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Luo C.,China North Industries Group Xian Huashan Tungsten Products Co. | Wang J.,China North Industries Group Xian Huashan Tungsten Products Co. | Sun G.,China North Industries Group Xian Huashan Tungsten Products Co. | Zheng J.,China North Industries Group Xian Huashan Tungsten Products Co.
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2016

Cylindrical 90W-Ni-Fe tungsten heavy alloys were prepared by means of powder metallurgy with the addition of 20 μm coarse tungsten powder. Sintering warpage was investigated through measuring and computing the major to minor axis ratio of oval intersecting surface. The tensile strength and elongation of alloys were tested with quasi-static tensile testing machine. Optical microscope (OM) and scanning electricity microscope (SEM) were used to characterize microstructure of alloys, respectively. The results indicate that sintering warpage significantly decreases with coarse tungsten powder additions, and the material charge amount can reduce to about 80% when producing cylindrical tungsten heavy alloys, the utilization ratio of materials increase obviously; When coarse tungsten powder addition is in the range of 70~90%, the tensile strength is about 950 MPa and and elongation is about 20%, respectively, compared with the alloys without coarse tungsten powder, the tensile strength increase by 30 MPa and the elongation reduces by 28.5%. The results are caused by transgranular fracture, low interface combination strength and non-uniform distribution of binding phase, etc; The tungsten crystal grains are irregularity with existence of the super large tungsten crystal grains. © 2016, University of Science and Technology Beijing. All right reserved.


Wang Z.,China North Industries Group Xian Huashan Tungsten Products Co. | Luo C.,China North Industries Group Xian Huashan Tungsten Products Co. | Xiao J.,China North Industries Group Xian Huashan Tungsten Products Co. | Zheng J.,China North Industries Group Xian Huashan Tungsten Products Co. | Peng Y.,China North Industries Group Xian Huashan Tungsten Products Co.
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2014

93W-Co-Ni tungsten heavy alloys with high hardness were prepared by compositing, cold isostatic pressing and sintering with m(Co):m(Ni) ratio of 6:1. The influence of sintering temperature on density and microstructure was investigated, the change of HRC hardness in sintering process was studied, and the cause of hardness increasing was analysed. The results show that with increasing sintering temperature, the density increases, the density reaches the value of 17.73 g·cm-3 and the relative density reaches 99.16% by sintering at 1605°C. With increasing sintering temperature, the tungsten crystal grains grow and get smooth, at last the average grain size is about 20.91 μm, which accords with sintering mechanism of powder metallurgy. In the sintering process, the HRC hardness of alloy first reduces and then tends to stabilization in the range of 41~42. The smaller tungsten crystal grains and formation of intermetallic phase Co7W6 result in the increase of hardness.

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