Examination of the plastic properties of zircaloy-4 at elevated temperatures in air atmosphere

1976 ◽  
Vol 62 (1) ◽  
pp. 26-36 ◽  
Author(s):  
M. Boček ◽  
G. Faisst ◽  
C. Petersen
Keyword(s):  
Elevated Temperatures ◽  
Plastic Properties ◽  
Air Atmosphere

Process Design for Superalloys Sheet Rotary Forming

2020 ◽  
Vol 985 ◽  
pp. 91-96
Author(s):  
Krzysztof Zaba ◽  
Sandra Puchlerska ◽  
Tomasz Pieja ◽  
Jaroslaw Pyzik
Keyword(s):  
Process Design ◽  
Elevated Temperatures ◽  
Nickel Superalloy ◽  
Inconel 625 ◽  
Quality Factors ◽  
Forming Process ◽  
Plastic Properties ◽  
Temperature Oxidation ◽  
Wide Range ◽  
The Impact

Inconel 625 is a nickel superalloy, characterized by high fatigue strength. The alloy is resistant to a wide range of corrosive environments, including high-temperature oxidation. For this reason, it is an attractive material for the chemical, shipbuilding and aviation industries. Inconel 625 alloy is designed for plastic working. However, the significant difficulty is the appropriate process design, due to the high deformation resistance. In order to improve the plastic properties of the alloy, processing at elevated temperatures is practiced. In this work, attempts were made to implement rotary forming process of Inconel 625 superalloy. For this purpose, an experiment was designed, investigating the impact of three variables on the process – feed rate, spinning rate and heating. For the tests were used Inconel 625 metal plates in the shape of discs. Axial-symmetrical products were formed, using a spinning machine. The geometry of the products according to selected quality factors was investigated. Optimal process parameters were chosen using multivariate statistical optimization. These parameters will be used to set up processes to obtain product that meets quality requirements.

Comparisons of cyclic fatigue hysteresis between C/SiC and SiC/SiC ceramic–matrix composites with different fiber preforms at room and elevated temperatures

2020 ◽  
Vol 54 (20) ◽  
pp. 2723-2737
Author(s):  
Li Longbiao
Keyword(s):  
Room Temperature ◽  
Elevated Temperatures ◽  
Ceramic Matrix Composites ◽  
Cyclic Fatigue ◽  
Inert Atmosphere ◽  
Dissipated Energy ◽  
Matrix Composites ◽  
Cycle Number ◽  
Air Atmosphere ◽  
Sic Ceramic

In this paper, the cyclic fatigue hysteresis of carbon fiber reinforced silicon carbide (C/SiC) and SiC/SiC ceramic–matrix composites with different fiber preforms at room and elevated temperatures is investigated. The evolution of fatigue hysteresis dissipated energy versus applied cycle number for unidirectional C/SiC ( σmax = 240 MPa at room temperature and σmax = 250 MPa at 800℃ in air atmosphere), cross-ply C/SiC ( σmax = 105 MPa at room temperature and 800℃ in air atmosphere), 2D C/SiC ( σmax = 387 and 425 MPa at room temperature), 2.5D C/SiC ( σmax = 180 MPa at room temperature, σmax = 140 MPa at 800℃ in air atmosphere, and σmax = 230 MPa at 600℃ in inert atmosphere), 2D SiC/SiC ( σmax = 130 MPa at 600℃, 800℃, and 1000℃ in inert atmosphere, σmax = 80 MPa at 1000℃ in air atmosphere, σmax = 100 MPa at 1000℃ in steam atmosphere, σmax = 140 MPa at 1200℃ in air and in steam atmospheres, σmax = 90, 120 MPa at 1300℃ in air atmosphere), and 3D SiC/SiC ( σmax = 100 MPa at 1300℃ in air atmosphere) is analyzed. The change rate of the fatigue hysteresis dissipated energy between C/SiC and SiC/SiC composites is compared. The fatigue hysteresis dissipated energy decreases with applied cycle number for unidirectional, and cross-ply C/SiC composite at 800℃ in air, and 2.5D C/SiC composite at 600℃ in inert; and the fatigue hysteresis dissipated energy increases with applied cycle number for 2.5D C/SiC composite at 800℃ in air, 2D SiC/SiC composite at 600℃, and 800℃ in inert.

Degradation of oxide varistor ceramics in air atmosphere containing NO2 at elevated temperatures

2004 ◽  
Vol 24 (6) ◽  
pp. 1213-1216 ◽  
Author(s):  
Alexander Glot ◽  
Elisabetta Di Bartolomeo ◽  
Aleksei Gaponov ◽  
Riccardo Polini ◽  
Enrico Traversa
Keyword(s):  
Elevated Temperatures ◽  
Air Atmosphere

Temperature Dependence of High-Cycle Fatigue Behavior of a Ni-Base Single Crystal Superalloy

2007 ◽  
Vol 546-549 ◽  
pp. 1219-1224 ◽  
Author(s):  
Y. Liu ◽  
Jin Jiang Yu ◽  
Yan Xu ◽  
Xiao Feng Sun ◽  
Heng Rong Guan ◽  
...  
Keyword(s):  
Single Crystal ◽  
High Cycle Fatigue ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Testing Temperature ◽  
Cycle Fatigue ◽  
Air Atmosphere ◽  
Ultimate Failure ◽  
Increasing Temperature

Smooth specimens of single crystal (SC) superalloy SRR99 with [001] orientation were subjected to high-cycle fatigue (HCF) loading at temperatures of 700°C, 760°C, 850°C and 900°C in air atmosphere. The results demonstrated that conditional fatigue strength reached the maximum at 760°C and decreases with increasing temperature. Analysis on fracture surface showed a trend for cleavage rupture at 850°C and 900°C and ductile rupture at 700°C and 760°C. Fatigue cracks initiated at the surface or subsurface were primarily responsible for the ultimate failure. The influence of testing temperature on fatigue lifetime was studied by examining evolution of the microstructure through SEM observation. With the process of cyclic loading at elevated temperatures, the primary cuboidal γ′ precipitates tended to agglomerate and spheroidized, meanwhile a larger number of secondary γ′ particles were formed in the γ matrix in specimens fatigue tested at 700°C, which would have a significant effect on the high temperature properties.

scholarly journals The Process of Regenerative Heat Treatment of the Valve Chamber of the Steam Turbine

2019 ◽  
Vol 26 (3) ◽  
pp. 243-248
Author(s):  
Agata Wieczorska
Keyword(s):  
Steam Turbine ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Cast Steel ◽  
Degradation Process ◽  
Steam Turbines ◽  
Regenerative Heat ◽  
Plastic Properties ◽  
Term Operation ◽  
Dynamic Damage

Abstract Steel castings are often used in the construction of valve chambers of steam turbines. Stringent requirements are set due to the continuous operation of the material at elevated temperatures, in the order of 300°C to 600°C. The material of the valve chamber must be resistant to fatigue-creep changes as well as corrosion. This material must be also resistant to dynamic damage which occures when the turbine is starting and stopping. Dynamic damage is induced by a short-lasting but intense accumulation of localized stresses. The castings of the valve chambers of the steam turbine are usually made from the “three-component” type CrMoV-cast steel. Mentioned castings of the valve chamber are continuously subjected to high temperatures, either constant and periodically variable stresses. Due to this, the degradation process of material of the castings is taking place. It is caused by physicochemical processes such as: creep, relaxation, thermal fatigue, corrosion, erosion and changes in material properties, e.g. displacement of the critical point of brittleness. Finally, first cracks and deformations can be observed in the material during the operation. The art presents the process of revitalization technology of the steam turbine valve chamber which was subjected to long-term operation at high temperatures. The revitalization process is aimed at improving the plastic properties of the material and, as the result, extending its service life. The research presented in the article show that impact strength of the chamber material after revitalization is very high. Also the strength properties of the valve chamber, after revitalization, are high and in line with the requirements. The study show that the revitalization of the valve chamber was carried out correctly and restored the material to plastic deformation.

scholarly journals Reaction mechanism and kinetics of sulfide copper concentrate oxidation at elevated temperatures

10.30544/320 ◽  
2017 ◽  
Vol 23 (3) ◽  
pp. 267-280 ◽  
Author(s):  
Aleksandra Mitovski ◽  
Nada Štrbac ◽  
Miroslav Sokić ◽  
Milan Kragović ◽  
Vesna Grekulović
Keyword(s):  
Reaction Mechanism ◽  
Elevated Temperatures ◽  
Oxidation Process ◽  
Reaction Rates ◽  
Oxidation Products ◽  
Arsenic Content ◽  
Iron Sulfides ◽  
Initial Sample ◽  
Copper Concentrate ◽  
Air Atmosphere

Sulfide copper concentrate from domestic ore deposit (Bor, Serbia) was subjected to oxidation in the air atmosphere due to a better understanding of reaction mechanism and oxidation of various sulfides present in the copper concentrate at elevated temperatures. Results of the initial sample characterization showed that concentrate is chalcopyrite–enargite-tennantite type, with an increased arsenic content. Characterization of the oxidation products showed the presence of sulfates, oxysulfates, and oxides. Based on predominance area diagrams for Me-S-O systems (Me = Cu, Fe, As) combined with thermal analysis results, the reaction mechanism of the oxidation process was proposed. The reactions which occur in the temperature range 25 – 1000 °C indicate that sulfides are unstable in the oxidative conditions. Sulfides from the initial sample decomposed into binary copper and iron sulfides and volatile arsenic oxides at lower temperatures. Further heating led to oxidation of sulfides into iron oxides and copper sulfates and oxysulfates. At higher temperatures sulfates and oxysulfates decomposed into oxides. Kinetic analysis of the oxidation process was done using Ozawa’s method in the non-isothermal conditions. The values for activation energies showed that the reactions are chemically controlled and the temperature is the most influential parameter on the reaction rates.

scholarly journals Surface Degradation of Ductile Metal in Elevated Temperature Gas-Particle Streams

1985 ◽  
Author(s):  
Alan Levy ◽  
Yong-Fa Man
Keyword(s):  
Erosion Rate ◽  
Loss Rate ◽  
Elevated Temperatures ◽  
Negative Slope ◽  
Material Loss ◽  
Loss Mechanism ◽  
High Loss ◽  
Air Atmosphere ◽  
Continuous Scale ◽  
Erosion Corrosion

The mechanisms and rates of erosion and combined erosion-corrosion of 9CrlMo steel and 310SS at elevated temperatures were investigated to better understand the behavior of piping steels in fluidized bed combustor environments. Tests were performed in a partially inert gas atmosphere to study erosion behavior and in an air atmosphere to study combined erosion-corrosion behavior. It was determined that the erosion rate remained constant or decreased with temperature in nitrogen until a temperature was reached at which the tensile strength v.s. temperature curve of the alloy markedly changed its negative slope. Above this temperature the erosion rate increased rapidly with temperature. In an erosion-corrosion environment corrosion was the dominant mechanism at all test conditions. At higher temperatures and velocities the material loss mechanism changed from low loss rate chipping of the scale to high loss rate periodic spalling. The continuous scale formed on 9CrlMo steel in air appeared to protect the metal surface, decreasing its loss rate in α=30° tests compared to that of 310SS tested at the same conditions in nitrogen where a continuous scale did not form.

Electrophoretic Deposition of Nanocrystalline BaTiO3 in Ethanol Medium

2006 ◽  
Vol 314 ◽  
pp. 133-140 ◽  
Author(s):  
Aydin Dogan ◽  
Göktuğ Günkaya ◽  
E. Suvaci ◽  
Markus Niederberger
Keyword(s):  
Electrophoretic Deposition ◽  
Elevated Temperatures ◽  
Deposition Process ◽  
Xrd Analysis ◽  
Titanium Isopropoxide ◽  
One Pot ◽  
Flat Surfaces ◽  
Air Atmosphere ◽  
Coating Method ◽  
Optimal Process Control

Electrophoretic deposition technique is a versatile coating method. With this method not only flat surfaces but also curved or rough surfaces can be coated in various thicknesses. In this study, BaTiO3 nanocrystals were synthesized with a novel nonaqueous method. In a simple one pot reaction process, the metallic barium is directly dissolved in benzyl alcohol at slightly elevated temperatures. After the addition of titanium isopropoxide and subsequent solvothermal treatment nearly spherical BaTiO3 nanocrystals typically 5 nm in diameter were obtained. The stability of the suspension in ethanol and nanocrystalline particle size distribution was measured by Malvern Nano-ZS. The BaTiO3 suspensions were directly used in an electrophoretic deposition process without any additional operation. Pt plated alumina was used as substrate. Various voltages were applied by altering the cathode to anode distance as well as deposition time for optimal process control. Because of the ethanol adsorbed on the surface of the nanoparticles, application of high voltages was possible without causing hydrolysis. The deposited surface coatings were dried in air atmosphere and sintered at different temperatures. SEM, EDX and XRD analysis were employed for the investigation of the coating.

scholarly journals Investigation of Bi2S3 oxidation process at elevated temperatures in the air atmosphere

Tehnika ◽  
2020 ◽  
Vol 75 (6) ◽  
pp. 587-593
Author(s):  
Nada Štrbac ◽  
Miroslav Sokić ◽  
Aleksandra Mitovski ◽  
Dejan Gurešić ◽  
Kristina Božinović ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Elevated Temperatures ◽  
Oxidation Process ◽  
Oxidation Products ◽  
X Ray Diffraction ◽  
Gibbs Free Energy Change ◽  
Stability Diagrams ◽  
Air Atmosphere ◽  
Different Temperatures ◽  
Sulfide Concentrates

Bismuth (III) sulfide has been widely researched in recent years due to its application, but little emphasis has been placed on research regarding its behavior at elevated temperatures. This is of great importance, considering that bismuth, in the form of Bi2S3, is found in copper sulfide concentrates and is considered one of the most harmful components, along with lead, arsenic and antimony. The removal of these substances is one of the basic tasks in the processes of pyrometallurgical extraction of copper, in order to obtain a high purity metal. In order to better understand the behavior of bismuth (III) sulfide during oxidation at elevated temperatures, this paper characterized the synthesized sample of Bi2S3 at room temperature and the oxidation products at 500 °C by X-Ray diffraction (XRD), as well as thermodynamic, thermal and kinetic analysis of the oxidation process of Bi2S3 at elevated temperatures. In order to understand the behavior of Bi2S3 during oxidation and the distribution of oxidation products, phase stability diagrams in the Bi-S-O system were constructed at different temperatures and the values of the Gibbs free energy change at 400 °C and 1000 °C were calculated. Kinetic analysis of Bi2S3 oxidation process was performed by Kissingers method in non-isothermal conditions.

scholarly journals Air-thermal oxidation of zirconium

2017 ◽  
Vol 1 (9) ◽  
Author(s):  
Zagorka Koneska ◽  
Ružica Manojlović ◽  
Dafinka Stoevska-Gogovska
Keyword(s):  
Weight Gain ◽  
Oxide Film ◽  
Thermal Oxidation ◽  
Raman Spectra ◽  
Metal Surface ◽  
Elevated Temperatures ◽  
Good Adhesion ◽  
Air Atmosphere ◽  
Micro Cracks ◽  
Parabolic Rate

Zirconium is one of those few metals which are capable of dissolving relativelylarge quantities of oxygen. When heated in air at elevated temperatures, anoxide layer is built up at the metal surface. The oxidation of mechanicallypolished zirconium was studied in the range 500-900oC in air atmosphere, attemperature intervals of 100oC, for exposure times from 5 min to 1860 min foreach temperature. The weight gain of the oxidized species was the reactedamount of oxygen with zirconium for the formation of the ZrO2. The weight gainand thickness of the oxide film increase with the increasing of the oxidation timeand temperature. The oxidation initially followed a parabolic rate at alltemperatures. At temperatures higher than 700oC oxide “breakaway” appears atthe longest oxidation times. Microstructural investigations have shown that theoxide layers are compact and with good adhesion to the metal surface, but attemperatures over 700oC, radial micro-cracks appear. Raman spectra of theformed oxides at the investigated temperatures are characteristic for monoclinicphase.

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