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

2021 ◽  
pp. 23
Author(s):  
Nataliya Kalinina ◽  
Vasiliy Kalinin ◽  
Ivannа Serzhenko
Keyword(s):  
Mechanical Properties ◽  
Heat Resistance ◽  
Inconel 718 ◽  
Gas Turbines ◽  
Nickel Alloys ◽  
Oil And Gas ◽  
Inconel 718 Alloy ◽  
Heat Resistant ◽  
Complex Chemical Composition ◽  
Metallurgical Furnaces

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.

scholarly journals Predicting the properties of nickel-based superalloys directional crystallization

2021 ◽  
Vol 99 (3) ◽  
pp. 15-22
Author(s):  
O.A. Glotka ◽  
◽  
V.Yu. Olshanetskii ◽  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Heat Resistance ◽  
Regression Models ◽  
Nickel Alloys ◽  
Alloying Elements ◽  
Directional Crystallization ◽  
Heat Resistant ◽  
Basic Characteristics ◽  
Main Components

The aim of this work is to obtain predictive regression models, with which it is possible to adequately calculate the mechanical properties of heat-resistant nickel alloys, without prior experiments. Industrial alloys of directional crystallization of domestic and foreign production were selected for research. The values were processed by the method of least squares to obtain correlations with the receipt of mathematical equations of regression models that optimally describe these dependencies. As a result of processing of experimental data, the ratio of alloying elements which can be used for an estimation of mechanical properties taking into account complex influence of the main components of an alloy is offered for the first time. Since the dimensional mismatch of the lattice parameters is associated with the degree of concentration of solid-soluble hardening of γ- and γ'-phases, the efficiency of dispersion hardening of the alloy, creep rate and other properties, the obtained ratio allows to link these properties with multicomponent systems. Regression models are presented, with the help of which it is possible to calculate dimensional mismatch, strength, heat resistance, number of  phases and density of alloys with high accuracy. The regularities of the composition influence on the properties of heat-resistant nickel alloys of directional crystallization are established. It is shown that for multicomponent nickel systems it is possible to predict with high probability misfit, which significantly affects the strength characteristics of alloys of this class. The decrease in the value of misfit is accompanied by an increase in the solubility of the elements in the -solid solution at a value of the ratio of alloying elements of 1.5 - 1.6. However, an increase in the ratio of alloying elements greater than 2 is accompanied by an increase in misfit, because the -solid solution has reached a maximum of dissolution. The perspective and effective direction in the decision of a problem of forecasting of the basic characteristics influencing a complex of service properties of alloys both at development of new heat-resistant nickel alloys, and at perfection of structures of known industrial marks of this class is shown. Keywords: nickel-based superalloys, dimensional mismatch (γ / γ'- mismatch), strength, heat resistance.

Evaluation of the Performance of Inconel 718 Fasteners Subjected to Cathodic Protection Systems in Offshore and Subsea Applications

2011 ◽  
Author(s):  
Fabio Pires ◽  
Richard Clements ◽  
Fabio Santos ◽  
Judimar Clevelario ◽  
Terry Sheldrake
Keyword(s):  
Mechanical Properties ◽  
Cathodic Protection ◽  
Inconel 718 ◽  
Nickel Alloys ◽  
High Strength ◽  
Maximum Hardness ◽  
Inconel 718 Alloy ◽  
Protection Systems ◽  
Impressed Current ◽  
Current Systems

Fasteners manufactured with Inconel 718 alloy are being widely used in offshore and subsea applications due to the material’s high strength, when compared to other nickel alloys, and its inherent corrosion resistance. However, concerns have been raised over its utilization in applications where cathodic protection or impressed current systems are in place. These concerns relate to the susceptibility to hydrogen embrittlement that Inconel 718 alloy may present depending on its processing, microstructure, hardness and actuating stresses. Over the last few years, much has been discussed on the suitability of the alloy for subsea applications. The development of special thermal cycles for the ageing of the alloy has been necessary to provide a consistent material with a maximum hardness of 35 HRc, and a microstructure free of detrimental phases without jeopardizing the overall mechanical properties of the alloy. Wellstream has developed a test programme focused on the assessment of Inconel 718 behavior when subjected to cathodic protection systems. Through this programme, it was possible to demonstrate the suitability of Inconel 718 alloy in subsea applications when the resulting microstructure and hardness are properly controlled, and bolt loading is within normal working limits.

Research on Mechanical Properties of Thin Sheets Blanks Made of Creep-Resisting Nickel Superalloys

2013 ◽  
Vol 212 ◽  
pp. 259-262
Author(s):  
Monika Hyrcza-Michalska
Keyword(s):  
Mechanical Properties ◽  
Inconel 718 ◽  
Nickel Alloys ◽  
Thin Sheet ◽  
High Strength ◽  
Inconel 625 ◽  
Thin Sheets ◽  
Inconel 718 Alloy ◽  
Mechanical Working ◽  
Inconel Alloys

Mechanical working manufacturing methods of nickel alloys used conventionally strips and blanks need to solve many problems concerning high strength material forming which is characteristic limited plasticity. The production pressed elements of vehicle constructions and aircraft engine elements requires the high quality drawpieces since these are essential for safety. They are also the main structural components. Conventional methods of mechanical working such as pressing can be used in quantity production of the above mentioned elements and their production can also be cost-effective. Forming nickel alloys generates a lot of technological wastes resulting from back-springing effects determining the most appropriate pressure in the process of pressing. Failure holes in the process of bulging as well as cracking of drawpieces in the process of deep drawing. The heterogeneous mechanical properties distribution on thin sheet blanks made of Inconel alloy, which is different than material quality certificate shows, produces also a lot of manufacturing problems. These problems are usually solved by production engineers in the following way: dividing the production of ready drawpieces into a bigger number of simple blank profiling operations, shallow pressing, using a rubber punch for pressing or hydroforming. Complex drawpieces shapes are quite often made of several parts which are next welded. In the case of presented tube a tubular diffuser made of Inconel 718 alloy blank and cone made of Inconel 625. However the process of forming high strength materials like nickel alloys requires the application bigger forming forces than in the same kind of conventional formable steel processes. Tools get jammed quite often in the process and high force presses of 10 MN or more need to be used so is very expensive. The aspect of cold mechanical forming discussed materials has been a particular interest. The researches based on precise evaluation mechanical properties and technological plasticity of the selected materials in basic mechanical and technological tests as well as in FEM numerical simulation (finite elements method). The material models applied to simulation contain the pointed out experimentally the mechanical characteristics of Inconel alloys. The thin sheets blanks made of 0,9 mm thick Inconel 718 alloy and 0,45 mm thick Inconel 625 alloy blanks have been examined. The possibilities of using numerical simulations for solving the problems of selecting or modifying the pressing technology and hydroforming that type materials as well as forecasting the results of forming processes have been also presented. The evaluation of drawability of thin sheets blanks made of Inconel 718 and 625 alloys has also been discussed in the paper.

scholarly journals Розробка технології дисперсного модифікування жароміцних нікелевих сплавів для лопаток газотурбінних двигунів

2021 ◽  
pp. 49-53
Author(s):  
Наталія Євграфівна Калініна ◽  
Олександр Васильович Калінін ◽  
Тетяна Валеріївна Носова ◽  
Стелла Ігорівна Мамчур ◽  
Наталія Іванівна Цокур
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Heat Resistance ◽  
Nickel Alloys ◽  
Effective Means ◽  
Primary Crystallization ◽  
High Temperature Corrosion ◽  
Rotor Blades ◽  
Initial State ◽  
Heat Resistant

The paper proposes means of improving the properties of nickel alloys for aircraft gas turbine engines by improving the existing alloys. The efficiency of an aircraft engine depends on the quality of the turbine rotor blades, which are made of heat-resistant alloys. According to the studies, the obtained results of pilot tests of a complex of mechanical properties, high-temperature corrosion of a multicomponent high-temperature nickel alloy ХН59МВТКЮЛ (Ni-Cr-W-Co-Al-Ti-Mo systems). The paper proposes the use of modifiers. An effective means of dispersing the structural components of alloys at the macro and micro levels is the modification of multicomponent alloys with dispersed and nano dispersed compositions. Based on titanium nitride powder, a technological regime for modifying nickel melt with dispersed compositions of plasma chemical synthesis has been developed. The modifier was used in tablet form. Investigated different dosages of the modifier: 0.1…0.03 % by weight. The proposed method allows, with minimal losses at the melting stage, to introduce the required amount of modifier. The temperature and time parameters of the modification are 16500С, the modifier action time is 5…7 minutes. Investigations of the complex mechanical properties and the peculiarities of the formation of the structure of the modified alloy have been carried out. According to the research results, significant refinement of the alloy grain was obtained in comparison with the initial state. The modification led to an increase in mechanical properties: strength by 10 %, impact strength by 35...40 %. Comparison of the nano-modified alloy with the obtained one made it possible to increase the corrosion resistance of the ХН59МВТКЮЛ alloy in an oxidizing environment. At a temperature of 1000 0С, the corrosion depth decreased by 15 %. An increase in resistance to high-temperature corrosion is associated with a more uniform distribution of excess phases in the structure of the modified alloy. The mechanism of action of refractory particles of a modifier in a nickel melt, which are the nuclei of primary crystallization, has been established. The results of the work are of practical value in the manufacture of rotor blades from high-quality heat-resistant nickel alloys with increased parameters of heat resistance and heat resistance.

Precipitation of γ″ in Inconel 718 alloy from microstructure to mechanical properties.

Materialia ◽  
2021 ◽  
pp. 101187
Author(s):  
Alexandre Balan ◽  
Michel Perez ◽  
Thibaut Chaise ◽  
Sophie Cazottes ◽  
Didier Bardel ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Inconel 718 ◽  
Inconel 718 Alloy

scholarly journals Anisotropy Study of Inconel 718 alloy at Sub-Zero temperatures

2020 ◽  
Vol 184 ◽  
pp. 01004
Author(s):  
L Jayahari ◽  
K Nagachary ◽  
Chandra Ch Sharath ◽  
SM Hussaini
Keyword(s):  
Mechanical Properties ◽  
Strain Hardening ◽  
Inconel 718 ◽  
Anisotropy Parameter ◽  
Tensile Tests ◽  
Strain Hardening Exponent ◽  
Inconel 718 Alloy ◽  
Normal Anisotropy ◽  
Axial Tensile ◽  
Forming Characteristics

There is an increase in demand for new alloys in aerospace, power generation and nuclear industries. Nickel Based super alloys are known for having distinctive properties which are best suitable for these industries. In this study Nickel based super alloy Inconel 718, is used. Over the many years of intense research and development, these alloys have seen considerable evolution in their properties and efficiency. Behaviour of materials and its forming characteristics can be precisely analysed by determining anisotropic behaviour and mechanical properties. In the present study, tried to analyse the mechanical properties of Inconel 718 like yield strength (Ys), ultimate tensile strength (UTS), strain hardening exponent (n) and strain hardening coefficient (k). Uni-axial tensile tests were conducted on specimens with various parameters such as orientations, temperature and Strain rate. Anisotropy of Inconel 718 alloy was measured based on measurable parameters. The normal anisotropy parameter (f) and planer anisotropy (Δr) were measured and observed that the anisotropy parametres are incresed with the decrease in temperature.

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