.Y.,Hefei University of Technology | Hou Q.Y.,Anhui Key Laboratory of Metal Materials and Processing | Luo L.M.,Hefei University of Technology | Huang Z.Y.,Anhui Key Laboratory of Metal Materials and Processing | And 3 more authors.
Surface and Coatings Technology | Year: 2016

In this work, as a kind of rare earth hydrides, 1.5 wt.% LaH2 powder was introduced into a tungsten powder and then processed by atmospheric plasma spraying (APS) to form a coating. The oxidation characteristics and laser irradiation melting characteristics of the tungsten coatings with or without LaH2 addition were investigated and compared. The results showed that the coatings exhibited typical splat/lamellar microstructure. WO3, which was distributed between lamellar layers or in splats, formed in the APS-W coating by the oxidation reaction between W and O2. The introduction of LaH2 in the tungsten-based coating led to forming WO2 by a deoxidization of WO3. La2O3 with a morphology of long strip, which was distributed mainly between lamellar layers and had a filling effect on the pores, formed in the APS-W/LaH2 coating by the oxidation reaction between La/LaH2 and WO3/O2. The oxide/oxygen content and the porosity of the APS-W/LaH2 coating were apparently lower than those of the APS-W coating; and the relative density and thermal conductivity of the former were higher than those of the latter. The trends of the crack to form in the APS-W/LaH2 coating were lower than that in the APS-W coating when the two types of coatings were irradiated by a laser. The coarse elongated tungsten grains formed in laser irradiation melting sample for the APS-W coating. But the fine equiaxial tungsten grains formed in laser irradiation melting sample for the APS-W/LaH2 coating, which was mainly the result of the pinning effect of the re-precipitated spherical La2O3 particles on the re-crystalline tungsten grain boundaries. The ability of the APS-W/LaH2 coating to resist high heat loading was greater than that of the APS-W coating. © 2016 Elsevier B.V. Source

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