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It is established that intercrystallite corrosion of cutting-ceramic inserts arises when the chromium content in the peripheral zone of the grains is depleted by the deposition of chromium carbides at the grain boundaries, in the presence of stress due to the fast cooling of the inserts from high temperatures. This is especially apparent when 12Kh18N10Т, 40Kh13, 14Kh17N2, and other steels that are hard to machine are worked by a tool equipped with inserts of VOK-60M modified cutting ceramic. Research shows that the intercrystallite corrosion of cutting-ceramic inserts may be attributed to the stress arising in the surface layers of the grains as a result of carbide or nitride deposition. Heating cutting-ceramic inserts at 650–800°С lowers this stress and restores their resistance to intercrystallite corrosion. Research also shows that chromomanganese cutting-ceramic inserts are less susceptible to intercrystallite corrosion than are chromium–manganese–nickel inserts, while chromium–manganese–nickel cutting-ceramic inserts are less susceptible than are chromonickel inserts. The benefits of chromium–manganese–nickel cutting-ceramic inserts are especially pronounced with relatively brief machining of 12Kh18N10Т, 40Kh13, 14Kh17N2, and other such steels, in rigorous conditions, with a temperature of 600–650°С in the workpiece–tool contact zone. A new theory of the intercrystallite corrosion of VOK-60M modified cutting ceramic is based on the role of the kinetic factor at the relatively low tempering temperatures associated with the deposition of metastable carbide, although this does not lead to maximum change in free energy of the system but only to a relative change. In the cutting ceramic, this carbide may be chromium carbide (Cr, Тi)23C6, which is greatly enriched with titanium. With increase in tempering temperature, the deposited carbide tends toward the stable composition Cr23С6. Prolonged holding at the tempering temperature also tends to favor thermodynamic equilibrium. In other word, the chromium carbide is gradually enriched to reach the stable composition Cr23С6. This process is more rapid at higher temperatures. Obviously, the variation in composition of the carbide deposited at the grain boundaries in VOK-60M cutting ceramic with change in temperature and holding time will affect the kinetics of electrochemical solution of the system consisting of the carbide in contact with a solid solution. Research shows that vacuum sintering and annealing markedly improve the thermal stability. For the cutting ceramic, this is explained not only by the removal of fusible impurities but also by the larger quantity of aluminum and other alloying elements that remain in the strengthening phase, rather than being bound in oxides. Sintering in vacuum ensures greater plasticity of cutting ceramic based on nickel and cobalt in cutting 12Kh18N10Т and 14Kh17N2 steel at high speeds, with high temperatures in the machining zone. In addition, on sintering in vacuum furnaces, the content of small nonmetallic inclusions in the basic structure is 5–7 times less than in regular cutting ceramic. That significantly improves the deformability of the ceramic inserts. [ABSTRACT FROM AUTHOR]

Currently, critical components and assemblies made of traditional materials do not always meet the increased requirements of designers and service conditions. One solution to this problem is the development and application of dispersion-strengthened metal matrix composites. According to the informational–analytical review, a new fabrication technology of aluminum-based dispersion-strengthened composite material is presented. The peculiarities of this technology are described and sample macro- and microstructures, as well as mechanical characteristics of as-cast samples, are presented. The synthesis of strengthening particles immediately in the melt makes it possible to fabricate composites in one stage and provide thermodynamic stability, dense contact, and good adhesion between the matrix and strengthening phase. The particle sizes of the solid phase are in a range from 3 μm to 2 mm. The structural-and-phase state of the produced material is studied using optical metallography and X-ray diffraction analysis (a DRON-2 diffractometer). The microstructure is studied using a Keyence VHX-1000 microscope. The sample hardness is determined using a TKS-1M device, microhardness is determined using PMT-3 and HMV Shimadzu devices, ultimate strength is determined using ZD 10/90 and UME-10TM universal tensile testers, and impact strength is determined using an MK-30a pendulum impact tester. It is found that the variation in size and content of the strengthening phase makes it possible to vary mechanical properties of cast metal in a wide range. The application of the proposed technology will substantially decrease temporal and economical costs. A decrease in the fabrication cost of the dispersion-strengthened composite material is expected according to the results of the evaluative calculation. [ABSTRACT FROM AUTHOR]

Abstract—The intermetallic Ti3Al based alloys with the strengthening boride phases were obtained by the powder metallurgy methods; their composition, structure, and properties were studied. The optimum conditions for thermal treatment allowing obtaining the composite materials of the specified composition with the inclusions of the MAX phase were determined. [ABSTRACT FROM AUTHOR]

Features of the effect of alloying elements on linear thermal expansion coefficient of wrought heat-resistant alloys based on the Ni–Fe system are studied. Short-term and long-term strength at 600°C is simulated and parameters are used successfully as equivalent alloy chemical composition, calculated by a system of unpolarized ionic radii equations. A new deformable weldable alloy based on Ni–Fe–Co is developed with working temperature up to 650°C, with $ \upsigma_u^{20 } $ = 1400 MPa, $ \upsigma_u^{600 } $ = 1200 MPa, and $ \upsigma_{100}^{600 } $ = 950 MPa, with low linear thermal expansion coefficient (α = 11.8 · 10 –6 K –1 in the temperature range 20–600°C). The alloy is structurally stable, efficient in forming and welding, and with respect to set of properties it is better than standard alloys of similar designation. New alloy structure, phase composition, and properties are described. [ABSTRACT FROM AUTHOR]

The quality and durability of metallic materials is of considerable importance in many branches of industry, in particular, in metallurgy, engineering, and construction. This article gives the results of studying the effect of strengthening solid particles on structural heterogeneity, hardness, chemical composition and wear resistance of billets, prepared by centrifugal casting. [ABSTRACT FROM AUTHOR]