Browsing by Author "Wu, Hui"

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    Effects of holding time on the sintering of cemented tungsten carbide powder and bonding with high strength steel wire
    (Springer Link, 2019-07-15) Hasan, Mahadi; Zhao, Jingwei; Huang, Zhenyi; Wu, Hui; Jia, Fanghui; Jiang, Zhengyi
    Cemented tungsten carbide (WC-10Co) and high-strength (AISI 4340) steel were successfully bonded by hot compaction diffusion bonding at a low temperature. The effects of holding time (5-50 min) on microstructure and mechanical properties of the sintered carbides and bonding strengths of the dissimilar bilayered composite materials were examined. The results show that the mechanical properties of the carbides increase, but the bonding strength increases firstly and then decreases with the increase in holding time. The maximum density and hardness achieved are 95.92 and 99.5%, respectively. A transitional layer forms at the interface as a result of elemental interdiffusion. The depth of the layer increases with the increase in holding time. The optimal bonding time is determined to be 40 min at a temperature of 1200C and a pressure 160 MPa, by which the maximum bonding strength of 204 MPa of the WC-10Co/4340 steel joints can be achieved.
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    Influences of load and microstructure on tribocorrosion behaviour of high strength hull steel in saline solution
    (Springer, 2019-11-01) Wu, Hui; Li, Yan; Lu, Yao; Cheng, Xiawei; Hasan, Mahadi; Jiang, Zhengyi
    The tribocorrosion behaviour of two different hull steels (namely, EH36 and EH47) was investigated using a ball-on-disk tribometer under varying normal loads from 10 to 100 N in a 3.5 wt% NaCl saline solution. Sliding in pure water was also performed for a comparison purpose. The results indicate that the corrosion products mainly consist of lath lepidocrocite (γ-FeOOH) with residual NaCl crystals when sliding against both steels EH36 and EH47 in the saline solution. Tribocorrosion on EH36 (pearlitic steel) shows lower coefficient of friction (COF) values than those obtained in water, while tribocorrosion on EH47 (bainitic steel) leads to higher COF values instead. The former is due to the formation of considerable hydroxide particulates and films with small sizes. In contrast, the latter is ascribed to the ploughing of hydroxides with smaller amounts and bigger sizes. In particular, the synergistic effects of corrosion and wear in tribocorrosion result in much higher total materials degradation, compared to that obtained through pure mechanical wear in water.
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    Microstructural evaluation of WC and steel dissimilar bilayered composite obtained by spark plasma sintering
    (Springer, 2020-10-13) Hasan, Mahadi; Huang, Zhenyi; Zhao, Jingwei; Jumlat, Al; Jia, Fanghui; Wu, Hui; Jiang, Zhengyi
    Spark plasma sintering (SPS) is a powerful technique for consolidating metal powders at a remarkably shorter time with excellent quality. We used this technique for sintering nanocrystalline WC10Co powders and simultaneously bonding with high-strength steel. A series of experiments were conducted in order to find out the optimised set of SPS controlling parameters. The effects of temperatures (1000 to 1150 °C, with a 50 °C interval) in sintering nanocrystalline WC10Co powders and their bonding phenomena with AISI4340 steel were examined at a constant pressure of 80 MPa and a holding time of 5 min. The full density of the carbide powders was achieved at a lower temperature compared with that of conventional techniques. A number of techniques were employed to evaluate the microstructural characteristics of WC and steel bilayered composite and their mechanical properties. For determining the bonding strength of the joint, a novel micro-tensile testing system was adopted. Since such investigation is the first of its kind, to the best knowledge of the authors, where SPS is used to join the tungsten carbide with the steel, this research is expected to provide a valuable future reference for fabricating dissimilar bilayered composite materials.
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    Optimisation of sintering parameters for bonding nanocrystalline cemented tungsten carbide powder and solid high strength steel
    (Taylor & Francis, 2020-07-07) Hasan, Mahadi; Zhao, Jingwei; Jia, Fanghui; Wu, Hui; Ahmad, Farooq; Huang, Zhenyi; Wei, Dongbin; Ma, Lifeng; Jiang, Zhengyi
    In this study we examined the effects of compaction pressure for bonding nanocrystalline cemented tungsten carbide (WC-10Co) and high-strength steel (AISI4340) and successfully fabricated a bilayered composite of ceramic and steel. The obtained results were compared with our previous studies, and then the optimized sintering conditions were suggested. The compaction pressure examined varied from 120–200 MPa at 1150°C for 20 min. The study shows that the change in experimental parameters has significant effects on both the sintering properties of nanocrystalline WC-10Co powders and their bonding with AISI4340 steel. The microstructure reveals a successful metallurgical bonding between ceramic and steel. Bonding temperature determines, to a great extent, the diffusion processes across the bonding interface and has found to be the most influential variable compared to sintering time and compaction pressure. The obtained average maximum bonding strength of the bimetal composite is 226 MPa, which is higher than that of previous studies.