20 November 2020, Volume 44 Issue 11
    

  • Select all
    |
  • Effect of Carburizing on Microstructure and Tensile Properties of EthyleneCracking Furnace Tube after Service
    CHEN Weiqing, HAN Zhiyuan, WU Jianping, CAO Luowei, LIU Wenbin
    Materials For Mechanical Engineering. 2020, 44(11): 1-6. https://doi.org/10.11973/jxgccl202011001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Metallographic examination and tensile test were carried out on the long-term service radiation section tube of ethylene cracking furnace, and the microstructure, carbide size, room temperature and high temperature mechanical properties of carburized and non-carburized zone were studied. The quantitative relationship between carbide width and tensile properties of furnace tube was established. The results show that the grain morphology and size of non-carburized zone and carburized zone of the furnace tube were similar. The former was composed of austenite matrix, primary carbides, G phase and NbC phase; the latter had no G phase, and its primary carbides were obviously coarsened. The carburized zone had more creep holes and microcracks. The room temperature strength and plasticity of the furnace tube were seriously deteriorated. The high temperature tensile properties of the non-carburized zone basically met the requirements, and the carburized zone was obviously embrittled. The carbide width increased with the distance from outer surface of furnace tube. The tensile strength and yield strength of the furnace tube were positively related to the carbide width, and the percentage elongation after fracture was negatively related to it.
  • Damage Mechanism of GH4169 Alloy under Creep-Fatigue Interaction
    BAO Xiaoguang, WANG Runzi, WANG Ji, GUO Sujuan, ZHANG Xiancheng
    Materials For Mechanical Engineering. 2020, 44(11): 7-14,20. https://doi.org/10.11973/jxgccl202011002
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Damage characteristics such as cracks and pores on fracture and longitudinal slice of GH4169 alloy specimens were analyzed by scanning electron microscopy, after being tested under different creep-fatigue conditions (strain ratios of -1, 0, -∞; total strain ranges of 1.2%, 1.6%, 2.0%;tensile strain retention times of 60, 120, 300, 1 800, 5 400 s). The relationship between microscopic damage characteristics and experimental condition was explored. By electron backscatter diffraction technique, the initiation position and development process of the pores and cracks were qualitatively described, the creep damage was located and the damage mechanism of the alloy under the interaction of creep and fatigue was analyzed. The results show that the total strain range and the tensile strain retention time were inversely proportional to the specimen life, and were proportional to the crack source number and the number and size of cracks and pores on the longitudinal slice. The strain ratio had no significant effect on the specimen life. The creep damage accumulation of the specimen increased with the tensile strain retention time.
  • Compatibility of Structure Materials of Primary Loop in Reactor and Decontamination Solution
    ZHAO Yuxiang, KANG Wu, WU Fangyun, WEN Jie, PANG Peng
    Materials For Mechanical Engineering. 2020, 44(11): 15-20. https://doi.org/10.11973/jxgccl202011003
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Five reactor primary loop structural materials were subjected to immersion corrosion test by three-step chemical decontamination method at 95 ℃. The electrochemical performance of the materials in the decontamination solution and the compatibility of both were studied, and oxide film was prefabricated on 06Cr18Ni11Ti austenitic stainless steel to verify the effect of the three-step chemical decontamination method. The results show that the corrosion rates of five materials all met the requirements, and the mass loss and corrosion rate of 0Cr17Ni4Cu4Nb martensitic stainless steel were significantly higher than those of 06Cr18Ni11Ti, 06Cr19Ni10N austenitic stainless steels and 00Cr30Ni59Fe10, 00Cr25Ni35AlTi nickel based alloys. The material corrosion was mainly caused by oxalic acid citrate solution. There was no pitting corrosion and intergranular corrosion among the five experimental materials after immersion test. The three-step chemical decontamination process had a good removal effect on the surface oxides of 06Cr18Ni11Ti austenitic stainless steel.
  • Leakage Causes of Fin Tube of Middle Pressure Evaporator for Heat Recovery Steam Generator of Gas-Steam Combined Cycle Unit
    WU Yue
    Materials For Mechanical Engineering. 2020, 44(11): 21-24,28. https://doi.org/10.11973/jxgccl202011004
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A fin tube of middle pressure evaporator for heat recovery steam generator of gas-steam combined cycle unit leaked during operation. Macroscopic appearance and microstructure observation, scanning electron microscope and energy spectrum analysis, phase analysis and laboratory scale dissolving test were used to analyze the leakage reasons. The results show that the structures under the leakage point and nearby corrosion product layer were normal. Local areas of some fin tubes had been severely corroded during the original manufacturing, forming the blister-like corrosion products, which cannot be removed by chemical pickling and dissolution. During the unit operation, the position was further corroded by oxygen and thinned, which eventually led to the leakage. It was suggested to strengthen the acceptance management of the fin tube of middle pressure evaporator, focusing on the original defects such as blister-like corrosion and scratches to prevent such leakage accidents from recurring.
  • Reason for Cracking of an Intercity Train Gearbox
    ZHAO Lijuan
    Materials For Mechanical Engineering. 2020, 44(11): 25-28. https://doi.org/10.11973/jxgccl202011005
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    An intercity train gearbox cracked, resulting in oil leakage. The failure reasons were analyzed by macroscopic inspection, chemical composition analysis, metallographic inspection, scanning electron microscopy and tensile test. The results show that the failure mode of the gearbox was stress corrosion cracking. The gearbox was rigidly suspended during assembly, causing internal stress at the corner position of the closing surface, which became the source of cracks. The service environment of the gearbox was humid and contained chloride ions, and the closing surface of the gearbox was at the casting riser position, whose microstructure had deteriorated and declined, which further promoted the initiation and expansion of cracks. It was recommended to improve the casting process, optimize the gearbox structure design and assembly gluing process to prevent such failures from reocurring.
  • Research Status on Powder Recycling of Metal Powder BedFusion Additive Manufacturing
    HE Yanli, LEI Liming, HOU Huipeng
    Materials For Mechanical Engineering. 2020, 44(11): 29-34. https://doi.org/10.11973/jxgccl202011006
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Powder bed fusion additive manufacturing technique can quickly form complex structural parts with high dimensional accuracy, and has received extensive attention in many fields. However, compared with traditional manufacturing methods, its cost is higher. The recycling of metal powder can effectively reduce manufacturing costs. Combined with the research progress on additive manufacturing metal powders, changes of the chemical properties, physical properties and parts properties of commonly used 316L stainless steel, Ti6Al4V alloy and IN718 alloy powders in the recycling process are summarized. On the basis of demand for additive manufacturing of civil aviation parts, several problems existing in metal powders recycling are analyzed, and solutions are proposed.
  • Applications of Laser Cladding Technique in Remanufacturing of Shaft Parts
    WANG Zhengqiang, LI Wenge, DU Xu, ZHAO Yuantao
    Materials For Mechanical Engineering. 2020, 44(11): 35-40. https://doi.org/10.11973/jxgccl202011007
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Shaft parts are prone to failing such as friction, wear, corrosion and fatigue during service, which seriously affect the normal operation of construction machinery equipment. Laser cladding technique, as a common technical means for repairing and remanufacturing shaft parts, can effectively extend service lives of parts. The application of laser cladding technique in the remanufacturing of shaft parts is summarized. The influence of laser cladding process parameters (laser power, cladding speed, overlap rate and powder feeding amount) and cladding material selection on the repairing performance of shaft parts and the auxiliary application of simulation software are focused on. The development trend of laser cladding remanufacturing technique is prospected.
  • Effect of Scanning Speed on Internal Defects and Mechanical Properties ofTi-6Al-4V Alloy Processed by Selective Laser Melting
    JIANG Xiyi, XIA Weilong, LOU Dianjun, REN Xuepeng, SHAO Shuai, LI Haoqing, LIU Shuyu, FANG Xiaoying
    Materials For Mechanical Engineering. 2020, 44(11): 41-45. https://doi.org/10.11973/jxgccl202011008
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Ti-6Al-4V alloy was prepared by selective laser melting (SLM) technique, and the effect of laser scanning speed (705, 805, 905, 1 005, 1 105 mm·s-1) on internal defects, microstructure and mechanical properties of the alloy was studied. The results show that the pore defects and the porosity of Ti-6Al-4V alloy formed by SLM increased with the scanning speed. The alloy microstructure was composed of needle-like α' martensite, and the scanning speed had little effect on the microstructure morphology. With the increase of laser scanning speed, the tensile strength, yield strength and microhardness of the alloy decreased, and the elongation did not change much. The tensile fracture form of the alloy was ductile fracture, and there were deeper tensile cracks and more unmelted particles and spheroidization in the fracture at higher scanning speed.
  • Research Progress and Prospects of Metal Powder Preparation Technique for Additive Manufacturing
    HE Jie, MA Shizhou, ZHANG Xinggao, GAI Xiqiang, CHEN Houhe, ZHANG Kaichuang
    Materials For Mechanical Engineering. 2020, 44(11): 46-52,58. https://doi.org/10.11973/jxgccl202011009
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Additive manufacturing is an important development direction of advanced manufacturing technique for metal parts, but the metal powder for additive manufacturing has some problems such as insufficient research and development, weak stability and incomplete standards, which seriously restrict its development. The basic principles of common spherical metal powder preparation techniques including centrifugal atomization method, two-stream atomization method and spheroidization method are summarized, and their advantages, disadvantages and development status are introduced. It is proposed that the development of domestic additive manufacturing powder preparation technique can start from two aspects. One is to carry out process and equipment improvement and standardization research on traditional methods, and build automated factories; the other is to strengthen the research on basic theories of powdering and explore new processes.
  • Analytical Solutions of Thermal Residual Stress and Deformation of 3D Printed Parts
    ZHANG Zhaoshen, SHU Xiaoping
    Materials For Mechanical Engineering. 2020, 44(11): 53-58. https://doi.org/10.11973/jxgccl202011010
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For the thermal residual stress and deformation phenomenon of 3D printing parts, two key factors of platform and dynamic cooling gradient were introduced, and the analytical expressions of thermal residual stress and deformation were established and verified by numerical examples. The results show that the calculation was consistent with the actual situation after introducing the platform and dynamic cooling gradient. The greater the difference between the platform temperature and the forming temperature, the greater the cooling gradient, the thermal residual stress and the deformation. The platform removal time after printing had no effect on the thermal residual stress and deformation level, but ignoring the influence of the platform caused a large error in the analytical solution. Keeping the platform at a constant temperature significantly reduced the thermal residual stress, and the closer the holding temperature to the printing temperature, the lower the thermal residual stress.
  • Laser Cladding Process of Flow Channel in 316L Stainless SteelBipolar Plate for Fuel Cells
    XIAO Gang, LI Shichun, XIE Zhiyi, HUANG Guandi, ZHAN Zhuangchao, QUAN Sichang
    Materials For Mechanical Engineering. 2020, 44(11): 59-65. https://doi.org/10.11973/jxgccl202011011
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The 316L stainless steel bipolar plate for fuel cells was prepared by laser cladding forming process. According to the requirements of bipolar plate channel structure, the quantitative scoring standard of cladding channel was established. The effects of laser power, scanning speed and powder thickness on formability and corrosion resistance of the cladding channel were studied by orthogonal experiment. The results show that the effect of spreading powder thickness, laser power, and scanning speed on the formation of cladding channels decreased in order. The relatively low laser power, high scanning speed, small spreading thickness and low heat input were conducive to obtaining a cladding channel with better formability. Increasing laser power and scanning speed were both beneficial to improve the pitting corrosion resistance of the cladding channel. The better the formability of the cladding channel, the better the pitting corrosion resistance.
  • Effect of Solid Solution and Aging Treatment on Microstructure and Hardness of Selective Laser Melting GTD222 Nickel-Based Alloy
    PAN Weitao, ZHU Guoliang, WANG Rui, WANG Donghong, DONG Anping, SHU Da, SUN Baode
    Materials For Mechanical Engineering. 2020, 44(11): 66-71. https://doi.org/10.11973/jxgccl202011012
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The GTD222 nickel-based alloy was prepared by selective laser melting technique and then treated by solution at 1 150 ℃ and aging. The effects of solution treatment time (0,20,40,60,120 min), aging temperature (760,780,800,820,840 ℃) and aging time (2,4,8 h) on the microstructure and hardness of the alloy were studied. The results show that the columnar crystals in the GTD222 alloy formed by selective laser melting had a certain oblique angle to the forming direction. There were cellular substructures and high-density dislocations in the alloy, no γ' phase was precipitated, and MC carbides mainly distributed at grain boundaries and interfaces of adjacent substructures. The substructures of the alloy disappeared after solution treatment at 1 150 ℃. With increasing solution time, the carbides gradually dissolved, and the alloy hardness decreased first and then became stable. After aging at 760-840 ℃ for 2-8 h, a large number of γ' phases were precipitated in the alloy matrix. The size of γ' phase increased with aging time and temperature, while the hardness of alloy increased with increasing aging time and decreasing aging temperature.
  • Ultrahigh Cycle Fatigue Performance of GH4169 Alloy by Selective Laser Melting
    SONG Zongxian, WANG Dongpo, WU Zhisheng, SUN Ke, WU Han, LIU Xinming
    Materials For Mechanical Engineering. 2020, 44(11): 72-77. https://doi.org/10.11973/jxgccl202011013
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Tensile test and high/ultrahigh cycle fatigue tests with 105-109 cycles were carried out on selective laser melting (SLM) formed GH4169 alloy; the alloy was heat treated standardly. The tensile properties, fatigue properties and fracture morphology were studied, and the fatigue fracture mechanism was analyzed. The results show that after heat treatment, the tensile strength and yield strength of SLM formed GH4169 alloy were higher than those of forgings, but the elongation was greatly reduced, and the elastic modulus was slightly reduced. The S-N curve of SLM formed GH4169 alloy presented a stepped shape, showing inflection points near the 4×105 cycles and 5×107 cycles. The cracks of specimens in the high-cycle fatigue interval of 105-107 cycles all originated on the surface, while those in the ultrahigh cycle fatigue life interval exceeding 107 cycles were mostly generated inside. The internal crack source was the circular keyhole produced by the high laser energy density, and the residual carbide in the hole accelerated the crack initiation and reduced the fatigue life.
  • Prediction of Single Weld Bead Size of TIG Welding Arc Additive Manufacturing
    ZHAO Peng, Lü Yanming, ZHOU Wenjun, PAN Yu, BAI Shaoyun
    Materials For Mechanical Engineering. 2020, 44(11): 78-82,91. https://doi.org/10.11973/jxgccl202011014
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Orthogonal test of GH4169 nickel-based superalloy was carried out with the tungsten inert gas (TIG) welding arc additive manufacturing platform. Effects of welding current, welding speed, and wire feeding speed on weld width and reinforcement were studied. BP artificial neural network was established and optimized by genetic algorithm, the single weld bead shape and size prediction model was obtained, and a human interactive interface for size prediction was created by the graphical user interface (GUI) module of MATLAB. The results show that the weld width increased with the welding current, decreased with increasing welding speed, and first increased and then decreased with increasing wire feeding speed. The weld bead reinforcement was linearly positively correlated with the wire feeding speed, and negatively correlated with welding current and welding speed. The prediction relative error of the weld bead size prediction model was within 6%, which could predict the shape and size of a single weld bead more accurately.
  • Preparation and Performance of GNPs-MWCNT Conductive PolymerComposite Materials by Direct Writing 3D Printing
    CHEN Xiaojun, HU Cuiwen, CUI Ziyi, MO Deyun, LIAN Haishan, JIANG Shuzhen, GONG Manfeng, LUO Yihui
    Materials For Mechanical Engineering. 2020, 44(11): 83-91. https://doi.org/10.11973/jxgccl202011015
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Composite films with graphene nanosheets (GNPs) and multi-walled carbon nanotubes (MWCNT) as conductive fillers and polyethylene oxide (PEO) polymer as matrix were prepared. The effects of different filling content and ratios of GNPs/MWCNT on morphology, light transmittance, electrical conductivity and piezoresistive properties of composite film were studied. The results show that with the increase of GNPs/MWCNT filling content, the PEO polymer on composite material surface decreased, and the connectivity of conductive fillers increased. The light transmittance of composite material was reduced to below 50% after filling with GNPs/MWCNT, and the change of filler mass fraction and ratio had little effect on the light transmittance. The electrical conductivity of composite material was significantly improved with the increase of GNPs/MWCNT filling content and ratio. The composite material showed the best pressure-sensitive performance when the GNPs/MWCNT filling mass fraction was 10% and the mass ratio was 1:1, and the test precursor solution had good stability, excellent continuous printing ability, and could be used for large-area printing.
  • Effect of Ceramic Shot Peening on Fatigue Properties of TC18 TitaniumAlloy by Laser Additive Manufacturing
    FENG Kangtun, ZHAI Jiayou, YANG Kai, ZHANG Pingze, GAO Di
    Materials For Mechanical Engineering. 2020, 44(11): 92-96,101. https://doi.org/10.11973/jxgccl202011016
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Ceramic shot peening was performed on TC18 titanium alloy formed by laser additive manufacturing, and effects of shot peening intensity on the surface morphology, surface roughness, surface residual compressive stress, hardness and fatigue properties were studied. The results show that with the increase of shot peening intensity, the alloy surface processing traces gradually disappeared, but the craters became obvious, and the surface roughness and residual compressive stress increased. Shot peening improved the hardness and elastic modulus of the alloy. As the shot peening intensity increased, the fatigue life of the alloy increased first and then decreased, and the fatigue cracks source first transferred to the inside from the surface of the material and then returned to the surface. The fatigue life of the sample with 0.20-0.25 mm shot peening intensity was the highest.
  • Feasibility and Mechanical Properties of Ultra-thin Aluminum Alloy Sheet Prepared by Selective Laser Melting
    LIU Zhengwu, SHI Yun, WANG Yi, HAO Yunbo, CUI Yutao, ZHU Xiaogang
    Materials For Mechanical Engineering. 2020, 44(11): 97-101. https://doi.org/10.11973/jxgccl202011017
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    AlSi10Mg aluminum alloy thin sheets with thickness of 0.1-0.8 mm and hollow sheets with inner cavity gap of 0.5 mm were prepared by selective laser melting (SLM) technique. The feasibility of thin-walled structure SLM forming and mechanical properties of the formed parts were studied. The results show that the SLM technique could form thin sheets with wall thickness of more than 0.2 mm and hollow sheets with a cavity gap of 0.5 mm, but there was a hollow in the sheets with thickness of 0.5, 0.6 mm. The precision of SLM formed sheets was further improved by reducing the spot size and adjusting the contour process parameters, and the hollow thin sheet was avoided. The tensile strength of SLM formed and T6 heat-treated thin sheets were both over 200 MPa, and the specimen with thickness of 0.7 mm showed better mechanical properties. Adopting the test SLM process parameters could print thin-walled, closed-cavity radiator products successfully.
  • Effect of Pressure Infiltration on Properties of 3D Printed Al2O3 Ceramics
    PEI Wei, CAO Shu, YU Jinghu
    Materials For Mechanical Engineering. 2020, 44(11): 102-105. https://doi.org/10.11973/jxgccl202011018
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The pre-sintered 3D printed Al2O3 green body was subjected to pressure infiltration treatment with Al2O3 slurry, and then sintered. The effects of infiltration pressure and solid content of infiltration slurry on the relative density and compressive properties of ceramics were studied. The results show that the pressure infiltration significantly improved the relative density of 3D printed ceramics, and the greater the infiltration pressure, the greater the relative density of the green body. The relative density of the ceramic sintered samples with diameters of 1.0 cm and 1.5 cm gradually increased with the infiltrated slurry solid content, and the relative density of the ceramic sintered samples with a diameter of 2.0 cm increased first and then decreased. The infiltrating slurry with relatively low solid content was more helpful to increase the relative density of ceramic sintered samples with relatively large diameters, and the slurry with relatively high solid content was more suitable for ceramic samples with relatively small diameters. The bending strength of the 3D printed ceramics after infiltration was more than 10 times higher than that of uninfiltrated ceramics. As the solid content of the slurry increased, the bending strength of ceramic samples increased first. When the solid content (volume fraction) of the slurry reached more than 40%, the bending strength no longer changed significantly.
  • Flatness Change of Titanium Alloy Thin-Walled Parts by Laser Cladding and Milling Remanufacturing
    YU Fen, ZHANG Jin, WANG Ning, WANG Tao
    Materials For Mechanical Engineering. 2020, 44(11): 106-110. https://doi.org/10.11973/jxgccl202011019
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Laser cladding and milling remanufacturing of TC4 alloy thin-walled parts was carried out, and the influence of cladding trajectory (0°, 45° and 90°) and subsequent milling on the flatness of thin-walled parts was studied by using MATLAB software to fit the test data. The results show that after laser cladding with 0°, 45° and 90° cladding trajectories, the flatness of TC4 alloy thin-walled parts was improved comparing with that before cladding, and the flatness difference before and after cladding increased sequentially. The hardness of the TC4 alloy laser cladding layer was 20% higher than that of the matrix. After milling, the flatness of the thin-walled parts after laser cladding was further increased. The flatness of thin-walled parts with 90°, 45°, and 0° cladding trajectories decreased after milling, and the 0° cladding trajectory showed a better remanufacturing effect on titanium alloy thin-walled parts.
  • Effect of Solid Content on PLZT Ceramic Slarry Flowability in 3D Printing by Single Screw Extrusion Mode
    LI Bin, GU Hai, ZHANG Jie, JIANG Jie, SUN Jianhua
    Materials For Mechanical Engineering. 2020, 44(11): 111-114. https://doi.org/10.11973/jxgccl202011020
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For the 3D printing process of slurry direct writing ceramics with single screw extrusion structure, lead lanthanum zirconate titanate (PLZT) ceramic slurries with different solid content (60%, 70%, 75%, volume fraction) were prepared, and the effect of solid content on the slurry flow performance in screw groove was studied by MRT LBM method. The results show that the three ceramic slurries all showed obvious non-Newtonian fluid characteristics of shear thinning. MRT LBM method could effectively realize the flow simulation of ceramic slurries during 3D printing. With the increase of solid content, the slurry flow speed decreased. In the case of ensuring that the slurry rheology met the printing requirements, the solid content should not be too high.
Quarterly Established in 1978
Sponsor:
ShangHai Ship and Shipping Research Institute Co,.Ltd.
ISSN 1674-5949
CN 31-2023/U
　 Copyright © Materials For Mechanical Engineering, All Rights Reserved.
Powered by Beijing Magtech Co. Ltd,.