PSI - Issue 40

Oleg N. Komarov et al. / Procedia Structural Integrity 40 (2022) 231–238 Oleg N. Komarov at al. / Structural Integrity Procedia 00 (2022) 000 – 000

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c d Fig. 4. Fracture patterns of the experimental samples obtained by means of aluminothermic remelting of thermites containing: a — 22% of the reductant and 10% of scheelite concentrate; b — 23% of the reductant; c — 23% of the reductant and 15% of scheelite concentrate; d — 23% of the reductant and 20% of scheelite concentrate. Fig. 4 shows the brittle nature of the fracture of the sample obtained from the composition containing 22% of the reductant and 10% of scheelite concentrate. The fracture of the sample obtained from the composition containing 23% of the reductant and no scheelite concentrate is of mixed nature (Fig. 4, b), while addition of 20% of scheelite concentrate results in clearly brittle fracture (Fig. 4, c). The fracture surface of the sample with the scheelite concentrate content of 15% (Fig. 4, c) features higher ductility as compared with the samples corresponding to the scheelite content of 20%. The fractures shown in Fig. 4, a, 4, c and 4, d have areas characterized by a dendritic structure. The pore sizes and their number, revealed visually at 2000 × magnification, are comparable to materials obtained by traditional methods of remelting and processing (rolling, forging, etc.). 5. Conclusions Experimental simulation of the process of production of a wear-resistant material by aluminothermic remelting of thermites has allowed for determining the influence of the reductant – scheelite concentrate quantitative ratio in such thermites on the chemical composition, structure, mechanical properties, and fracture pattern of the samples of a tungsten-containing iron-carbon cast product. It has been established that aluminothermy can be used as a means of obtaining a tungsten-rich alloy and blanks made of this alloy. Conditions have been determined for forming metal castings with no gas pores and with satisfactory mechanical characteristics. It has been established that the experimental alloy samples obtained by means of aluminothermic remelting of compositions with the reductant content of 23% have no gas pockets and feature stable hardness values falling within the range of 311 – 333 HB as well as the highest tensile strength values (up to σ w = 877 MPa). It has been found that addition of scheelite concentrate to such thermites enables reaching the tungsten content of up to 19.7% in the final products. Addition of 5 – 15% of scheelite to the thermites with the reductant content of 23% leads to ultimate tensile strength decrease within the range of σ w = 786 – 622 MPa. It has been established that the fracture of the samples is predominantly brittle in nature, which is due to high temperature gradient observed when casting the melt into the mold and as a consequence, the high cooling rate of