Abstract
Tungsten heavy alloys (THA) are used in the defense industry for subcaliber bullet cores due to their high density and strength. Typically methods of joining tungsten rod elements include: soldering, friction welding or threaded sleeve splicing. The properties of the joints were tested for three types of material containing 90.8, 96.2 and 98.2 wt.%. tungsten, density from 17.3 to 18.4 g/cm3 and strength range 400–1000 MPa. Combination in the liquid phase at the sintering temperature was carried out in a vacuum furnace at a temperature of 1520 °C in a hydrogen atmosphere, and tests used pairs of both identical and dissimilar materials. After that, some of the bars were subjected to additional heat treatment at 1100 °C for 3 h. The tests of the mechanical properties in the static tensile test and the measurement of impact strength showed that the obtained strength of the joints was comparable to that of the parent material. The microstructure analysis showed that the resulting joint area, while maintaining the appropriate roughness of the joined end faces of the bars, is homogeneous without areas of the solidified matrix of the joint line. Research showed that it is possible to bond under sintering conditions with the participation of a solid liquid phase of homonymous and dissimilar THA materials. The strength of joints in dissimilar materials was comparable to a tungsten heavy alloy material with lower strength in the bonded pair while homonymous materials were comparable to the original material. The test results provided a good basis for further research in which the obtained pairs of joints will be subjected to plastic working processes.
Highlights
IntroductionTungsten heavy alloys (THAs) are materials produced mostly by liquid phase sintering
Tungsten heavy alloys (THAs) are materials produced mostly by liquid phase sintering.The two-phase microstructure consisting of tungsten grains and a binder causes these materials to be referred to as tungsten composites [1,2,3,4]
Three tungsten heavy alloys marked as THA-1, THA-2 and THA-3 were prepared
Summary
Tungsten heavy alloys (THAs) are materials produced mostly by liquid phase sintering. The two-phase microstructure consisting of tungsten grains and a binder causes these materials to be referred to as tungsten composites [1,2,3,4]. The chemical composition of the matrix is a nickel solution with the addition of elements such as iron, cobalt or copper. Due to their characteristic properties such as high density, high strength, plasticity, and impact strength, are used, among others, for the production of radiation shields, balancing elements or sub-caliber bullet cores [5,6,7]. Attempts to produce THA were carried out to replace lead in the production of radiation shields. A breakthrough in the Materials 2020, 13, 4965 ; doi:10.3390/ma13214965 www.mdpi.com/journal/materials
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