DOI: 10.18503/1995-2732-2021-19-2-79-89
Abstract
This paper shows that it is feasible to produce solid pressed bimetallic rings and other products with working layers of atomized powders of high-speed steels. It was found that the mechanical activation of atomized powders does not contribute to an increase in the density of compacts. Adding powders of ductile metals (nickel and copper) to the charge improves the formability, slightly increases the density and microhardness of the molding material. The authors determined the regularities of the structure formation of interlayer boundaries and working layers during sintering of solid pressed internal combustion engine valve seats. It was shown that the structure formation and diffusion mass transfer at the indicated boundaries were significantly influenced by the method of powder activation, the composition of the charge, the affinity of the components, the mode and conditions of sintering. Depending on the content of nickel and copper in the charge, microhardness of the transition zone varies from 2800 to 3200 MPa. The authors identified concentration curves of the distribution of components in the interlayer boundaries of bimetallic samples of different chemical compositions, and the values of the coefficients of mutual diffusion of Fe and Cr in the transition zone. It was found that after the combined introduction of copper and nickel powders, they activate the diffusion of iron and chromium in the transition zone by mutually dissolving during the sintering process. Alloying with nickel alone leads to the fact that it binds chromium, forming a solid solution of a complex composition. It was shown that the mechanical properties of sintered bimetallic specimens with a working layer based on atomized powders of high-speed steels substantially depended on the sintering conditions. After vacuum sintering ultimate strength and percentage elongation in the transition zone of the bimetallic specimens are significantly higher (by 1.5–2 times) compared to the specimens sintered in dissociated ammonia (DA).
Keywords
Atomized powder, activation, bimetallic seats, mutual diffusion, structure formation, mechanical properties.
For citation
Gasanov B.G., Babets A.V., Baev S.S. Producing Bimetallic Rings for Valve Seats of Internal Combustion Engines from Activated Powders of High-Speed Steel. Vestnik Magnitogorskogo Gosudarstvennogo Tekhnicheskogo Universiteta im. G.I. Nosova [Vestnik of Nosov Magnitogorsk State Technical University]. 2021, vol. 19, no. 2, pp. 79–89. https://doi.org/10.18503/1995-2732-2021-19-2-79-89
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