scholarly journals Matematical modeling of the process of enlarging the austenitic grain during high-temperature heating of alloy structural steel

2019 ◽  
pp. 74-84
Author(s):  
V. A. Kukareko ◽  
B. M. Gatsuro ◽  
A. N. Grigorchik ◽  
A. N. Chichin
Keyword(s):  
High Temperature ◽  
Heating Rate ◽  
Grain Structure ◽  
Slow Heating ◽  
Case Hardening ◽  
Regression Equations ◽  
Impurity Atoms ◽  
Average Size ◽  
Case Hardening Steel

The influence of the heating rate of a typical case hardening steel 15KHGN2TA and 25KHGT on the growth of austenitic grain during long-term isothermal exposures at the high-temperature chemical-heat treatment was studied. It is shown that the change in the rate of heating case hardening steels in the temperature interval a®g transformations during chemical-thermal treatment has a significant impact on the process of growth of austenitic grains in them.Regression equations describing the dependence of the average size of austenitic grain on the heating rate, pre-annealing temperature and cementation temperature are obtained, which allow selecting the cementation modes of various steels. A phenomenological model describing the mechanism of formation and growth of austenitic grains in steels under heating at different speeds is developed.It is concluded that the slow heating of steels in the interval of phase a®g transformation contributes to the formation of a complex of small austenite grains separated by high angle boundaries with adsorbed on them by impurity atoms, which ensures higher resistance grain structure to coalescence and reduce the rate of migration of the boundaries during prolonged hightemperature austenization.

scholarly journals The influence of the heating rate of cemented constructional steels on the growth of austenitic grain in the process of high-temperature holding

2019 ◽  
Vol 63 (4) ◽  
pp. 399-406 ◽  
Author(s):  
V. A. Kukareko ◽  
A. L. Valko ◽  
A. N. Chichin
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Thermal Treatment ◽  
Grain Boundaries ◽  
Grain Structure ◽  
Slow Heating ◽  
Experimental Conditions ◽  
Impurity Atoms ◽  
High Temperature Aging ◽  
Temperature Aging

The influence of the heating mode of samples of constructional cemented steels 20ХН3А, 20ХГНР and 15ХГН2ТА on the value of austenite grain after high-temperature isothermal aging at 1000 °С is studied. It is shown that the heating of steels at a rate of 1.2–3.0 °C / min in the phase-transformation interval stabilizes the grain structure of the steels and leads to a slowing down of the kinetics of the growth of austenite grains during prolonged high-temperature aging, which makes it possible to increase the temperature of the chemical-thermal treatment of steels. It is concluded that the stabilization of the grain structure of steels is associated with the formation of segregation of impurity atoms and particles at grain boundaries with high-angle disorientation during slow heating, which prevents migration of grain boundaries in the process of prolonged high-temperature aging. A high-temperature chemical-thermal treatment of a batch of billets from steel 20ХН3А under experimental conditions with stepwise heating in the phase-transformation interval provided a qualitative fine-grained structure of the cemented layer.

Development and Evaluation of Nanostructured Coatings for Long-Term Corrosion and Oxidation Performance

2010 ◽  
Author(s):  
Madhavrao Govindaraju ◽  
N. Sastry Cheruvu ◽  
Ken Natesan
Keyword(s):  
High Temperature ◽  
Coal Ash ◽  
Microstructural Characterization ◽  
Grain Structure ◽  
Temperature Oxidation ◽  
Al Content ◽  
Fine Grain ◽  
Nano Crystalline ◽  
Oxidation Performance

Nanocrystalline coatings were developed on austenitic alloys to meet the high temperature oxidation and corrosion requirements of the waterwalls and superheater/reheater sections of ultra-supercritical (USC) boilers. Nanocoatings were deposited on 304 stainless steels alloys using Plasma Enhanced Magnetron Sputtering (PEMS) process. Coatings of Fe-18Cr-8Ni-xAl (where x = 0, 4, 10%) were deposited on all 304L steel substrates. The as-deposited Fe-based nano-crystalline coatings exhibited ultra-fine grain structure. The long-term oxidation behavior of nanocrystalline coatings was evaluated through cyclic oxidation tests. The results showed that the fine grain structure improved oxidation resistance, promoted selective oxidation of Cr or Al. High temperature corrosion tests were performed in simulated combustion and gasification environment with and without the presence of deposits such as coal ash, alkali sulfates, and sodium chloride. The weight loss or gain for the exposed samples was measured followed by microstructural characterization. Exposed samples were sectioned and characterized by energy dispersive x-ray analysis to identify the corrosion-product phases in the specimen scales. The results highlighted the importance of bonding between the coating and base alloys to resist the coal ash corrosion. Increasing amount of Al content is required to resist sulfur corrosion. Evaluation of samples tested in flue gas environment with SO2 showed an increase in corrosion resistance with increase in aluminum content in the coating.

scholarly journals Sliding Wear Behavior of High-Temperature Vacuum-Brazed WC-Co-NiP Functional Composite Coatings

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 88
Author(s):  
Roxana Muntean ◽  
Dragoș-Toader Pascal ◽  
Norbert Kazamer ◽  
Gabriela Mărginean ◽  
Viorel-Aurel Șerban
Keyword(s):  
High Temperature ◽  
Sliding Wear ◽  
Wear Behavior ◽  
Composite Coatings ◽  
Dry Sliding Wear ◽  
Case Hardening ◽  
Functional Coatings ◽  
Wear Rates ◽  
The Coefficient Of Friction ◽  
Case Hardening Steel

The present study aimed to investigate the tribological behavior of high-temperature vacuum-brazed WC-Co-NiP functional coatings deposited on 16MnCr5 case hardening steel. Dry sliding wear resistance was evaluated using a non-conformal ball-on-disk arrangement, at room temperature against 100Cr6 and WC-Co static partners, respectively. Morphological, microstructural, and chemical composition analyses showed a complex, phased structure composed of tungsten carbide, nickel, and hard cobalt-based η-structure. In the testing conditions, the coefficient of friction against 100Cr6 and WC-Co counterparts entered a steady-state value after approximately 1000 m and 400 m, respectively. The wear track analysis revealed phenomena of particles trapped between the sliding bodies, as well as gradual removal of asperities. The calculations of the wear rates proved that the values were strongly influenced by properties of the sliding system, such as crystal structure, stress discontinuities, hardness, and material homogeneity.

scholarly journals Effects of Concentrations of Micro-alloying Elements and Hot-forging Temperature on Austenite Grain Structure Formed during Carburization of Case-hardening Steel

2020 ◽  
Vol 60 (11) ◽  
pp. 2549-2557
Author(s):  
Genki Saito ◽  
Norihito Sakaguchi ◽  
Munekazu Ohno ◽  
Kiyotaka Matsuura ◽  
Masayoshi Takeuchi ◽  
...  
Keyword(s):  
Hot Forging ◽  
Alloying Elements ◽  
Grain Structure ◽  
Case Hardening ◽  
Austenite Grain ◽  
Case Hardening Steel

scholarly journals Mechanisms of the Reverse Martensite-to-Austenite Transformation in a Metastable Austenitic Stainless Steel

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 599
Author(s):  
Dmitrii Panov ◽  
Egor Kudryavtsev ◽  
Ruslan Chernichenko ◽  
Aleksandr Smirnov ◽  
Nikita Stepanov ◽  
...  
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Austenitic Stainless Steel ◽  
Grain Structure ◽  
Slow Heating ◽  
Continuous Heating ◽  
Ultrafine Grain ◽  
Medium Temperature ◽  
Average Grain Size ◽  
Metastable Austenitic Stainless Steel

The martensite-to-austenite reversion mechanisms under continuous heating and annealing of metastable austenitic stainless steel subjected to cold swaging were studied. The reversion-temperature-time diagram was constructed using high-resolution dilatometry. The diagram revealed a sequence of martensitic and diffusional reversion and recrystallization. Martensitic and diffusional reversion might be separated by using the heating rate of >10 °C/s. The reversion started via the martensitic mechanism, and the diffusional mechanism developed during subsequent heating. However, both mechanisms enhance simultaneously during continuous heating at slow heating rates (<10 °C/s). At higher temperatures, recrystallization occurred. Post-mortem microstructure analysis has allowed classifying the reverse annealing modes into low- (500–650 °C), medium- (~700 °C), and high-temperature (~800 °C) regimes. During low-temperature annealing, the development of the phase reversion, recovery, recrystallization, and carbide precipitation was characterized by both a high amount of new austenite grains and restriction of their growth that resulted in the formation of an ultrafine grain structure with an average grain size of 100–200 nm. Medium-temperature annealing was associated with the formation of almost a fully recrystallized austenitic structure, but the lamellar regions were still detected. Austenitic grain growth and dissolution of carbide particles were enhanced during high-temperature annealing.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

KUBOTA KNC-03

Alloy Digest ◽  
2010 ◽  
Vol 59 (1) ◽  
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
High Strength ◽  
Temperature Performance ◽  
Resistance To Oxidation

Abstract Kubota KNC-03 is a grade with a combination of high strength and excellent resistance to oxidation. These properties make this alloy suitable for long-term service at temperature up to 1250 deg C (2282 deg F). This datasheet provides information on physical properties, hardness, elasticity, tensile properties, and compressive strength as well as creep. It also includes information on high temperature performance as well as casting and joining. Filing Code: Ni-676. Producer or source: Kubota Metal Corporation, Fahramet Division. See also Alloy Digest Ni-662, April 2008.

AISI 4320

Alloy Digest ◽  
1959 ◽  
Vol 8 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Physical Properties ◽  
Heat Treating ◽  
Case Hardening ◽  
High Toughness ◽  
Nickel Chromium ◽  
Steel Mills ◽  
Shock Resistance ◽  
Case Hardening Steel

Abstract AISI 4320 is a nickel-chromium-molybdenum case hardening steel having high toughness and shock resistance. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SA-80. Producer or source: Alloy steel mills and foundries.

AISI 8615

Alloy Digest ◽  
1965 ◽  
Vol 14 (7) ◽  
Keyword(s):  
Fracture Toughness ◽  
Alloy Steel ◽  
Heat Treating ◽  
Case Hardening ◽  
Low Carbon ◽  
Heavy Duty ◽  
Core Strength ◽  
Nickel Chromium ◽  
Steel Mills ◽  
Case Hardening Steel

Abstract AISI 8615 is a low-carbon, nickel-chromium-molybdenum alloy steel capable of producing high core strength and toughness. It is a case hardening steel recommended for heavy duty gears, cams, shafts, chains, fasteners, piston pins, etc. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, machining, and joining. Filing Code: SA-180. Producer or source: Alloy steel mills and foundries.

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