DIFFUSION TITANIUM ALUMINIZING OF HEAT RESISTANT ALLOY ХН55ВМТКЮ IN THE CLOSED REACTIONARY SPACE
DOI:
https://doi.org/10.20535/2305-9001.2016.76.67137Keywords:
superalloy, titanium, aluminum, barrier layer, oxides, intermetallics, microhardness.Abstract
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.References
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