Yu. G. Veksler

Corrosion and cavitation-corrosion resistance of 95Kh18 steel

Conclusions1.In the active area of the anodic polarization curve the corrosion of 95Kh18 steel under static and cavitation conditions occurs with active solution of the martensite. In the passive area under static conditions strong passivation of the steel is observed and in cavitation a less resistant passive condition indicating dynamic equilibrium of the activation and passivation processes.2.The phase γ→α-transformation occurring in cavitation in 95Kh18 steel reduces some-what its corrosion resistance but significantly increases the total cavitation-corrosion resistance.3.The degree and character of the cavitation-corrosion failure of 95Kh18 steel hardened from different temperatures are determined by the degree of localization of plastic deformation. Coarse slip in the steel with stable austenite leads to greater erosion of the specimen and the formation of a more developed relief than for the steel with metastable austenite subjected to more uniform plastic deformation.4.The corrosion resistance of 95Kh18 steel in cavitation under conditions of the experiment conducted (5 M H3PO4 solution and a passivating polarization potential of 0.5 V) is determined primarily by the capacity for passivation. In this case the mechanicochemical effect obviously plays a lesser role.

Multicomponent Heat-Resistant Coatings for Blades Produced Using Ion-Plasma Method

It is shown that the ion-plasma method can be combined with the diffusion methods for the formation of complex heat- and corrosion-resistant coatings on blades of ЖC6У alloy. The complex method enables one to apply metal layers, for example, Ni–Cr–Zr, and to produce surface ceramic film based on fcc ZrO2. A version of the coating satisfied the imitative tests and, as a part of an article, the pilot-industrial tests.

Use of Low-Active Circulating-Gas Aluminizing for Repairing the Nozzle-Set Containers of a Turbine

The cause of damage in internal and external containers of the nozzle set of the first stage of the TV3-117 engine is shown to be the intercrystallite gas corrosion of the materials of which they are produced (alloy KhN38VT and steel 12Kh18N10T, respectively). It is shown that low-active circulating-gas aluminizing can be used for repairing the parts, increasing their high-temperature strength, and “curing” micro- and macrocracks.

Vibration-gas-abrasive wear resistance of turbine compressor blades

The scheme of gas-abrasive wear test of turbine compressor blades under free vibration of blades, including at high temperatures, is proposed. The amplitude- and time-dependences of the wear rate of εν961-steel and BT8-alloy blades, having either with or without a (Ti,Zr)N coating, were compared. The coatings effectiveness is almost the same for both cases at 20°C, but at 150°C, it is lower for steel blades because of spalling the coating due to its deficient adhesion.

Certain peculiarities of Zr−Cr−N coatings on steel blades of a gas-turbine engine compressor

The properties of compressor blades of a helicopter gas-turbine engine with an experimental ionplasma coating Zr−Cr−N, are compared to those with Ti−Zr−N basic composition. It is shown that, due to the structural properties, the experimental coatings make the blades more corrosion-resistant, and mitigate the dependence of their residual properties on the amplitude and the temperature of the preliminary vibrotempering.

Properties of diffusion alumino-zirconium coatings with microadditions

In the development of materials resistant to gas corrosion at high temperatures interest has been traditionally directed towards aluminum-containing coatings on a metallic substrate, with inert oxide films on the surface. Oxide layers based on cubic, tetragonal, or mono-clinic ZrO{sub 2} are examples of the latter. The methods of production include various processes for saturating the surface of a part with aluminum and zirconium (and possibly other elements) deposited simultaneously, or in sequence. In this work, specimens of nickel base coatings were used as substrates on which layers of diffusion coatings were deposited. 6 refs., 3 figs.

Structural transformations in heat-resistant protective coatings on nickel alloys

Conclusions1.Increase of atmosphere corrosivity and operating temperature for components with heat-resistant aluminide coatings leads to an increase in the role of phase instability in coating failure.2.Diffusion processes occuring during operation cause impoverishment of the β-phase (NiAl) of aluminosilicide coatings in alloying elements and its destabilisation.3.Aluminosilicide coatings on alloys with a high chromium content may be used effectively in a corrosive gas atmosphere with retention at temperatures which do not lead to martensitic transformation.4.Co−Cr−Al-Y coatings compared with Al−Si and Al−Nb−Si coatings have a greater stability and better corrosion resistance during operation in combustion products with a high sulfur content.

Influence of preliminary cold deformation on the cavitation-corrosion resistance of 12Kh18N9T steel

However, in practice as a rule parts operating in chemically active media are subjected to cavitation action. Austenitic steels, which possess low cavitation-corrosion resistance in comparison with martensitic steels close in composition, are normally used for service in such media [4]. In connection with this it was of interest to investigate the influence of deformation martenslte formed as the result of preliminary working and also of the ~ ÷ ~ phase transformation on the corrosion resistance of austenitic stainless steels under cavitation conditions.

Strain of metals exposed to cavitation

Conclusions1.The mechanical characteristics determined in accordance with standard practice do not reflect the ability of materials to withstand cavitation failure. The operating stability of a material can be correlated only with a set of characteristics determined on the basis of cavitation-mechanical tests.2.Cavitation action combined with uniaxial tensile loads reduces sharply the deformation stress and causes progressive elongation of the specimen without a marked increase in the effective stress due to the dynamic recovery phenomenon. The reduction in the deformation stress is proportional to the amount of strain and the intensity of cavitation action.3.Ultrasound irradiation of a metal specimen subjected to uniaxial tensile loading, in contrast to cavitation action, reduces only the strain hardening coefficient.

Study of short term creep in fast air flows, allowing for the variable loads arising from vibrations

Conclusions1.An increase in the air-flow velocity from M=0.94 to M=1.6 for the OT4 alloy at 500°C and from M=0.7 to M=1.6 for the VZh98 alloy at 1000°C accelerates creep and shortens the total time-to-failure as a result of an intensification of the corrosion-erosion action of the flow. The degree of deformation at the point of failure diminishes by a factor of 2 to 2.5 as compared with tests in still air.2.An increase in the angle of attack at a constant air-flow velocity (M=0.94) for these alloys accelerates the creep rate as a result of an increase in the average statistical value of the dynamic stress component.