Russian Metallurgy (Metally)最新文献

Abstract—The problems of forming the structure of heterogeneous powder materials of tool plates are considered. A high-quality powder material is found to be produced as a result of creating a more equilibrium structure in the form of rounded solid-phase particles, which have a high adhesion strength with the minimum free (surface) energy of the interatomic interaction forces in the solid components of alloys. When a structure of powder alloys with regular-shape particles (faceted, rounded) is formed, the most important properties of hard alloys are found to increase, which eventually ensures such stable performance indicators of parts as wear resistance, fatigue strength, creep, and impact toughness.

Abstract—To reduce the losses of ferrosilicon during heavy-medium separation, it is necessary to increase its corrosion and mechanical resistance with the obligatory preservation of magnetic properties. To form ferrosilicon powder with the specified physical and mechanical characteristics that meet the technological process requirements, an automated heat treatment process control system is designed. The formed nitrided layer thickness is found to be controlled by the holding time and temperature. The total processing time is 3 h, and the temperature can vary in the range 900–1000°C. At higher temperatures, intense growth of silicon nitride crystals occurs.

Abstract—The efficiency of application of a new technology for repairing hydraulic distributors with the restoration and strengthening of the worn surfaces of the life-determining joints of parts and increasing their wear resistance is evaluated. The hydraulic distributors repaired according to the proposed technology exhibit an increase in the average overhaul life under real operation by 1.24 times compared to the life in the pre-repair period of operation.

Abstract—This paper presents experimental results on the machining of parts fabricated from powder materials. The specifics of porous surface structure formation in powder-metallurgy parts upon abrasive finishing are described.

Abstract—The effect of the main technological parameters of pendulum surface plastic deformation on the waviness parameters of cylindrical pieces has been considered. The experimental study has shown that pendulum surface plastic deformation significantly reduces the parameters of waviness (the height Wz and step Sw of waviness decrease by 30 and 50%, respectively). Using the Statistica 10.1 package, the measurement results have been processed to determine the optimal regimes of hardening ensuring the smallest parameters of waviness.

The effect of the vacuum ion–plasma treatment parameters on the regularities of nitride barrier coating formation on a VT23 titanium alloy (Ti–Al–V–Mo–Cr–Fe system) is studied. The resistance of the formed coating is studied upon subsequent vacuum annealing at 800°C for 1 h. The coating thickness is shown to increase with the titanium nitride deposition time. The formed nitride coating is found to have high resistance to heating in vacuum.

Abstract—For rolling of balls, one of the main parameters for both calculating passes and developing a model for a roll is the roll spacing at the crossing point (zones where the edges of the rolls are as close as possible to each other) in addition to the roll diameter, the roll body length, and the section length. A method is developed to calculate the roll spacing at the crossing point. The calculation results are used to analyze and choose rational tuning parameters of rolls for rolling balls at the EVRAZ NTMK ball-rolling mill. The analysis is carried out on new rolls and rolls after the first, second, third, and fourth remachining of screw ball-rolling grooves. The data are systematized to plot point curves for tuning indicators, and the graphical data are used to make a polynomial approximation. Equations are derived for the functions of the tuning parameters.

A new design of cutting tool for plastic recycling is proposed, and the use of a water–polymer ultrajet as a diagnostic tool for studying the functional properties of a material is considered. The experimental results demonstrate that the developed knife design has broad prospects for practical application. These results are confirmed by a comparative analysis of various diagnostic methods and strength calculations of the tool.

NiO nanoparticles are synthesized by vacuum arc sputtering. The effect of the synthesis parameters on the structural and magnetic properties of samples is studied. X-ray diffraction analysis confirms a polycrystalline structure of the nanoparticles prepared under all deposition conditions; however, the preferred orientation of crystallites depends on the deposition conditions. The magnetic behavior correlates with the crystallite size of NiO nanoparticles. Condensates with a particle size of 4–6 nm demonstrate superparamagnetic behavior, which changes into antiferromagnetic as the particle size increases.

The heat resistances of titanium, nickel, and carbon steel with aluminum-based coatings produced by liquid-phase aluminizing with diffusion annealing at 850 and 950°C are studied and compared. The influence of the holding time of aluminized titanium, nickel, and carbon steel specimens at 950°C on the changes in their weight and oxidation rate is revealed.