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Theme of master's degree work: "Study of microstructure of hard alloys by the methods of quantitative metallography"
При appearance of liquid phase there is the intensive growth of carbide corns, conditioned by the process of perekristallizatsii carbide through a liquid phase and accretion of neighbouring corns because of primary growth of one corn due to other. In the identical terms of spekaniya in alloys with more high maintenance of cobalt the middle diameter of corn is multiplied not only, but the quantity of large corns grows. Ivensen and Loseva marks that such tendency shows up especially distinctly, if powders of tungsten and carbide of tungsten with a not ravnovesnoy crystalline grate are used. The low (from technologically possible) temperatures of renewal of tungsten from oxides and karbidizatsii metal are the terms of receipt of such powders relatively. Substantial influence on growth of the WC corns in the WC alloys - With renders also the presence in the spekaemoy mixture of two-bit of other carbides. Small additions of carbides the IV and V groups to the WC alloys - With, as a rule, growth of the WC corns is braked, and is instrumental in the receipt of fine-grained alloys. The most effective influence on growth of corns is rendered by additions of carbide of vanadium. From data of the unpublished works Kreymera and employees, at addition a 0,1% VC koertsitivnaya force of alloy with 6% With increased to 300Э and higher, durability of alloys went down here. It is confirmed by the Alekseevoy work, that by the principal reason of appearance of large corns in the WC alloys - With there is the use of heterogeneous on granulometricheskomu composition powders of tungsten and carbide of tungsten, increase of duration and rise of temperature of spekaniya, especially in the case of alloys with more high maintenance of cobalt, made from fine-grained powders. Presently it is not the enough grounded data about negative influence of separate large corns on properties of alloys. However by works on research of character of distribution of cracks in the WC alloys - With it is shown, that large corns collapse quick, than shallow, and it is possible to suppose that the presence of large corns in alloys lowers their mechanical properties. It is possible that in the enriched by a cobalt areas of alloy the process of perekristallizatsii carbide of tungsten flows considerably more intensive, than in obednennih, that and conduces to the increased local growth of corns of carbide of tungsten. Other point of view is outspoken Novikovoy and taken to the following. At usadke in the process of spekaniya capillaries appearing between the particles of hard phase in the direction of less squeezing pressures, I.e. or to internal emptinesses - pores. In an enriched by a liquid area the process of perekristallizatsii and growth of corns increases that and leads a tungsten to appearance of accumulations of large corns of carbide.Research of microstructure of hard alloys is one of obligatory methods of control of quality of the prepared products let out by the factories of tverdosplavnoy industry. Unlike the tests of физико-mechanical and eksplutatsionnih properties of alloys the analysis of structure allows to judge not only about quality of alloys, but also about the lacks of the technological mode. The method of metallography control is selective and it is not always possible with a confidence to assert that one or two standards from party of the baked wares can reliably characterize quality of initial party of mixture and prepared products. However experience a lot of years showed satisfactory accordance between the results of control and operating properties.
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