Vol 7, No 6 (2016)

Austenitic steel Kh20N6G11AM2BF with a nitrogen content of 0.4 wt % exhibits enhanced mechanical properties, high wear, and high resistance to stress-corrosion cracking (SCC) after quenching from rolling heating and after quenching from 1150°C and 15% cold deformation. This shows that it can be used in arctic shipbuilding as a cladding material for hull plates. Strong bonding of Kh20N6G11M2AFB austenitic steel cladding with a nitrogen content of 0.4 wt % with 10N3KhDMBF hull steel is obtained. The shear resistance is registered to be 437–520 MPa. Redistribution of the alloying elements with the formation of a martensitic layer, which is observed at the interface between the cladding layer and the base material, must be taken into account in the final heat treatment considering different processing conditions.

The paper studies single crystals of heat resistant intermetallide nickel-based alloy, microsegregation alloying elements within dendritic cells. The parameters of the lattices γ′ and γ phases are determined at room temperature by X-ray structural analysis. Alloying elements W, Cr, Mo and Co concentrate in the dendritic branches. It is shown that long-term (up to 690 h) creep tests in the temperature range of 1000–1200°C hardly change the phase composition of VIN3 alloy.

The experimental data on macrostructure, composition, and weight losses of unique KMU-4l carbon-fiber-reinforced plastic samples with surface modified by fiberglass fabric subjected to long-term exposure (12 years) in space environment as a part of Komplast 10-1 panels on the exterior surface of the functional cargo unit of the International Space Station are presented in the paper. Research results are obtained for the first time by methods of visual examination, gravimetric analysis, digital photography, optical microscopy, and energy-dispersion X-ray spectroscopy. It is shown that the studied macrostructural characteristics, mass loss, and elemental composition of modified carbon-fiber-reinforced plastic differ insignificantly for the reference and exposed test samples, i.e., the composite materials are characterized by stable macrostructural, physical, and chemical properties.

The paper presents a new method of creating composite powder materials for protective coatings. The article investigates the dependence of the properties of coatings on the ratio of matrix and reinforcement components in powder compositions. The properties of the coatings and their practical applications as innovative reinforcing materials are studied, as well as unique compositions based on the Ti/WC and Ti/TiCN systems.

The technology of long-measuring high-strength microwire casting in glass insulation of the intermetallic composition Bi₂Te₃–Sb₂Te₃ for thermoelectric devices is developed. Owing to physical and mechanical properties of microwires, there are good prospects for manufacturing high-strength thermocouples and thermoelectric modules.

The paper encloses results of experimental works on laser welding for evaluation of properties of welded joints of cold-resistant steels, applied for ship structures, working in Arctic conditions. Prospects on laser welding technology are given to incorporate new machinery based on fiber lasers, able to transport radiation by flexible optical cables.

Metallography reveals the correlations between the amount, size, and morphology of ultrafine particles in welding materials (flux-cored and composite wires, coated electrodes, and agglomerated fluxes), as well as the processes of formation of exogenous crystallization centers in the welding pool that facilitate the structure modification and promotion of processing and working properties of deposited metal. The phenomenological model of the nucleation on ultrafine exogenous refractory chemical clusters is developed on the basis of the experimental data and on the existing view of the kinetics of fast physicochemical processes in the welding fire point.

The paper presents results of comparative studies of corrosion resistance and corrosion-mechanical strength for low-magnetic shipbuilding steels of alloying systems Mn–C, C–Mn–Ni, Cr–Ni, Cr–Ni–Mo, and Cr–Ni–Mn–N, produced using various hardening mechanisms. It is shown that nitrogen-containing steels developed by CRISM Prometey constitute new constructional material superior in resistance to corrosion cracking in seawater compared with low-magnetic steels used in shipbuilding nowadays.

The paper considers test results for corrosion cracking in unfixed U-shaped samples of steels Cr18Ni10 and Cr18Ni8 in a 1 N HCl solution at a room temperature and in a saturated NH₄Cl solution at 100°C. It is found that, in such samples, corrosion cracks occur on both the convex and the concave side. This fact contradicts theoretical concepts according to which residual stresses of opposite signs have to occur in the surface layers on opposite sides of the samples after the bending and subsequent elastic unloading. Examples are presented for the formation of CC microcracks near the growing pittings in smooth flat samples made of steel Cr18Ni10Ti in the absence of external stresses.

The practice of the determination of cyclic crack resistance, i.e., the rate of fatigue crack growth depending on the range of the stress intensity factor, has existed for more than a decade. However, a number of problems related to the use of these data for the quantitative assessment of the service life for deep-sea equipment remain poorly understood. They are description of crack kinetics under alternating and mainly compressive loading cycles and taking into account the possible impact of differences in loading frequency for a sample and for a structure in corrosive media. The investigation of the impact of these factors is performed using a technique for monitoring the changes in the compliance of a sample, which allows one to register the loads of crack opening and complete closing and crack propagation at small temporal bases under testing with reduction of the frequency to 0.01 Hz.

Criteria of the safety assessment procedure are described with regard to pipelines of the FBR secondary loop. The short-term and long-term properties of strength and ductility, fracture toughness, creep rate, and creep crack growth rate within the temperature range of 550–800°C for steel 08Cr16Ni11Mo3 are given. The most probable scenario of sodium combustion is proposed. Results of the testing procedures in a straight section of the pipeline DN 900 with the sodium leakage via through cracks and its combustion on the external surface are presented. A diagram of the admissible states of the pipeline concerning the discharge of sodium is constructed.

A method that allows predicting the crack growth rate in austenitic steels under neutron irradiation creep is developed. A relation for prediction of the crack growth rate in the material of the VVER reactor internals is derived and its maximum value is assessed.