Віктор Гаврилович Хижняк

DIFFUSION TITANIUM ALUMINIZING OF HEAT RESISTANT ALLOY ХН55ВМТКЮ IN THE CLOSED REACTIONARY SPACE

Issues. To prevent surface oxidation of high-temperature alloys is possible by using diffusion coatings, composed of layers with barrier functions. Last inhibit undesirable redistribution of elements at high temperatures. Objective. The establishment of the heat-resisting alloy ХН55ВМТКЮ with a barrier layer (Ti, Zr) N coating titanium aluminizing, the study of phase and chemical compositions, structure, properties. Methods. The barrier layer was applied by physical deposition from the gas phase. Titanium aluminizing was performed in a mixture of powders (wt%): Ti (50); Al (10); Al2O3 (35) NH4Cl (5), in the closed reactionary space in containers with fusible shutter at a temperature of 1050 °C for 4 hours. Resulting in the coating were studied modern methods of materials science: X-ray diffraction, microprobe, metallographic and other physic-methods. Results. The effect of saturation time, cooling rate after HTO, a barrier layer (Ti, Zr) N on the surface of the alloy and structure of the coatings. It is shown that the coating consists of a zone of joints, which includes layers of Ni2AlTi phases, NiAl, Ni0,2Al0,4Ti0,4 (λ-phase), the layers of oxides Ti4Ni2O, Me3Ni3O, Ti(N, O), Al2O3, the inclusion in the zone of the layers, connection-oriented (Ni, Co)7 (Cr, W, Re, Mo)6 (μ-phase), and transition zone. The presence of the barrier layer leads to the formation on the surface of the Ni0,2Al0,4Ti0,4, changes in the structure of the central part of the coating. Instead of small inclusions μ-phase layer of (Ti, Zr) N (method 1), are relatively large inclusions of this phase (method 3). The microhardness of the layer (Ti, Zr) N after HTO was 22.1 GPA. The microhardness of the layers of individual compounds, heterogeneous layers obtained is in the range of 2.4 to 15.3 GPA. Conclusions. Found that when titanium aluminizing of heat resistant alloy ХН55ВМТКЮ diffusion area is formed on the basis of oxides, intermetallic compounds of titanium and aluminum, a barrier layer (Ti, Zr) N with high hardness, high content of aluminum. Obtained coating composition, the structure may be promising in terms of exposure to high temperatures, aggressive environments.

Physical and Chemical Conditions of Complex Saturation Carbon Steel 45 by Silicon and Chrome in Medium of Chlorine

The package of the applied programs with base of the thermodynamic data was used and the theoretical analysis of physical and chemical conditions of complex saturation carbon steel by silicon and chrome in medium of chlorine in the closed reactionary space was carried out at the lowered pressure of a gas phase. The influence of structure of initial components of a sating mix on equilibrium structure gas and condensed of phases of process chromosilicided is revealed. It was theoretically proved that the opportunity of simultaneous application of chrome and silicon on a surface of steel and appearance on steel in medium of chlorine complex diffusion layers is experimentally confirmed based on chrome and silicon. Simultaneous saturation of steel 45 chrome and silicon in chlorine atmosphere for 6 hours at a temperature of 1323 K and a pressure of 10 2 Pa of the gas phase was carried out in this work. The X-ray diffraction studies, it was found that under the assumed conditions of saturation on the steel surface 45 formed diffusion layer thickness of 90–100 microns, which corresponds to the phase of the corresponding chromium carbides Cr 23 C 6 and Cr 7 C 3 , doped silicon (outer coat coatings) and a solid solution of chromium and silicon in α-iron (an inner coatings layer). Using micro X-ray analysis, it was found that the outer zone of the coating of chromium carbide Cr 23 C 6 contains up to 52.87 atomic % chromium, except that it dissolves a small amount of silicon (0.15 % atm.) and iron (up to 15.73 % at.). Located directly underneath the zone based on α- iron which contains 9.87–5.55 % at. chromium, 8.15–3.89 % at. silicon 72.47–84.69 % at. iron.