INVESTIGATION OF THE INTERACTION OF UDP METALS WITH PRODUCTS OF THERMAL DECOMPOSITION OF TETRAZOLE BINDER

В статье приводятся экспериментальные исследования ультрадисперсных металлических порошков алюминия, меди, железа, вольфрама, титана, цинка, никеля, сплавов меди с алюминием, меди с железом и латуни. Описаны термические свойства их смесей с метилполивинилтетразолом, пластифицированным динитратпропиленгликолем; указаны численные величины значимых характеристик.Результаты исследования показали, что существенное количество тепла выделяется при нагреве порошков алюминия, цинка, титана и железа; при нагреве смесей со связующим, наилучшие результаты соответствуют сплаву меди с железом, алюминию и сплаву меди с алюминием. The article presents experimental studies of ultrafine metal powders of aluminum, copper, iron, tungsten, titanium, zinc, nickel, alloys of copper with aluminum, copper with iron and brass. The thermal properties of their mixtures with methyl polyvinyl tetrazole and plasticized propylenglycoldinitrate are described; numerical values of significant characteristics are indicated.The results of the study showed that a significant amount of heat is released when heating aluminum, zinc, titanium and iron powders; when heating mixtures with a binder, the best results correspond to an alloy of copper with iron, aluminum and an alloy of copper with aluminum.

Studying the effect of heat treatment modes on corrosion resistance of welded joints

Welded joints with corrosion-resistant steels and heat-resistant alloys, which require different modes of heat treatment to achieve the level of mechanical properties specified in the design documentation, are used for the manufacture of parts and components of the turbo-pumping unit (TPU) and liquid rocket engine. Heat-resistant alloys are a large group of alloys on iron, nickel and cobalt bases with the addition of chromium and other alloying elements (C, V, Mo, Nb, W, Ti, Al, B, etc.), whose main feature is to maintain high strength at high and cryogenic temperatures. Heat-resistant alloys are used in the manufacture of many parts of gas turbines in rocketry and jet aircraft, stationary gas turbines, the pumping of oil and gas, hydrogenation of fuel in metallurgical furnaces and many other installations. For the doping of nickel chromium γ-solid solution, several elements are used, which differently influence the increase of heat resistance and processability. Along with the main reinforcing elements (Ti, Al), refractory elements (W, Mo, Nb) are introduced into the alloy, which increase the thermal stability of the solid solution. Heat resistant alloys are based on cobalt. Cobalt has a positive effect on the heat-resistant properties of alloys. The introduction of chromium in cobalt increases its heat resistance and hardness. In addition to chromium, alloys containing cobalt include additives of other alloying elements that improve their various properties at high temperatures. A characteristic feature of these alloys is that they have relatively low heat resistance characteristics at moderate temperatures, which, however, change a little with the temperature up to 900 ° C and therefore become quite high compared to the characteristics of other heat-resistant alloys. A significant drawback of these alloys is their high cost due to the costly cobalt. Nickel-based heat-resistant alloys typically have a complex chemical composition. It includes 12–13 components, carefully balanced to obtain the required properties. The content of impurities such as silicon (Si), phosphorus (P), sulfur (S), oxygen (O) and nitrogen (N) is also controlled. The content of elements such as selenium (Se), tellurium (Te), lead (Pb) and bismuth (Bi) should be negligible, which is provided by the selection of charge materials with low content of these elements, because it is not possible to get rid of them during melting. These alloys typically contain 10–12 % chromium (Cr), up to 8% aluminum (Al) and titanium (Ti), 5–10 % cobalt (Co), as well as small amounts of boron (B), zirconium (Zr) and carbon (C). Molybdenum (Mo), tungsten (W), niobium (Nb), tantalum (Ta) and hafnium (Hf) are sometimes added. Heat-resistant alloys are used for the production of many parts of gas turbines in rocketry and jet aircrafts, stationary gas turbines, for pumping oil and gas products, for hydrogenation of fuel in metallurgical furnaces and in many other installations. Nickel-based heat-resistant alloys are also cryogenic, i.e., they are capable of operating and retaining mechanical properties at very low temperatures (–100 °C to –269 °C). Such alloys are chromium-nickel alloys having an austenitic structure. Not only do they have good mechanical properties that do not change over a large temperature range (–200 °C to 900 °C), they can also work in corrosive environments. Nickel-based heat-resistant alloys typically have a complex chemical composition. It includes 12–13 components, carefully balanced to obtain the required properties. Welded and combined workpieces are made of separate components that are interconnected by various welding methods. Welded and combined blanks greatly simplify the creation of complex configuration designs. Improper workpiece design or incorrect welding technology can cause defects (grooves, porosity, internal stresses) that are difficult to correct by machining. Given that finding replacements with multiple materials, working them out in production, and investigating interconnectivity during thermal forces in a product can take considerable time and money, it would be best to replace one alloy. Unifying the material used would allow the structure to work as a whole, which would increase the manufacturability of the products. After examining the different replacement options, inconel 718 was selected for the study. Studies of welded specimens of inconel 718 alloy-stainless steel for resistance to the ICC have shown that it is not appropriate to use welded inconel 718 for the impeller, it is advisable to use material that would ensure uninterrupted operation in a corrosive environment at cryogenic temperatures. Based on the working conditions of the parts, it is most expedient to make it from heat-resistant chromium-nickel alloys, namely, from float inconel 718 which meets the necessary strength characteristics. The recommended soldering mode is heating up to 950 ± 10 oC, holding for 30 minutes from the moment of loading into the oven, cooling to 3000C with the oven, further in the air, since it has less influence on the corrosion resistance of steels in stainless steel joints. Quality control of inconel 718 alloy by GOST methods similar to that used for the control of X67MBHT type alloys showed the results similar to those obtained by the ASTM and AMS control methods.

Iron-Nickel Alloy with Starfish-like Shape and Its Unique Magnetic Properties: Effect of Reaction Volume and Metal Concentration on the Synthesized Alloy

Iron-nickel alloy is an example of bimetallic nanostructures magnetic alloy, which receives intensive and significant attention in recent years due to its desirable superior ferromagnetic and mechanical characteristics. In this work, a unique starfish-like shape of an iron-nickel alloy with unique magnetic properties was presented using a simple, effective, high purity, and low-cost chemical reduction. There is no report on the synthesis of such novel shape without complex precursors and/or surfactants that increase production costs and introduce impurities, so far. The synthesis of five magnetic iron-nickel alloys with varying iron to nickel molar ratios (10–50% Fe) was undertaken by simultaneously reducing Fe(II) and Ni(II) solution using hydrazine hydrate as a reducing agent in strong alkaline media for 15 min at 95–98 °C. The effect of reaction volume and total metal concentration on the properties of the synthesized alloys was studied. Alloy morphology, chemical composition, crystal structure, thermal stability, and magnetic properties of synthesized iron-nickel alloys were characterized by means of SEM, TEM, EDX, XRD, DSC and VSM. ImageJ software was used to calculate the size of the synthesized alloys. A deviation from Vegard’s law was recorded for iron molar ration higher than 30%., in which superstructure phase of FeNi3 was formed and the presence of defects in it, as well as the dimensional effects of nanocrystals. The saturation magnetization (Ms), coercivity (Hc), retentivity (Mr), and squareness are strongly affected by the molar ratio of iron and nickel and reaction volume as well as the total metal concentration.