Table of Content

    25 June 2022, Volume 33 Issue 12
    Progresses of Surface Engineering in Extreme Environments and Its Common Scientific Problems
    CHANG Keke, CHEN Leilei, ZHOU Ruonan, XIAO Xuelian, WANG Fangming, WANG Liping
    2022, 33(12):  1388-1417.  DOI: 10.3969/j.issn.1004-132X.2022.12.001
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    The strong coupling effects from multi factors in the typical extreme environments of “three depths and one pole” (deep space, deep sea, deep earth and polar) led to the coexistence of multimode damages and failures, such as material corrosion, wear, fatigue, and fracture, which bringed severe challenges to the high precision, high reliability, and ultralong service life of mechanical systems. Surface engineering technology was one of the most effective ways of surface strengthening and life extension. The researches of relevant methods and basic scientific problems were important supports for structural optimization and material designs of highsafety and highreliability mechanical engineering equipment in extreme environments. The general methods of surface engineering technology and their applications in the fields related to extreme environments were introduced, the common basic scientific problems of surface engineering in extreme environments were analysed, focused on the implements of theoretical calculation methods in solving problems, and the development directions of surface engineering in extreme environments were commented.
    Effects of Laser Cladding Process Parameters on Microstructure and Residual Stresses of Fe-based Double Layer Coatings
    ZHOU Jiali, CHENG Yanhai, CHEN Yongxiong, LIANG Xiubing, BAI Chengjie, DU Wang
    2022, 33(12):  1418-1426,1434.  DOI: 10.3969/j.issn.1004-132X.2022.12.002
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     Aiming at the problems that the components had high crack sensitivity due to the intense temperature field changes accompanied by stress and strain evolution in laser cladding processes. The evolution of residual stresses under different laser scanning paths and processing parameters was studied. Fe-based multilayer coatings were prepared by laser cladding on Q345 steels. The residual stress distribution along the coating depth was measured by X-ray diffraction method combined with electrochemical corrosion stripping method. The effects of laser scanning path, power and scanning speed on the microstructure and stress distribution of the coatings were investigated. The results show that the residual compressive stress occurs on the surface and inside of the coatings, the residual stresses changes at the coating-substrate fusion line, and the heat-affected zones are of the residual tensile stress. Laser cladding processes have significant influences on the size and distribution of residual stresses for coatings. When laser scanning path is contour bias, power is as 1.8 kW and scanning speed is as 0.02 m/s, the coatings have the best residual stress distribution and forming quality. The residual stress is mainly related to the impacts of laser beams on the molten pool and the non-equilibrium solidification characteristics of the cladding layers.
    Influence Law and Mechanism of Texturized Controllable Interfaces on Leakage of Steam Turbine Regulating Valves
    LIAO Yihong, ZHANG Guiming, XU Jing
    2022, 33(12):  1427-1434.  DOI: 10.3969/j.issn.1004-132X.2022.12.003
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    Based on the theory of fluid lubrication, the pressure distribution and leakage of steam turbine control valves were calculated by finite element method, the influence law of textured controllable interface on the leakage of the control valves was analyzed, the action mechanism of textured control valves was clarified, and the interface regulation was realized. The results show that the designed hydrophilic and hydrophobic textures meet the expected wettability, the hydrodynamic lubrication of micro pits is poor. The dynamic pressure balance texture has dynamic pressure wedge effect and obvious eddy currents, which may effectively improve the hydrodynamic lubrication of clearances between valve stem and valve sleeve. However, the dynamic pressure balance texture increases the connecting area of upper and lower walls, which is not conducive to sealing. The influences of leakage reduction rates of texture from large to small is hydrophobic texture, combined texture, hydrophilic texture and dynamic pressure balance texture. When the pressures on the regulating valves exceed 3.5 MPa, the leakage reduction rate changes gently. Hydrodynamic lubrication, sealing dam effect and the synergy of eddy current energy exchange and energy dissipation in the grooves make the combined texture superior to other textures in improving the stability of valve stems and reducing leakages.
    Study on Tribocorrosion Behaviors of AlNiZr Amorphous and Nanocrystalline Composite Coatings
    ZHANG Zhibin, ZHANG Shuyan, LU Nan, CHEN Yongxiong, LIANG Xiubing
    2022, 33(12):  1435-1443.  DOI: 10.3969/j.issn.1004-132X.2022.12.004
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    In order to improve the corrosion and wear resistance of steel structure materials in marine extreme environments, a new kind of AlNiZr amorphous and nanocrystalline composite coating was prepared by high velocity arc spraying technology. The tribocorrosion behaviors of the AlNiZr coatings in 3.5 wt.% NaCl solution were studied. The results show that the arc-sprayed AlNiZr coatings have uniform microstructure and good density. The phase structure is composed of amorphous, nanocrystalline and crystalline phases. The volume fraction of amorphous phases in AlNiZr coatings is as about 64.93%, the average microhardness value is as 363 HV0.1, and the average bonding strength between the coatings and 45 steel is as about 30.8 MPa. Under the dry friction conditions, the arerage friction factor, wear volume and wear width of AlNiZr coatings are about 0.125, 0.134 mm3, and 882.4 μm, respectively. The wear failure mechanism of the coatings is mainly oxidative wear and brittle delamination wear, accompanied by slight abrasive wear. Under the corrosive conditions, the average friction factor, wear volume and wear width of the coatings decrease significantly due to the lubrication and antifriction of corrosive medium, which are about 0.058, 0.02216 mm3 and 314 μm, respectively. The corrosion wear failure mechanism of the coatings mainly exhibites in the form of delamination wear, and wear plays a leading role, followed by corrosion. Compared with the pure aluminum coatings, the AlNiZr coatings show excellent corrosion and wear resistance.
    Thin Shell Structure Enhanced Nanocomposite Coating for Deep-sea High Pressure Sound Absorption
    FU Yifeng , WANG Huming, CAO Pan
    2022, 33(12):  1444-1451.  DOI: 10.3969/j.issn.1004-132X.2022.12.005
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    The effects of high pressure on a nanocomposite coating named PSM with high acoustic absorption coefficient only under normal hydrostatic pressure were investigated. To improve the underwater sound absorption properties of PSM under high pressure, a shell structure was proposed to minimize the pressure effects on PSM by a hard shell combined with a soft layer whose superior sound absorption performance was maintained under high hydrostatic pressures. FEM simulation and compression experiments show that 2 mm thick epoxy as the hard shell enhances the compression strength of PSM, and 2 mm thick Ecoflex absorbs the residual deformations in the center. The underwater acoustic tests show that the underwater sound absorption coefficient of PSM with epoxy and Ecoflex as the protection is from 0.2 to 0.7 in a frequency range of 1500~7000 Hz under high pressure as 1.5 MPa.
    Experimental Study of Load Carrying Performance of Water Lubricated PCD Thrust Bearings for Rim Driven Thrusters
    LIANG Xingxin, ZHANG Sen, QI Shihuang, JIN Shuanbao
    2022, 33(12):  1452-1458,1467.  DOI: 10.3969/j.issn.1004-132X.2022.12.006
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    In order to solve the problems of weak load carrying capacity and short service life of water lubricated thrust bearings of ship rim driven thrusters(RDTs), a heavy load bearing scheme was proposed using superhard polycrystalline diamond(PCD) as friction pairs. Several sets of PCD thrust bearings with diamond grain sizes of 10 μm, 25 μm and 35 μm were manufactured respectively. These bearings were tested on a bearing test bench and further on a RDT prototype. The results of the bench test show that friction coefficient of PCD thrust bearings with grain size of 10 μm fluctuates violently under heavy load conditions, while the bearings with grain size of 25 μm and 35 μm may work stably under the specific pressure of 20 MPa. This specific pressure is 40 times higher than that of the water lubricated thrust bearings with conventional soft/hard materials matching pairs used in the existing RDTs. The stable friction coefficient is about 0.015 when the rotating speed is 400 r/min, and there is no sign of wear in tens of testing hours. The PCD bearings with grain size of 35 μm passed the test assessment under harsh working conditions such as start and stop, acceleration and deceleration, high-speed and heavy load on the RDT prototype for one month. It is proved that PCD thrust bearings are competent for RDTs under heavy load conditions and extremely harsh working environments.
    Research Progresses of Dense Environmental Barrier Coatings with High Water Vapor Corrosion Resistance
    DONG Lin, YANG Guanjun, ZHANG Xiaofeng, LIU Meijun, ZHOU Kesong, LI Pu, ZHU Changfa, XU Xiangyi, LIU Kun
    2022, 33(12):  1459-1467.  DOI: 10.3969/j.issn.1004-132X.2022.12.007
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    EBCs were coated on the surfaces of SiC-CMCs to effectively isolate the engine corrosive environment and avoid rapid corrosion failure of the components, which become the key for the applications of SiC-CMCs to hot section components of gas turbine engines. However, interconnected pores were formed in coatings, causing rapid degradation in a combustion environment containing high-temperature water vapor and oxygen. The research progresses of the effects of EBCs materials properties, preparation technologies, and processing parameters on the pore structure were summarized. The effects of pore structure on the water vapor corrosion resistance was analyzed, and the research progresses of EBCs densification were summarized. Finally, future research on the preparation of dense EBCs to improve their water vapor resistance was prospected.
    Environmental Adaptability and Tribological Properties of MoS2/WS2 Composite Films
    FAN Xin, REN Siming, WANG Haixin , PU Jibin
    2022, 33(12):  1468-1476.  DOI: 10.3969/j.issn.1004-132X.2022.12.008
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    The hot and humid atmosphere had a serious deteriorating effect on the tribological properties of the MoS2 lubricating films. Unbalanced magnetron sputtering technology was successfully used to prepare WS2 doped MoS2 composite films, and the addition of a small amount of WS2 in the MoS2 matrix might induce the preferential growth of MoS2 along the(002) crystal planes, the film structure became denser, the penetration and diffusion of corrosive media were significantly inhibited, and the MoS2/WS2 composite film exhibited high salt spray corrosion resistance, low friction coefficient and wear rate. The composition-optimized MoS2-1.6at.%WS2 composite film was only oxidized on the surface layers after 4 days of salt spray, and still maintained a low friction coefficient of 0.16 and a low wear rate of 3.80×10-6 mm3/(N·m). 
    Tribological Properties of Mo/MoS2-Pb-PbS Composite Films in Vacuum Environments
    HAN Cuihong, MA Guozheng, LI Guolu, SHI Jiadong, WANG Haidou,
    2022, 33(12):  1477-1483.  DOI: 10.3969/j.issn.1004-132X.2022.12.009
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    The performance of lubricating films under harsh working conditions might be improved by multicomponent compounding.Composite process of “radio frequency magnetron sputtering + low-temperature ion sulfide” was adopted to deposit Mo/MoS2-Pb-PbS composite films on 9Cr18 bearing steels. Tribological properties of Mo/MoS2-Pb-PbS composite films were evaluated by MSTS-1 vacuum tribometer under different normal loads and sliding speeds at 8×10-5 Pa. The friction coefficient of the film decreases slowly with the increase of sliding rate, and the wear rate of the film gradually stabilized after running-in stage. With the increase of normal load, the friction coefficient of the film increases approximately parabolically, and the variation range is at the range of 0.03~0.24, and the wear scar width of the film surfaces also increases with the increase of load correspondingly.
    Effects of PTFE on Tribological Properties of Steel-backed UHMWPE Fiber Fabric Composites
    LIN Yudong, GUO Zhiwei, YUAN Chengqing,
    2022, 33(12):  1484-1492,1503.  DOI: 10.3969/j.issn.1004-132X.2022.12.010
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    In order to improve the tribological properties of the composite under the oil-free or grease lubricating environments of ships, the PTFE was combined with the steel-backed UHMWPE  fabric composite according to different mass fractions. The tribological characteristics of composites countered with 45 steel discs were studied under various rotating speeds in dry friction conditions. The friction coefficient and the wear rate were recorded. The surface profiler, scanning electron microscope and super deep scene microscope were used to observe and analyze the wear surface morphology of the composites and the counterparts. Research results show that the tribological properties of all PTFE-filled composites are better. With the increase of PTFE contents, the tribological properties of the composites decrease. Among them, the 1%  mass fraction PTFE-filled composites are the best, while under the test conditions the abrasive wear mainly occurs; Composites with higher PTFE contents mainly experience adhesive wear and fatigue wear at high speeds due to agglomeration and frictional heat accumulation. 
    Association between Wear Resistance of TiVN Coatings and Their Cutting Performance
    FAN Qingbo, YANG Fan, GUAN Xiaoyan, LI Hao, FAN Xiaoqiang, ZHU Minhao
    2022, 33(12):  1493-1503.  DOI: 10.3969/j.issn.1004-132X.2022.12.011
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    TiN and TiVN coatings were prepared by multi-arc ion deposition technology, and the tribological and cutting performance of the coatings at different conditions were compared, then the main factors affecting the service performance of tool coatings were pointed out. The experimental results show that V doping may effectively improve the hardness and bonding forces of TiN coatings, and reduce the friction factor and wear rate of TiN coatings at low temperature. However, the TiVN coatings have a higher wear rate when the temperature is higher than 500 ℃, and this is ascribed to the easy oxidation of V. The cutting tests show that TiN and TiVN coatings flake easily on the main cutting edges and transverse edge areas of the twist drills, whilst, there is no significant peeling of the coatings on flank surfaces of the cutting tools. It is supposed that the excellent cutting performance of TiVN coatings is ascribed to the high bonding strength and wear resistance. The service performance of the tool coatings is related to the wear resistance and bonding strength. In addition, the main cutting edges and chisel edge areas of the tools have strict requirements on the wear resistance and bonding strength. Meanwhile, the temperature of the cutting edge tips is high, which shows a high requirement for  high temperature wear resistances and bonding strength of the coatings.
    Response Behavior of Wheel-rail Interface Adhesion and Damage after Wheels Encountering Warm and Humid Airflow during Trains through Tunnels in Frigid Regions
    SHEN Mingxue, LI Shengxin, YU Meng, HUANGFU Lizhi, RONG Bin, XIONG Guangyao
    2022, 33(12):  1504-1511.  DOI: 10.3969/j.issn.1004-132X.2022.12.012
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    The response behavior of warm and humid airflows with different humidity(10% to 99%) on the adhesion of high-speed wheel-rail interfaces and wheel surface damages were studied by using a wheel-rail rolling testing machine under the environmental condition of -40 ℃. The results show that the adhesion coefficient will drop rapidly when the wheel-rail interfaces encounter warm and humid airflows in a low temperature environment, and with the increase of air humidity, the decrease amplitudes and the recovery time of the adhesion coefficient increase. Compared with wheel materials that are not exposed to warm and wet, the adhesion coefficient, wear amount, and plastic deformation layer thickness all increase significantly. With the increase of airflow humidity, the average adhesion coefficient decreases, and the wear amount and the thickness of the plastic deformation layer increase. Under the condition of low temperature and no moisture, the main form of wheel material wear is fatigue wear, and the section cracks are mainly surface cracks. Under the action of low-temperature intermittent warm and humid air currents, the main forms of wheel material wear are oxidative wear and adhesive wear. The third body layers formed by the accumulation of wear debris appear, and the section cracks appear multi-layer cracks and subsurface cracks. The warm and humid airflow has a significant effect on the adhesion of the trains wheel-rail interfaces and wheel damages in the low temperature environment. It is mainly reflected in the instantaneous drop in the adhesion coefficient and the more serious wear and fatigue damages of the wheel materials. Therefore, in order to ensure safer and more stable operation when trains pass through hot and humid tunnels in high-cold areas, special attention should be paid to the impact of warm and humid airflow on train wheels and rails.