Metal Science and Heat Treatment

doi: 10.1007/BF01153863pmid: N/A

Lakhtin, Yu.

doi: 10.1007/BF01153864pmid: N/A

It is known that in order to obtain a high-hardness, wear- and corrosion-resistant article a nitrided layer of nitride ε(ε+γ′)-phases should be formed on its surface. However, in some cases, for example, in nitriding high-speed die steels and steel 38Kh2MYuA, the formation of brittle nitride surface layers should be eliminated and only a zone of internal nitriding (a+ γ′ + MN) should be formed in order to provide the requisite hardness and wear resistance. The article concerns preparation of nitrided layers with different compositions on the widely used 38Kh2MYuA nitralloy.

Ryzhov, N.; Smirnov, A.; Kirillov, K.; Semenov, M.

doi: 10.1007/BF01153865pmid: N/A

High-temperature cyanidation possesses a set of known advantages over carburization but the technological process is more difficult to control. In order to ensure the specified saturation of the diffusion layer both the carburizing and the nitriding capacities of the technological atmosphere are to be controlled precisely. The present article concerns a combined system for controlling cyanidation of low-alloyed steels in an ionized thermodynamically nonequilibrium gas medium, which includes an original method for diagnostics of the processes occurring both in the technological atmosphere and on the saturated surface.

Tikhonov, A.

doi: 10.1007/BF01153866pmid: N/A

In large-scale production, which the automobile industry is, the use of chemicothermal treatment (CTT) has special features. These are the variety of saturation processes (from low-temperature saturation in salts to high-temperature saturation in a controlled atmosphere), simultaneous saturation by carbon and nitrogen, use of continuous furnaces with a high capacity, the special requirements imposed on steels associated with the narrow range of variation of the chemical composition, the hardenability curves, and grain coarseness, the specific conditions for preparing the controlled atmosphere both in generators and in the functional space of the continuous furnaces, and the continuous development of optimum technologies for each group of parts.

Kogan, Ya.; Sereda, B.; Kostogorov, E.

doi: 10.1007/BF01153867pmid: N/A

An analysis of the reactions occurring in the combustion of an SHS powder mixture and results of experiments and metallographic investigations are used in considering the formation of strengthened layers.

Galin, R.; Voroshnin, A.

doi: 10.1007/BF01153868pmid: N/A

The powder mixtures used for diffusion galvanizing (Zn + inert filler + activator) have the following deficiencies: susceptibility to sintering and fusing under elevated CTT temperatures, complexity of correcting the set of components in repeated use of the mixtures and the related instability of the results obtained, complexity of regeneration of worked-out mixtures, elevated ecological hazard of their use, etc. This explains the need for the present work, which shows that most of the mentioned deficiencies can be eliminated by an appropriate choice of the mixture components and (or) preliminary treatment of them.

Meshkov, Yu.

doi: 10.1007/BF01153869pmid: N/A

It is shown that the spent part in the energy balance describing the loss of stability of a sharp atomic crack in the classical Griffith criterion for fracture of brittle bodies (glasses) should exceed the quantity 2y (y is the surface energy of the metal) adopted by Griffith by an order of magnitude and be equal to 20y. In fracture of a brittle body most of this energy is lost in the form of dissipated elastic waves (sound). In the case of a macrocrack the fraction of the dissipated energy is even higher and is proportional to the radius p of the tip of the crack.

Kremnev, L.

doi: 10.1007/BF01153870pmid: N/A

The critical coefficient of stress intensity in linear fracture mechanics and an analytical expression for evaluating it have been established for the conditions of absolutely brittle fracture in a continuous isotropic medium. At the same time, the resource of plasticity in actual discrete (crystalline) materials is often determined using the concept of fracture toughness (crack resistance) calculated by the same equation as that used for evaluating the critical stress intensity. The article concerns the causes and consequences of this phenomenon.

Tsybulina, I.; Tulyakova, G.; Uporova, V.

doi: 10.1007/BF01153871pmid: N/A

In Russia functional blades of low-pressure cylinders (LPC) are produced from single-phase titanium alloys. These blades do not meet the strict requirements currently imposed on their material because the length of the blades has increased. In foreign countries such blades are preferentially produced from a biphase Ti - 6% Al - 4% V alloy. This alloy possesses high adaptability to manufacturing and a good combination of mechanical properties and corrosion resistance. A domestic counterpart of the Ti - 6% Al - 4% V alloy is VT6. The present article is devoted to the possibility of its use for functional blades of LPC.

Moiseev, V.; Sysoeva, N.; Ermolova, M.

doi: 10.1007/BF01153872pmid: N/A

A standard regime of heat treatment has been developed for semifinished products of VT22 alloy manufactured by the conventional technology (casting + deformation). However, it gives a comparatively low level of crack resistance in the case of granular technology (hot isostatic pressing + deformation). In this connection it became necessary to refine the regime of heat treatment of the granulated VT22 alloy. The present work concerns the effect of different regimes of heat treatment on the size and shape of segregations of the ct-phase, investigated with the aim of improving the crack resistance characteristics of granulated VT22.