Vol 59, No 9-10 (2018)

The effect of the content of carbon and niobium on the kinetics of the phase transformations of austenite and on the mechanical properties of the matrix metal and of the weld-affected zone is studied. The differences in the kinetics of the austenite transformations under post-rolling cooling of sheets and under the heat effect of welding on the matrix metal are shown.

The mechanical properties, the microstructure, and the cold resistance of coiled strips from low-carbon manganese-and silicon-alloyed steels with different additions of niobium and titanium produced by direct rolling of thin slabs right after their continuous casting under the conditions of foundry-rolling works are studied. It is shown that the addition of 0.01% Ti into the steel alloyed with 0.04% niobium has a positive effect on the ductility, toughness and cold resistance of the rolled strips and a negative effect on the strength. A high (0.08%) content of niobium is favorable for the impact toughness and resistance to brittle fracture of Charpy specimens of the steels studied under negative temperatures of up to –80°C.

The impact toughness and the structure of high-chromium martensitic steels with different tungsten contents are studied after tempering at 300 – 800°C. It is shown that when the tungsten content is increased from 2 to 3%, the temperature range of the irreversible temper embrittlement is widened and the impact toughness is decreased by a factor of 4.

The endurance of bearing steel ShKh15SG under cyclic bending tests is studied. The relation between the cyclic bending frequency and the ultimate bending strength is determined. It is shown that the endurance calculated by the prototype method does not match the results of full-scale tests of bearings. A new method for determining the endurance of bearings from steel ShKh15SG allowing for the distribution of nonmetallic inclusions in the carbide bands and outside them is suggested.

Computer simulation of the kinetics of thermal processes and structural and phase transformations in the wall of a bogie side frame produced from steel 20GL is performed with allowance for the differences in the cooling intensity under volume-surface hardening. The simulation is based on the developed method employing the diagram of decomposition of austenite at different cooling rates. The data obtained are used to make conclusion on the effect of the cooling intensity on propagation of martensite structure over the wall section.

The critical points of steel 75Kh3MF and the temperature of the start of martensitic transformation are determined by a dilatometric method. The thermokinetic and isothermal diagrams of decomposition of supercooled austenite are plotted. The microstructure and microhardness of steel specimens cooled at different rates are studied. The kinetics of the occurrence of bainitic transformation in the steel is calculated using the Austin–Ricket equation.

The microstructure of coatings deposited under radiation heating in vacuum at different parameters of pulsed glow discharge is studied. It is shown that depending on the length of the pulses of the glow discharge the deposited coatings may have alternating different-thickness chromium carbide layers.

The structure and the mechanical and operating properties of interlocks of NRQ drill pipes hardened by HFC treatment and carbonitriding are studied. The endurance characteristics and the wear and fatigue resistances of threaded joints of drill pipes of domestic and foreign producers are shown to differ and to depend primarily on the methods of surface hardening.

Failure of a logging wire under operating loads and corrosive hydrogen sulfide containing environments is considered. Metallographic studies in the region of flaws in the metal of the logging wire are performed. The stress-strain state of the metal is analyzed and mechanical tests are performed. Typical cases of damage of the logging wire are analyzed for determining the main factors lowering its operating capacity and for recommending ways for raising the reliability of logging wires.

The process of finishing plasma hardening with deposition of a multilayer amorphous coating of the Si – O – C – N system is considered as applied to hardening of the friction surfaces of spherical sliding bearings. The microrelief, the submicrorelief, and the tribological characteristics of the deposited wear-resistant antifriction amorphous coating, which are responsible for the elevated wear resistance of spherical sliding bearings, are investigated.

The effect of nanostructuring on the strength and fracture mechanism of materials possessing different crystal lattices is analyzed on the basis of available reports and experimental data of the authors. The structure, the hardness, the crack resistance, and the strength and ductility characteristics of steel 10 (bcc lattice), aluminum alloy AK4-1 (fcc lattice), austenitic steel AISI 321 (fcc lattice) are studied after equal channel angular pressing (ECAP) and those of Grade 4 titanium (hcp lattice) are studied after a ECAP-conform process (ECAP-C). It is shown that the ultrafine-grained (UFG) structure produced by the ECAP affects ambiguously the static crack resistance of the materials studied. The type of the crystal lattice influences substantially the temperature behavior of the impact toughness of the studied materials with UFG structure.

The effect of heat treatment parameters on the properties and structural and phase composition of a promising die steel 70Kh3G2FTR for hot deformation is studied. The temperature-and-stress state of a hammer die under a heat treatment is simulated.

Welded joints of medium-alloy steels XJY750 and 40KhN2MA are studied in the initial condition and after different variants of annealing. Special features of the phase transformations occurring in the welded steels are determined. Optimum modes of annealing are recommended for the studied welded joints of drill pipes, which provide a high level of mechanical properties including the case of impact loading.

The methods of optical and scanning electron microscopy are used to study the structure and phase composition of nitrocarburized layer in medium-carbon steels alloyed with manganese, chromium and nickel. Transmission electron microscopy is applied to study the structure of the heterophase zone and to determine its phase composition. The wear resistance and the wear mechanism of steels of different alloying systems are determined.

The effect of hydrogen sulfide containing environments, stress-strain states, stress concentration and external actions on the hydrogen sulfide cracking of steels is considered. Examples of typical and atypical action of hydrogen sulfide containing environments on carbon and stainless steels are presented. The factors responsible for hydrogen sulfide cracking are determined. Recommendations are given on design and production of equipment contacting hydrogen sulfide environments.