scholarly journals IMPACT OF USE ON RELEASE PROCESSES IN AUSTENITIC STEEL TP347HFG

2021 ◽  
Vol 72 (4) ◽  
pp. 22-26
Author(s):  
Hanna Purzyńska ◽  
Grzegorz Golański ◽  
Michał Kwiecień ◽  
Dariusz Paryż
Keyword(s):  
Grain Boundaries ◽  
Austenitic Steel ◽  
M23c6 Carbide ◽  
Σ Phase ◽  
Precipitation Processes ◽  
Austenite Grains ◽  
Carbide Particles ◽  
M23c6 Carbides ◽  
Large Primary ◽  
Release Processes

The article presents an analysis of precipitation processes in heat-resistant TP347HFG steel after 41,000 h of operation at 585°C. Microstructure investigation showed that the use of the tested steel resulted mainly in the precipitation processes occurring at grain boundaries. Identification of the precipitates showed the presence of M23C6 carbides and σ phase particles along boundaries. Single M23C6 carbide particles were revealed also at twin boundaries. Inside austenite grains, apart from large, primary precipitates, finely-dispersed secondary NbX particles (X = C,N) were also observed.

scholarly journals On the M23C6-Carbide in 2205 Duplex Stainless Steel: An Unexpected (M23C6/Austenite)—Eutectoid in the δ-Ferritic Matrix

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1340
Author(s):  
Abdelkrim Redjaïmia ◽  
Antonio Manuel Mateo Garcia
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Geometrical Model ◽  
The Other ◽  
M23c6 Carbide ◽  
Interface Plane ◽  
Orientation Relationships ◽  
Ferritic Matrix ◽  
Σ Phase ◽  
M23c6 Carbides

This study is focused on isothermal and anisothermal precipitation of M23C6 carbides from the fully ferritic structure of the (γ + δ) austenitic-ferritic duplex stainless steel X2CrNiMo2253, (2205). During isothermal heat treatments, small particles of K-M23C6 carbide precipitates at the δ/δ grain-boundaries. Their formation precedes γ and σ-phases, by acting as highly potential nucleation sites, confirming the undertaken TEM investigations. Furthermore, anisothermal heat treatment leads to the formation of very fine islands dispersed throughout the fully δ-ferritic matrix. TEM characterization of these islands reveals a particular eutectoid, reminiscent of the well-known (γ-σ)—eutectoid, usually encountered in this kind of steel. TEM and electron microdiffraction techniques were used to determine the crystal structure of the eutectoid constituents: γ-Austenite and K-M23C6 carbides. Based on this characterization, orientation relationships between the two latter phases and the ferritic matrix were derived: cube-on-cube, on one hand, between K-M23C6 and γ-Austenite and Kurdjumov-Sachs, on the other hand, between γ-Austenite and the δ-ferritic matrix. Based on these rational orientation relationships and using group theory (symmetry analysis), the morphology and the only one variant number of K-M23C6 in γ-Austenite have been elucidated and explained. Thermodynamic calculations, based on the commercial software ThermoCalq® (Thermo-Calc Software, Stockholm, Sweden), were carried out to explain the K-M23C6 precipitation and its effect on the other decomposition products of the ferritic matrix, namely γ-Austenite and σ-Sigma phase. For this purpose, the mole fraction evolution of K-M23C6 and σ-phase and the mass percent of all components entering in their composition, have been drawn. A geometrical model, based on the corrugated compact layers instead of lattice planes with the conservation of the site density at the interface plane, has been proposed to explain the transition δ-ferrite ⇒ {γ-Austenite ⇔ K-M23C6}.

Microstructural Stability of Alloy 617 Mod. During Thermal Aging

2014 ◽  
Author(s):  
Guo Yan ◽  
Zhou Rongcan ◽  
Tang Liying ◽  
Hou Shufang ◽  
Wang Bohan
Keyword(s):  
Grain Boundaries ◽  
Precipitation Hardening ◽  
Aged Alloy ◽  
Microstructural Stability ◽  
Absorbed Energy ◽  
Alloy 617 ◽  
The Impact ◽  
Carbide Particles ◽  
M23c6 Carbides ◽  
Intragranular Carbide

The microstructural stability of Alloy 617 mod. during aging for up to 3000 h at temperatures of 700°C and 750°C was investigated. The precipitates of the aged alloy included M23C6 carbides located both inside grains (intragranular) and at grain boundaries (intergranular) and γ′ phase dispersed within grains. During aging, the intergranular precipitates showed a good stability. Intragranular particles increased substantially after the aging for 3000h at 750°C. Inter and intragranular carbide particles resulted in the precipitation hardening of the aged alloys. The precipitation of γ′ phase particles during aging at 700°C and 750°C is also an important factor for an enhanced hardness and an obvious decrease of the impact absorbed energy. Additionally, the intergranular cracks apparently lead to a decrease in the impact absorbed energy for the aged alloys due to carbide particles at grain boundaries. The impact absorbed energies of the aged alloys were fairly stable within the dwelling time from 300 h to 3000 h and were in the range of 63∼65J and 75∼83J for the 700°C and 750°C aging, respectively. Paper published with permission.

Image Evaluation of Distribution of Carbide Particles in Repeatedly Quenched (Two and Three Times) JIS-SUJ2 Steels

2021 ◽  
Vol 315 ◽  
pp. 66-71
Author(s):  
Koshiro Mizobe ◽  
Takahiro Matsueda ◽  
Yoshinobu Miyabe ◽  
Katsuyuki Kida
Keyword(s):  
Prior Austenite ◽  
Optimal Distribution ◽  
Image Evaluation ◽  
Austenite Grains ◽  
Carbide Particles

In order to investigate the relation between prior austenite grains (PAG) and the carbide particles, we observed etched microstructure in JIS-SUJ2 steel. We traced and drew the outlines of carbide particles and analyzed some of their shape values. We confirmed that the repeated quenching can refine PAG size while keeping the optimal distribution of the carbide particles.

scholarly journals Mechanical, structural and tribological properties of superaustenitic stainless steel submitted at solution heat treatment

2015 ◽  
Vol 20 (1) ◽  
pp. 160-168 ◽  
Author(s):  
Fabiana Cristina Nascimento Borges ◽  
Willian Rafael de Oliveira ◽  
Jonas Kublitski
Keyword(s):  
Stainless Steel ◽  
Austenitic Steel ◽  
Instrumented Indentation ◽  
X Ray Diffraction ◽  
Superaustenitic Stainless Steel ◽  
Space Group ◽  
X Ray ◽  
Σ Phase ◽  
Bulk Data ◽  
Corrosive Environments

The superaustenitic stainless steel presents several technological applications, mainly in corrosive environments. The different phase precipitation might alter some of its mechanical properties. Such alterations affect several factors, including the working life of the material under adverse working conditions. In this study, Instrumented Indentation techniques, Tribology and X-ray diffraction (XRD) were used to evaluate alterations in regions close to the surface. The parameters analyzed were: hardness and elastic modulus (instrumented indentation), friction coefficient (tribology) and structural alterations of the unit cell of the identified phases (XRD - Rietveld Refinement). All properties analyzed were compared with those of common austenitic steel. The presence of σ-phase (space group P42mnm) and γ-austenite (space group Fm3m) were detected. Data analyzed indicated that the presence of σ-phase caused small alteration in properties such as hardness in regions close to the surface. In the regions farther from the surface (material bulk) data can be compared to that of conventional austenitic steel.

scholarly journals Study on σ Phase in Fe–Al–Cr Alloys

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1092 ◽  
Author(s):  
Jintao Wang ◽  
Shouping Liu ◽  
Xiaoyu Han
Keyword(s):  
Mechanical Properties ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Thermodynamic Calculation ◽  
Second Phase ◽  
Σ Phase ◽  
Austenitic Transformation ◽  
The Matrix ◽  
The Relationship

In this paper, a method of using the second phase to control the grain growth in Fe–Al–Cr alloys was proposed, in order to obtain better mechanical properties. In Fe–Al–Cr alloys, austenitic transformation occurs by adding austenitizing elements, leading to the formation of the second phase and segregation at the grain boundaries, which hinders grain growth. FeCr(σ) phase was obtained in the Fe–Al–Cr alloys, which had grains of several microns and was coherent and coplanar with the matrix (Fe2AlCr). The nucleation of σ phase in Fe–Al–Cr alloy was controlled by the ratio of nickel to chromium. When the Ni/Cr (eq) ratio of alloys was more than 0.19, σ phase could nucleate in Fe–Al–Cr alloy. The relationship between austenitizing and nucleation of FeCr(σ) phase was given by thermodynamic calculation.

scholarly journals Microstructure and Mechanical Properties of 4Al Alumina-Forming Austenitic Steel after Cold-Rolling Deformation and Annealing

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2767 ◽  
Author(s):  
Chenchen Jiang ◽  
Qiuzhi Gao ◽  
Hailian Zhang ◽  
Ziyun Liu ◽  
Huijun Li
Keyword(s):  
Grain Size ◽  
Cold Rolling ◽  
Grain Boundaries ◽  
Austenitic Steel ◽  
Rolling Reduction ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Cold Rolling Reduction ◽  
Average Grain Size ◽  
Cold Rolled

Microstructural evolutions of the 4Al alumina-forming austenitic steel after cold rolling with different reductions from 5% to 30% and then annealing were investigated using electron backscattering diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile properties and hardness were also measured. The results show that the average grain size gradually decreases with an increase in the cold-rolling reduction. The low angle grain boundaries (LAGBs) are dominant in the cold-rolled samples, but high angle grain boundaries (HAGBs) form in the annealed samples, indicating that the grains are refined under the action of dislocations. During cold rolling, high-density dislocations are initially introduced in the samples, which contributes to a large number of dislocations remaining after annealing. With the sustaining increase in cold-rolled deformation, the samples exhibit more excellent tensile strength and hardness due to the decrease in grain size and increase in dislocation density, especially for the samples subjected to 30% cold-rolling reduction. The contribution of dislocations on yield strength is more than 60%.

scholarly journals The Role of Deformation in Coarsening of M23C6 Carbide Particles in 9% Cr Steel

2020 ◽  
Vol 121 (8) ◽  
pp. 804-810
Author(s):  
E. S. Tkachev ◽  
A. N. Belyakov ◽  
R. O. Kaibyshev
Keyword(s):  
M23c6 Carbide ◽  
Carbide Particles

Effect of N Content on Mechanical Properties and Microstructure of Alloy 690

2009 ◽  
Author(s):  
Kui Liu ◽  
Xianchao Hao ◽  
Ming Gao ◽  
Shuo Li ◽  
Yiyi Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Boundaries ◽  
Room Temperature ◽  
N Content ◽  
Solution Treated ◽  
Alloy 690 ◽  
Significant Difference ◽  
Tension Testing ◽  
Austenite Grains ◽  
Reduction In Area

The microstructures and mechanical properties of nitrogen bearing Alloy 690 have been systematically investigated. Alloy ingots with different N addition, range from 38 to 330wt.ppm, were melted using vacuum induction melting (VIM) plus electro-slag re-melting (ESR) double processing techniques. The forged and hot rolled different N content bars were solid solution treated between 1010°C and 1080°C, thermally treated at 715°C for different state mechanical property testing and microstructure study. Microstructure analysis indicated that nitrogen addition to Alloy 690 can effectively refine the solution treated austenite grains. This may be associated with titanium nitrides pinning the grain boundaries and hindering the grain growth during solid solution treatment. More nitrides, which are identified as TiN, were found on the grain boundaries and in the inside of austenite grains with increasing N contents of the alloy. The carbide precipitation at 715°C showed significant difference identified by SEM. At the level of 38, 100 and 220wt.ppm N, the chromium carbide Cr23C6 distribution on the grain boundaries appeared to be semi-continuous; when the N content reached 330wt.ppm, only few discrete type of carbides were observed. The tension testing results at room temperature of different N content alloys proved that both the ultimate tensile strength (UTS) and the yield strength (YS) enhanced about 50MPa when N content was raised from 38 to 330wt.ppm in this alloy; while the corresponding elongation (EL) and reduction in area (RA) adversely dropped about 5%. Room temperature hardness rose with increasing N content, well matched tensile strength. High temperature tension testing results at the range of 900∼1250°C showed that a severely hot ductility dip, representing by the values of the reduction in area (RA), existed in 300wt.ppm and 100wt.ppm nitrogen containing alloys at the lower end temperature range of 950∼1100°C. However, such ductility dip could be improved when the N content was at 220wt.ppm, and completely eliminated at 38wt.ppm N content. At the higher end temperature rang of 1150∼1250°C, the ductility of all 4 nitrogen bearing alloys did not show significant difference, even though the hot ductility of minimum 38wt.ppm N samples was preferable. Nitrogen content did not affect high temperature strength; the UTS values nearly had no change at the same testing temperature with different nitrogen bearing alloys. The carbide precipitation difference of the thermally treated alloy, induced by N addition, may affect Alloy 690 corrosion properties, which needs to be studied in future. The mechanical properties variation both at room temperature and high temperatures of different nitrogen bearing alloys in this study will be certainly beneficial to determine the practical processing routes of Alloy 690.

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