Titanium №4 2013
RAW MATERIALS. TITANIUM SPONGE
DEVELOPMENT OF PROCESSES OF OBTAINING METALLIC HAFNIUM BY ELECTROLYSIS OF CHLORIDE-FLUORIDE MELTS AND STUDY ITS PROPERTIES
V. Bezumov, A. Dunaev, A. Kabanov, V. Novikov, S. Kuznetsov
In Joint-Stock Company “VNIINM” the processes of obtaining metallic hafnium by electrolysis of chloride-fluoride melts were developed.
Comparative studies of molten salt systems HfCl4-NaCl-KCl and K2HfF6-NaCl-KCl-KF were carried out by cyclic voltammetry for the choice of electrolyte composition.
For the first time the electrolytic hafnium of required purity was obtained without iodide and electron-beam refining.
Keywords: molten salts, cyclic voltammetry, electrolysis, powder of hafnium.
RESEARCH OF WORKING CAPACITY CHARACTERISTICS OF HIGH-STRENGTH PSEUDO-ALPHA TITANIUM ALLOYS IN ENERGY-MACHINE BUILDING PRODUCTS
A. Oryshchenko, I. Kozlova, L. Ivanova, A. Kudryavtsev, E. Chudakov
There are researched characteristics of high-temperature strength and fatigue durability at elevated temperatures of deformed semi-finished products out of titanium pseudo-alpha alloys systems Ti-Al-Mo-V-C and Ti-Al-Mo-Zr-C, originally designed as marine materials. The influence of the type of structure on mechanical and working capacity characteristics is analyzed. The structure providing service characteristics in optimum complex at elevated temperatures is determined. The possibility of using pseudo-alpha titanium alloys systemsTi-Al-Mo-V-C and Ti-Al-Mo-Zr-C in heavy loaded elements of the energy equipment operated at temperatures up to 500oC is confirm.
Keywords: titanium pseudo-alpha alloys, characteristics of working capacity, structure, energymashine building.
THE STRUCTURE AND CHEMICAL HETEROGENEITY OF PRESS-WELDED CONNECTIONS OF BIPHASE HEAT-RESISTANT TITANIUM ALLOYS WITH DISPERSIVE HARDENING
T. Taranova, G. Grigorenko, S. Akhonin, O. Zadorozhnyuk, V. Sabokar’, T. Solomiychuk, E. Polovetsky
Both in the area of contact and in the basic metal intermetallic and silicide particles are found and their volume share, size and morphology are defined. Large congestions of silicides are formed at grain boundaries and block it and reduce plasticity. As a result of heat treatment large congestions of silicides at grain boundaries are reduced and coagulate. The heat treatment in the heat-resistant titanium alloys increases the structural homogeneity and the probability of formation of cracks goes down, that favorably affects the mechanical properties of weld joints.
Keywords: the heat-resistant titanium alloys, microstructure, dispersive hardening, silicide and intermetallic particles, press-welding, heat treatment.
REGULARITIES OF SUBMICRO- AND NANOCRYSTAL STRUCTURES FORMATION IN α- AND NEAR-α-TITANIUM ALLOYS AT THERMOHYDROGEN TREATMENT AND PLASTIC DEFORMATION
S. Skvortsova, A. Mamonov, М. Afonina, V. Zasypkin
Principal regularities are considered and mechanisms are described for submicro- and nanostructures formation in as-cast and deformed semi-products of VT20, VT18Y and VT5 titanium alloys at thermohydrogen treatment (THT) and at combination of TNT with plastic deformation. It was shown that the formation of these structures resulted from realization of interconnected physicochemical effects conditioned by peculiarities of hydrogen influence on phase and structural transformations in titanium alloys.
Keywords: titanium alloy, thermohydrogen treatment, phase transformation, submicrocrystal structure, nanostructure, hydrogen, plastic deformation.
Semi-products manufacturing technologies
PILOT HIGH-TEMPERATURE Ti2AlNb-BASE ALLOY PRODUCTION PROCESS DEVELOPMENT AND OPTIMIZATION
N. Nochovnaya, S. Skvortsova, D. Anishchyuk, E. Alexeev, P. Panin, O. Umarova
In the present article there have been disclosed the results of applied research project concerning a pilot high-temperature ortho-alloy Ti-13Al-40Nb-5(Zr+V+Mo+W)-0.5(Si+C) as well as technological aspects of ingots and hot-deformed disk workpieces production thereof. It has been shown that one should apply a threefold vacuum-arc remelting with 15–18 А/сm2 specific current in order to obtain a chemically homogeneous ingot. The conducted experiments have revealed that it is possible to obtain disk workpieces by means of simplified thermomechanical treatment (without strain exes variation). In this case the material possesses high strength (1200 MPa) and satisfactory ductility (2.5 percent). Furthermore, both technological plasticity increase and a fully uniform structure formation can be provided by hot deformation with multifold strain exes change.
Keywords: high-temperature ortho-alloy, vacuum-arc melting, current density, ingot, thermomechanical treatment, strain degree, deformed semi-finished product.
Semi-products treatment technologies
VT6 TITANIUM ALLOY NITRIDING
V. Fedirko, A. Ilyin, I. Pogreljuk, S. Skvortsova, A. Lukyanenko, T. Kravchishin
The regularities of the VT6 titanium alloy nitriding at 750–950°C, and the process duration to 10 hours was studied. The influence of temperature and duration of the nitriding process on characteristics of the surface and near-surface layer of the metal was shown. The kinetics of mass changes the samples, the phase composition of the surface layer was studied. The changes the surface roughness, surface micro hardness, the distributions of micro hardness and microstructure of the near surface layers was shown.
Keywords: titanium alloy, nitriding, structure, properties, surface.
BEHAVIOR OF PSEUDO-ALPHA TITANIUM ALLOYS IN STEAM TURBINE EQUIPMENT UNDER OVERLOADED CONDITIONS
V. Travin, V. Leonov, A. Kudriavtsev, L. Ivanova, V. Michulin
Designing of power equipment supposes, as a rule, its behavior under over calculated loaded conditions at a short time. For details and assemblies of steam turbine units, made by high strength weldable pseudo-alpha titanium alloys, it is necessary to calculate their specific conditions for saving serviceability. They are - character of deformity function under real stress condition, concentrator sensitivity, cyclic load resistance, creep and the other. Some examples of type-design turbine details behavior under overloaded conditions are considerate in this article. A suggestion for providing strength and carrier ability high loaded titanium elements of power machine building are formulated. In particular, author’s conclusion about realization of structure strength reserves by means of material plastic properties is confirmed.
Keywords: pseudo-alpha titanium alloys, power-machine equipment, overloaded conditions, strength reserves, plasticity.