Heat Resistance Characteristics Research Articles

The effect of heat treatment temperature on the resistance to intergranular corrosion of welded joints of heat-resistant nickel alloys inconel 718 and steel 316l

The effect of heat treatment temperature on the resistance to intergranular corrosion of welded joints of heat-resistant nickel alloys inconel 718 and steel 316l

Study of heat resistance characteristics of metal of centrifugally cast pipes made from 45Kh32N43SB alloy and their welded joints at temperatures up to 1150°C. Part 1: The heat resistance characteristics of pipes at temperatures up to 1100°С

The paper studies heat resistance properties of 45Cr32Ni43SiNb alloy developed at the CRISM “Prometey” for reformer systems of high-temperature ethylene production plants. The macrocrystalline structure is analyzed and quantitative phase data for metal of centrifugally cast tubes is collected. It is shown that the alloy under investigation is characterized by structural stability, long-term durability, and high-temperature creep resistance up to 1000–1100°С.

Numerical investigation and experimental validation of thermo-hydraulic and thermodynamic performances of helical baffle heat exchangers with different baffle configurations

Helical baffle is deemed as a favorable substitute for segmental one. In the present paper, the investigations on fluid flow and heat transfer behaviors are conducted for heat exchangers with eight helical baffle configurations, involving the continuous helical (CH) scheme, quadrant helical (QH) scheme with diverse axial overlapped ratios and novel sextant helical (SH) scheme. The second law of thermodynamics analysis is exploited to further evaluate the irreversibility in helical baffle heat exchangers. Verifications between the experimental data and numerical predictions are performed, and a good agreement is achieved. The parallel and rotational components decomposed from shell-side velocity are detected, and a new conception of the swirl angle is advanced to reveal the stream pattern in helical channel. The leakages passing through conjunction notches between adjacent baffle plates are depicted to check the discrepancy between the spiral and pseudo-spiral flow states. It concludes that the alterations of baffle shapes and assembly arrangements influence the flow field properties significantly. By analyzing the heat transfer, resistance and comprehensive characteristics in shell side, the SH scheme possesses better thermo-hydraulic performance than the CH and QH schemes; moreover, the least entropy generation is received in the SH and QH schemes at low Reynolds number. In addition, larger axial overlapped ratio provides greater heat transfer coefficient and pressure drop but smaller their ratio as well as higher thermodynamic irreversible loss.

Atomic Layer Deposition onto Thermoplastic Polymeric Nanofibrous Aerogel Templates for Tailored Surface Properties.

Poly(vinyl alcohol-co-ethylene) (EVOH) nanofibrous aerogel (NFA) templates were fabricated through vacuum freeze-drying from EVOH nanofibrous suspensions. Aluminum oxide (Al2O3) layers were deposited onto highly porous templates to form organic-inorganic hybrid aerogels by the atomic layer deposition (ALD) technique. Chemical and physical measurements showed that mechanical properties were improved through ALD. In addition, the surface chemistry of ALD modified aerogels showed a fascinating cyclic change based on the number of ALD deposition cycles. A transition from hydrophilicity to hydrophobicity was observed after a few cycles of ALD coating; however, additional deposition cycles changed the wettability characteristics back to hydrophilicity. This hydrophilic-hydrophobic-hydrophilic variation is shown to be governed by a combination of geometrical and chemical surface properties. Furthermore, the deposited Al2O3 could substantially improve aerogels strength and reduce permanent deformation after cyclic compression. The Young's modulus of aerogels increased from 5.54 to 33.27 kPa, and the maximum stress at 80% strain went up from 31.13 to 176.11 kPa, after 100 cycles of trimethyl-aluminum (TMA)/water ALD. Thermogravimetric analysis (TGA) results confirm that ALD can effectively improve the heat resistance characteristics of polymeric aerogel. The onset temperature and the residual mass increased with increasing numbers of ALD cycles. During pyrolysis, the nanofiber cores were decomposed, and the brittle pure Al2O3 self-supporting nanotube aerogels with the continuous hollow nanotubular network were formed. A coating of continuous thickness Al2O3 layer on individual nanofiber was achieved after 100 ALD cycles. In additional to mechanical strength and physical property changes, the ALD modified aerogel also shows a superhydrophobic and oleophilic surface chemistry, which could potentially be used to remove oils/organic solvents from water. The resultant aerogels exhibit excellent absorption capacity (31-73 g/g) for various liquids, and the material could be reused after distillation or squeezing. A successful scale-up of such materials could provide some insights into the design and development of thermoplastic polymeric NFAs with substantial industrial applications.

Ameliorated Mechanical and Dielectric Properties of Heat-Resistant Radome Cyanate Composites.

In order to improve the mechanical and dielectric properties of radome cyanate, a synergistic reinforcement method is employed to develop a resin-based ternary-composite with high heat-resistance and preferable radar-band transmission, which is expected to be applied to fabricate radomes capable of resisting high temperature and strong electric field. According to copolymerization characteristics and self-curing mechanism, epoxy resin (EP) and bismaleimide (BMI) are employed as reinforcements mixed into a cyanate ester (CE) matrix to prepare CE/BMI/EP composites of a heat-resistant radome material by high-temperature viscous-flow blending methods under the catalysis of aluminum acetylpyruvate. The crystallization temperature, transition heat, and reaction rate of cured polymers were tested to analyze heat-resistance characteristics and evaluate material synthesis processes. Scanning electron microscopy was used to characterize the micro-morphology of tensile fracture, which was combined with the tensile strength test and dynamic thermomechanical analysis to investigate the composite modifications on tenacity and rigidity. Weibull statistics were performed to analyze the experimental results of the dielectric breakdown field, and the dielectric-polarization and wave-transmission performances were investigated according to alternative current dielectric spectra. Compared with the pure CE and the CE composites individually reinforced by EP or BMI, the CE/BMI/EP composite acquires the most significant amelioration in both the mechanical and electrical insulation performances as indicated by the breaking elongation and dielectric breakdown strength being simultaneously improved by 40%, which are consistently manifested by the obviously increased transverse lines uniformly distributed on the fracture cross-section. Furthermore, the glass-transition temperature of CE/BMI/EP composite reaches the highest values of nearly 300 °C, with the relative dielectric constant and dielectric loss being mostly reduced to less than 3.2 and 0.01, respectively. The experimental results demonstrate that the CE/BMI/EP composite is a highly-qualified wave-transmission material with preferences in mechanical, thermostability, and electrical insulation performances, suggesting its prospective applications in low-frequency transmittance radomes.

Selection of the Composition of a Multicomponent Alloy of the Nb–Ti–Al–X System with High-Temperature Strength, Heat Resistance, and Technological Efficiency

We establish the physicochemical conditions required for the creation of multicomponent Nb–Ti–Al–X (X – Cr, Zr, Mo, Sr) niobium alloys with improved characteristics of high-temperature strength, heat resistance, and technological efficiency. The conclusions are based on the relationship between the physical properties of alloying elements, enthalpy of mixing, compositions of alloys, and the diagrams of state of the components with specific features of their crystallization caused by alloying.

ELECTRODEPOSITION OF COMPOSITE COATINGS

Galvanic coatings have been attracting attention for many years as an object of research from both theoretical and practical points of view. A relatively new direction in electroplating is the production of composite coatings, which are based on metal matrices and dispersed phases of different nature. Introduction to the electrolyte for joint electrochemical deposition of micro -, nanoparticles of oxides, carbides, nitrides, polymers, etc. allows you to adjust the structure, composition, properties of coatings, providing them with new characteristics. As shown by the analysis of publications on this topic in the VINITI RAS Database, systematic research in this area has been carried out for about twenty years and interest in them has not decreased. The system of queries from the array of published documents selected and summarized all currently known combinations of metal matrix/dispersed phase and information about their properties (corrosion behavior, wear resistance, microhardness, resistance to high-temperature oxidation, heat resistance, structural and adhesive characteristics). The results are presented in the form of tables and are provided with links to the original works. The analysis of the obtained problem-oriented database showed that for the period 2000-2019, no more than 15-20% of possible combinations were described, and an even smaller number of composite coatings were studied in depth and brought to practical use. The presented material makes it possible to analyze promising areas of research in a clear and easy to find source information form. The review is based on more than 400 references to journal articles. The original database on composite electroplating contains 1650 sources (patents, reports, brief reports, deposited manuscripts, etc.) that may be of interest as an extensive reference material.

CANNING FOOD IN SEMI-RIGID POLYMERIC AND COMPOSITE CONTAINERS

For thermal preservation of food, various types of retail polymeric packaging can be used: rigid, semi-rigid, flexible, and other kinds of containers. To make polymeric (plastic) containers usable for thermal sterilisation, and to ensure long storage of food, they should have a barrier layer that will make them heat-resistant, prevent oxygen ingress, and preserve the product’s quality and nutritive value. Every polymer material has its individual heat resistance characteristics. This paper considers such retail containers for food packaging as a composite can made of metal with a plastic lid and a semi-rigid heat-resistant polymer container with a foil cover. When using different container types for heat sterilisation and prevention of physical defects in cans, the following technological characteristics of cans should be taken into account: closure strength, depressurisation pressure, method of closure, diameter of a container’s opening, absence or presence of a stiffness relief on the cover, temperature of packaging, and other factors. The research includes analysis of existing types of retail composite and polymeric containers for canning food using different heat sterilisation methods. The theoretical and experimental research conducted has resulted in obtaining the values of the closure strength of the containers, an important parameter without which proper heat sterilisation of a product would be impossible. Developing scientifically proved parameters and modes of high-temperature sterilisation of meat and fish products in semi-rigid heat-resistant composite metal-plastic containers will allow enterprises to manufacture high-quality and safe canned food with high nutritive value.

Experimental investigation on heat transfer characteristics of supercritical nitrogen in a heated vertical tube

The rapid variations of physical properties near the pseudocritical points and the unique heat transfer and resistance characteristics of supercritical fluids have gained a great deal of attentions in recent years. In this paper, the heat transfer characteristics of supercritical nitrogen in a heated vertical tube are investigated experimentally. The test section is an aluminum alloy tube of 6.6 m in length and 0.02 m in inner diameter with a wall thickness of 0.0085 m. The effects of different operating parameters, including pressure and mass flow rate of nitrogen, inlet temperature and mass flow rate of water, on the heat transfer characteristics are investigated. Meanwhile, the experimental data are compared with the predict values by different existing correlations, and all of them show large differences. Therefore, a new correlation has been developed to accurately predict the heat transfer coefficient based on the experimental data. The new correlation works well with 95% of the experimental data captured with a deviation of 20%. The experimental study and the new correlation may provide reference for the study of the heat transfer of supercritical fluid flow and design and operation of open rack vaporizer (ORV).

Heat Resistance and Electrophysical Characteristics of Polyheteroarylenes and Ferroelectric–Polymer Film Composites Based on Them

Structurally related poly(amido-o-hydroxy amides) derived from 5,5-methylenebis(2-aminophenol) with tetramethylsiloxane and heteroaromatic (benzoxazole and benzotriazole) fragments incorporated in the second amine component or formed by polyheterocyclization of the corresponding prepolymers were prepared. The effect of modifying fragments introduced into the base poly(o-hydroxy amide) on the heat resistance of powders and films and of films of photosensitive compounds based on the synthesized polymers with the naphthoquinone diazide component was analyzed. The electrophysical parameters of the polymer films and film composites with a nanodispersed ferroelectric filler, (PZT: ceramic powder with the composition Pb0.81Sr0.04Na0.075Bi0.075(Zr0.58 Ti0.42)O3, Russian brand PZT-1), prepared on the basis of modified polymer binders, were determined. Introduction of 20 mol % sulfur-containing fragments into the polymer binder ensures a 50–65˚C increase in the heat resistance for all types of films without increasing the level of the dielectric loss for the composite coatings.

Thermal stability and flame-retardant characteristic of irradiated LDPE and composites

Magnesium hydroxide (MH) and alumina trihydrate (ATH) are extensively consumed as fillers in polyolefins to fabricate naturally responsive cables. Halogen-free wires, and especially cross-linked or thermoplastic elastomers, are further prevalent in worldwide use. The limited oxygen index (LOI), cone calorimeter, smoke density and thermogravimetry (TGA) experiments explain the thermal decomposition, flame-retardant and physical characteristics of samples. Results from studies of TGA, smoke emission and LOI testers showed that the thermal strength and flame-retardant characteristics of the samples containing MH compared with corresponding specimens containing ATH have superior thermal stability. The flame-retardant and heat resistance characteristics of samples were improved due to irradiation and the development of cross-linking bonds in the polymer framework. The results of the smoke density experiment show that adding MH to low-density polyethylene (LDPE) results in the lowest smoke density associated with LDPE and LDPE/ATH compounds. This study proved that the inclusion of MH and irradiation of specimens caused a greater thermal strength and also a superior flame-retardant polymeric product compared with the inclusion of ATH to similar irradiated specimens. These successes are useful and appropriate specifically for cable companies to deliver halogen-free flame-retardant cable materials.

Влияние ванадия на микроструктуру и механические свойства слоистых композитов Nb—V / Al, полученных по твердофазной технологии

he microstructure and heat resistance characteristics of layered composites from Nb—V alloys and intermetallic compounds with aluminum are presented. Composites which are made by diffusion welding under pressure have structures from alternate foils of niobium doped with vanadium with 5, 10 and 15% (at.) and hardening layers of aluminum. It has been found out that the alternation of viscous-plastic layers of Nb—V alloy and hardening layers of aluminum ensures high strength of the composites at 20—1300 °С temperature, that increases when vanadium content in Nb—V alloy increases.

Identifying the properties of epoxy composites filled with the solid phase of wastes from metal enterprises

The article addresses the issue related to the disposal of dust from steel industry as a reinforcing filler for epoxy composites. The polymer composition of welding that has been developed and studied includes epoxy dian oligomer, amine hardener and the filler – finely dispersed waste of metals. Polyethylene polyamine was used as a hardener in order to improve heat resistance and strength characteristics. Manganese triacetate was used in order to decrease the temperature and reduce the time of curing. The possibility was established to dispose of finely dispersed metal-containing waste from metallurgical production to be used a filler for epoxy composites of cold curing. It was revealed that the optimal content of dusts from foundries in the composite is at the level of 45–60 %. At this content, there is the highest impact resistance at the level of 40–50 MPa and a softening temperature in the range of 170–190 °С. It was established that at an increase in the amount of a filler from 40 % to 70 %, the cross-linking degree increases by 88 % to 98 %, respectively. However, at the content of the filler less than 45 % or exceeding 60 %, the impact resistance of the resulting composites decreases. At the content of a filler in the composite less than 45 %, the cause of low values of impact resistance and softening temperature could be the low cross-linking degree, less than 90 %. A decrease in these properties of composites at the content of the filler exceeding 60 % could be associated with the formation of a heterogeneous structure of filler. In the compositions with the highest performance characteristics, there is an optimized content of the filler and catalyst. Using a hardener and a curing catalyst in quantities of 3–3.5 and 1.5–2 %, respectively, makes it possible to shorten curing time by up to 2 hours. In general, the resulting epoxy composites are superior in their performance to known cold-curing analogs. The dependences of impact resistance, softening temperature, and cross-linking degree on the content of waste in the composite were derived, which make it possible to calculate the optimal formulation for composites depending on the required properties

КЛАССИФИКАЦИЯ ТЕХНОЛОГИЙ УПРОЧНЕНИЯ, НАНЕСЕНИЯ ПОКРЫТИЙ И ВОССТАНОВЛЕНИЯ ДЕТАЛЕЙ ТОПЛИВНОЙ АППАРАТУРЫ ДИЗЕЛЬНЫХ ДВИГАТЕЛЕЙ

During operation, any technical product with friction units, as parts wear out, loses its working capacity and as a result cannot perform the specified functions with the parameters, established by the requirements of technical documentation. Today, the technological capabilities of manufacturing various machines and mechanisms have been exhausted throughout the world without noticeable wear on the mating surfaces of friction units. Depreciation is practically impossible to exclude. Therefore, a search for new ways to extend the life of technical devices by exposing them to friction surfaces is an urgent task. These requirements apply to the fuel equipment of automotive and combine diesel engines. In this paper, we analyze the known covering technologies for hardening and restoration of fuel equipment parts. The methodology of choosing the optimal covering process with the aim of hardening and restoration of parts of fuel equipment is formulated. In accordance with this concept of choosing a technology to increase the durability of fuel equipment parts, plasma finish hardening with the application of multilayer wear-resistant coatings is a promising technology. The paper presents the results of a study of the physicomechanical properties of diamond-like coverings of the DLCPateks type (a-C:H/a-SiOCN) obtained on friction surfaces by transporting an atomic and molecular stream of particles of liquid chemical compounds by a plasma jet of an atmospheric pressure plasma arc torch. The layer formed on the working surfaces is a non-metallic amorphous multilayer covering with a low coefficient of friction, increased microhardness, chemical inertness, hydrophilicity, high heat resistance and dielectric characteristics. In order to minimize possible defectiveness of the base material at the final stage of manufacturing parts of fuel equipment, it is proposed to apply thin-film coatings on them.

Coupling Effect of Heat Transfer and Flow Resistance in the Rifled Tube Water Wall of a Ultra-Supercritical CFB Boiler

The coupling factor is used in this study to characterise the combined effect of the heat transfer and resistance characteristics of a rifled tube. Boundary layer theory is utilised to investigate the relationship between the comprehensive coefficient and Reynolds number in two regions, namely, higher and lower than pseudo-critical enthalpy. Results indicate that mass flux exerts a decisive negative influence on the coupling effect, and the impacts of pressure and heat flux are weak. The overall effect decreases rapidly as the mass flux increases, but it increases in the area behind the quasi-critical enthalpy. The coupling effect is also affected by specific heat ratio, thermal acceleration and buoyancy. The correlations of heat transfer and friction resistance are deduced with high precision according to experimental data.

Performance of shell-and-tube heat exchangers with different baffles applied to water chillers based on fluid–structure interaction

As one of the substitutes for R134a in chillers, the refrigeration performance of R450A is poor. Heat exchanger structural improvement is proposed to improve its refrigeration performance in chillers. In this article, the heat transfer characteristics, resistance characteristics, and stress characteristics of shell-and-tube heat exchangers (STHXs) with different baffles (segmental baffles [SB], plane helical baffles [PB], fold helical baffles [FB]) are numerically investigated based on the fluid–solid coupling. The results show that the shell-side flow velocity and temperature difference of STHXsSB are the highest, and those of STHXsPB are the lowest. The heat transfer coefficient and pressure drop of STHXs increase gradually with the increase of the shell-side volume flow, but h/ΔP decreases gradually. Compared with h/ΔP of STHXsSB, that of STHXsPB increases by 62.2–65.7%, and that of STHXsFB increases by 73.9–76.1%. The stresses around the holes of the baffles are higher than other parts of the baffles. Besides, the effect of temperature on the baffle stress distribution is much greater than that of pressure. Although the maximum stress of STHXsFB is the highest, it is in the allowable stress range of the material. Hence, STHXsFB is suitable for water chillers due to its excellent comprehensive performance.

Research status and development of explosive welded metal materials

Explosive welding composites have been widely used in aerospace, petroleum, chemical, military and other fields, because of their characteristics of corrosion resistance, heat resistance and high strength. The theoretical research of metal explosive welded materials was introduced systematically, and the significance and trends of interface research were analyzed in this paper. Finally, the development trend of explosive welding of metal materials is prospected. It is pointed out that the prediction of damage behavior of explosive welding composites in service environment has certain scientific significance and engineering application value.

Study on Characteristics of Heat Transfer and Flow Resistance in Random Porous Foam Metal

Porous foam metal has great application prospects in the field of compact heat exchangers. The characteristics of heat transfer and resistance for foam metal with random structure and different porosities (30%, 50%, 70% and 90%) were studied by finite element method in this study. The generated foam structures can be considered as homogeneous model and has better heat exchange capacity at higher inlet flow rate, and the boundary layer can develop well along the flow direction. The open–cell foammetal structure has a uniform heat transfer perpendicular to the flow direction. The bottom plate temperature of the low–porosity structure is more uniform at low flow rates. The intermediate porosities (50% and 70%) at high flow rates has a higher uniformity. As the porosity decreases, the internal pressure increases significantly and the pressure loss also becomes significantly larger. The corresponding optimal porosity is 57%, 66% and 76% at inlet flow rates of 0.001 m/s, 0.01 m/s and 0.1 m/s, respectively.

Ultralight large grain porous material - expanded obsidian

In the production of crushed stone, lithoidal pumice and perlite sand, it is advisable to separate and segregate the obsidian. Wherein, the separated obsidian is converted into production waste. By the expansion of obsidian it is possible to obtain an ultralight large grain porous material and thereby solve environmental issues - to dispose of waste products. The expansion of volcanic glass (obsidian) occurs due to gases, primary (magmatic) and secondary (hydraulic) water, which is located in the pores. During the expansion, under heat treatment, the gases expand about 4 ... 5 times in the pores, which contributes the expansion. Expanded obsidian can be used as a filler for lightweight concrete. Obsidian is expanded at temperatures of 1050-115°C. The lowest average density of 200 - 350 kg / m3 (in a piece) is obtained by heat treatment of obsidian with a particle size of 5 to 20 mm for a duration of 3-10 minutes. Depending on the requirements for lightweight aggregates, by adjusting the firing temperature and duration, it is possible to obtain expanded obsidian with the necessary physical and mechanical properties. It is revealed that more durable concretes are obtained with cement consumption of 350 ... 380 kg. Depending on the average density of lightweight concrete 400 .. 1350 kg/m3, the compressive strength is 0.2 ... 16,9 MPa. Light monolithic products with improved characteristics of heat resistance and thermistance, having an average density of 180-200 kg/m3, compressive strength of 1.2–1.5 MPa, frost resistance of 25 cycles, after which the strength changes to 1.0–1.3 MPa, heat resistance to 800–850°C, and thermistance to 600–650°C. By the thermal conductivity coefficient determination it was possible to reveal that in the temperature range of 20-60°C, the thermal conductivity coefficient changes by 0.002 W/mK, i.e. from 0.044 to 0.046 w/mK. Thus, the obtained monolithic blocks can be very successfully used as heat-insulating materials, which will retain their properties throughout the operation of the facilities. The requirements for mechanical strength and decorative properties for sound-absorbing materials compared to thermal insulating materials are higher, since they are used for internal linings. Thus, the obtained monolithic blocks can be very successfully used as heat-insulating materials, which will retain their properties throughout the operation of the facilities.

Finished plasma strengthening and restoration of fuel equipment details

The results of the investigation of the physical and mechanical properties of diamond-like coatings of the DLCPateks type (a-C: H / a-SiOCN) obtained on friction surfaces by transporting the atomic and molecular flux of vapor particles of liquid chemical compounds by a plasma jet of an arc plasma torch of atmospheric pressure are presented. The layer formed on the working surfaces is a non-metallic amorphous multilayer coating with a low coefficient of friction, increased microhardness, chemical inertness, hydrophilicity, high heat resistance and dielectric characteristics. To minimize the possible defectiveness of the main material, it is proposed to apply thin-film coatings to them at the final stage of manufacturing fuel equipment parts.