The features of metal powders consolidation by layer-by-layer electric discharge sintering

Additive technologies (3D printing), i.e. layer-by-layer production of bulk materials from powder precursors, are very promising in the modern industry. These technologies make it possible to obtain products with complex geometric shapes and materials with a unique variety of properties. The range of products which can be obtained by 3D printing is extremely wide, therefore the search for new methods and techniques of 3D printing is of great current interest. This paper suggests a method of obtaining bulk materials of a complex shape from electroconductive powders based on the technology of spot electric discharge sintering. This method is a layer-by-layer consolidation of powders, where each layer is formed as a result of successive spot sintering of small amounts of powder compressed between the electrode and the substrate, or between the electrode and the previously sintered layer. It is shown that the method developed makes it possible to obtain bulk samples from powders with various chemical compositions (Cu, Ti, mechanically synthesized tin bronze), particles of various shapes (dendritic, dumbbell-, and stone-like), and of various structural-phase states. The structural-phase states and porosity of the obtained bulk materials were studied by the X-ray diffraction and electron microscopy. The powders sintered by the method are mostly affected by the heat release along the boundaries of the grains of the powder which, in its turn, depends on the electrical resistivity of the material and the structural-phase transformations in the process of consolidation. The porosity of the sintered samples mainly depends on the type of the powder used and decreases with the decrease in the size of the grains of the powder.