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Key engineering materials
Trans Tech Publications Ltd.
Key engineering materials

Trans Tech Publications Ltd.

半月刊

1013-9826

Key engineering materials/Journal Key engineering materials
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    Preparation and Characterization of Unique Foamy Zirconia Single Crystals via Sol-Gel-Hydrothermal Method

    Chang QibingZhou JianerWang YongqingMeng Guangyao...
    451-454页
    查看更多>>摘要：Porous ZrO_2 single crystals were prepared through a sol-gel-hydrothermal method and characterized by XRD, HR-TEM, SEM and FT-IR. The results show that the dried sol gel was converted into monoclinic zirconia crystals after calcined above 550℃. The zirconia single crystal has a porous structure with the crystal sizes of 20-70 nm. The origin of the pores was the gaseous hydrolysates of the superstoichiometric urotropine. The gel structure and the hydrothermal treatment are the required conditions resulting in the pores in crystals. After sintered at 1400℃, the disc of the obtained ZrO_2 crystals was dense. However, Y_2O_3 should be added to avoid fracture due to phase change if the disc was used as heat insulating layer.
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    • NETL
    • NSTL
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    Fabrication of Self-Healing Ceramic Coatings Against Oxidation for Carbon/Carbon Composites Using Polysilazane and B_4C Filler

    Chunying TianHongli Liu
    455-458页
    查看更多>>摘要：The self-healing ceramic coating against oxidation for carbon/carbon composites was fabricated via preceramic polymer pyrolysis process using polysilazane as preceramic and B_4C powder as filler. By means of SEM and XRD, the phase composition and the microstructure of coatings were characterized, and preliminarily study on its anti-oxidation ability and thermal shock resistance was conducted. The results showed that the parameters including content of B_4C, coating thickness, number of times of coating/pyrolysis play an important role on anti-oxidation ability of coatings. The optimal anti-oxidation ability was obtained when the content of B_4C reached 50wt%, the number of times of coating/pyrolysis reached three and 1200℃ was chosen as pyrolysis temperature. The thermal shock resistance test was conducted 50 times and the weight loss rate was 7.14% at 1000℃, which proved that the thermal shock resistance was excellent.
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    Preparation and Thermal Conductivity of Hf_6Ta_2O_(17) Ceramic

    M. LiQ. XuL. Wang
    459-461页
    查看更多>>摘要：Hf_6Ta_2O_(17) ceramic powder was prepared by solid state reaction at 1600℃ for 10 hours. The phase and microstructure of Hf_6Ta_2O_(17) ceramics were observed. The XRD results revealed that the sintered sample of the ceramic powder had single phase and the SEM results showed that the sintered sample was comparative dense. The thermal conductivity of the sintered sample was investigated and the value was comparative low.
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    Improving Ag-DLC Film Adherence on High-Speed Steel by Varying Ag Contents in A Mid-Frequency Dual-Magnetron Sputtering

    Yu XiangWang Cheng-biaoPeng Zhi-jian
    462-465页
    查看更多>>摘要：Aiming at improving their tribological behaviors, adhesion of diamond-like carbon (DLC) films on high-speed steel was investigated by varying doping silver (Ag) contents in a mid-frequency dual-magnetron sputtering system. Scratch testing was performed on the Ag-DLC films under a progressive normal load from 3 to 80 N, along with a Rockwell C indenter at a relative displacement speed for a Rockwell testing. A microscopic analysis of the scratch evolution under a progressive normal load permits identification of the various traces and the damage mechanisms of the films. A process of the film adhesion failure typically in turn appears like this, germination of the cracks along the longitudinal edges of the scratch traces; propagation in front of the indenter; and, detachment in the subsurface by shearing. An Ag-DLC film of 15.2 at% Ag exhibits a superior adherence on the steel substrate as compared with the three Ag DLC films of the other doping silver contents.
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    • NETL
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    Microstructure and Mechanical Properties of TiN/NbN Multilayered Coating

    Chien-Cheng LiuKuang-Yi LiuHuai-Wei YanChia-Li Ma...
    466-468页
    查看更多>>摘要：In this study, multilayers of TiN/NbN were deposited by d.c. magnetron sputtering on die steel substrates. The structure, morphology and nano-hardness were assessed using X-ray diffraction, atomic force microscopy (AFM), stylus profiler (XP-2 stylus profiler) and nanoindentation, respectively. Wear tests were performed on pin-on-disk configuration and dry sliding conditions, at 5N load by using hardened steel ball. The result shows TiN with highly (111) preferred orientation. On mechanical properties, Young's modulus and hardness values increase for layers number increase. At 64 layers films had the highest nano-hardness, Young's modulus values. The TiN/NbN multilayer films presented changes in its morphology becoming more granulated and density after heating up to 500℃ A significant decrease in friction coefficient has been achieved for TiN/NbN multilayers against steel ball.
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    Preparation and Oxidation Resistance of the Borate Glass Coating on Graphite Anode

    Yu XiaohuaZeng GuishengXie GangLi Rongxing...
    469-473页
    查看更多>>摘要：The protection coating, which was used on graphite anode, was developed. The materials were SiO_2, B_2O_3 and soluble glass as binder. The micrographic pattern, the phase composition and the components of borate glass coating were analyzed. The results indicated that the coating was morphology of borate glass at 700～850℃, the components were SiO_2, and B_2O_3 from XRD analysis, the coating could permeate into the pores of the graphite anode and seal the cracks developed by the coating, and it was adhesive strongly to the graphite anode from SEM analysis. The effects of the temperature and time on oxidation weight loss ratio and oxidation rate of graphite anode coating were observed and analyzed. The mechanism of oxidation resistance of the coating layer was explained. In addition, the thermal cycle experiments with the borate glass coating were done at 800℃ and 850℃, and the results demonstrated the sample had good ability of resistance to thermal shock.
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    • NETL
    • NSTL
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    Tribological behaviors of W-doped DLC films

    Fu Zhi-qiangWang Cheng-biaoDu Xiu-junPeng Zhi-jian...
    474-476页
    查看更多>>摘要：W-doped DLC films were synthesized from CH_4 and W by ion beam deposition and magnetron sputtering, and the influence of W target current on the surface morphology and the mechanical properties of W-doped DLC films deposited were studied. The W-doped DLC films in the study have a smooth dense surface with several particles of about 2micron. The hardness, the modulus, and the film-substrate adhesion of the films are increased with the rise of W target current and the critical load of the scratch test for all the W-doped DLC films is above 70N. The friction coefficient of W-doped DLC films is increased with the increase of W target current while the lowest wear rate is obtained when W target current is 1A.
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    W-doped DLC Films by IBD and MS

    Fu Zhi-qiangWang Cheng-biaoWang WeiPeng Zhi-jian...
    477-480页
    查看更多>>摘要：W-doped DLC films were synthesized from ethyne and tungsten by ion beam deposition and magnetron sputtering, and the influence of W target current on the structures and the properties of W-doped DLC films were studied. There exist some defects smaller than 3micron in W-doped DLC films and the influence of W target current on the defects is unobvious. The W content in the films is tardily increased with W target current below 3.5A, and then acutely rises with W target current. When target current is below 3.5A, the ratio of sp~3-C to sp~2-C is first decreased and then increased with the rise of target current, and the ratio of WC-C to sp~2-C is close to 0; but when the target is above 3.5A, the ratio of sp~3-C to sp~2-C is decreased and the ratio of WC-C to sp~2-C is augmented with further increasing target current. The hardness and the modulus is first decreased with target current and the minimum value is reached for the W-doped DLC films deposited with a target current of 2.6A. The W-doped DLC films deposited with a target current of 2.6A exhibit the best film-substrate adhesion. The W-doped DLC films deposited with a low target current exhibit a friction coefficient while the wear resistance of the W-doped DLC films deposited with a medium target current of 2.6A is best.
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    Titanium Nitride Coatings on Ti Alloys by PIRAC for Orthopedic Implants

    Shoujun WuE.Y. GutmanasI. Gotman
    481-484页
    查看更多>>摘要：In the present work, Ti and Ti-6A1-4V were PIRAC nitrided at the relatively low temperatures of 700-850℃. To obtain thicker TiN layers, 3 stage PIRAC based coating was applied: (1) PIRAC nitriding followed by (2) PIRAC titanizing followed by (3) additional PIRAC nitriding. The microstructure and phase composition of the obtained surface layers were characterized employing X-ray diffraction and scanning electron microscopy with chemical analysis (SEM/EDS). Bending test was employed to evaluate the coatings adhesion to the substrate. Lower PIRAC nitriding temperatures yielded smoother TiN coatings with a more gradual microhardness decrease from the surface to the bulk. All PIRAC TiN based coatings have excellent adhesion to substrate - no delamination of the coating in bending tests was observed. The best combination of microhardness and adhesion was obtained using 3 stage PIRAC process.
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    • NETL
    • NSTL
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    Insitu-fabrication of TiCN Ceramic Coating on Titanium Alloy by Laser Cladding Technology

    Yuling YangWei YanDuo ZhangGenzong Song...
    485-488页
    查看更多>>摘要：The insitu-fabrication of TiCN ceramic coating by laser cladding-laser nitriding technique (LC-LN) was investigated. Pulsed YAG laser with the power of 500W was used as radiation source. Highly pure N_2 was selected as the nitriding element; Titanium powder whose size is 20 μm and the pure carbon powder were utilized as the coating materials. The influence of technology parameters such as pulse width, pulse frequency and scanning speed etc. on the insitu-formation of TiCN ceramic coating was studied. XRD results show that the main phases of the coating are TiC_(0.3)N_(0.7) (or TiC_(0.2)N_(0.8)), TiN and TiN_(0.3). It was revealed that the appropriate process parameters for insitu-fabrication are the pulse frequency 15 Hz, pulse width 3.0ms, the scanning speed in the range of 9cm/min to 12cm/min, the pressure of N_2 0.4MPa. The result of OM showed a metallurgical bonding without crack and bubble between the coating and the substrate was obtained. The microstructure of cladded coating is characterized by fine dentrites. The average microhardness in the coating is more than 1300HV which is about 4 times of that in the substrate.
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