Structure and Phase Transformations in High Nitrogen and High Interstitial Steels of Different Alloying Systems - Short Review

2021 ◽  
Vol 410 ◽  
pp. 167-172
Author(s):  
Vera V. Berezovskaya ◽  
Eugeny A. Merkushkin ◽  
Ksenia A. Mamchits
Keyword(s):  
Phase Transformations ◽  
Light And Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Short Review ◽  
Austenitic Steels ◽  
Structure Evolution ◽  
X Ray Diffraction ◽  
High Nitrogen ◽  
Corrosion Properties ◽  
Excess Phases

The features of the structure evolution under thermal effect of Cr, Cr-Ni, Cr-Ni-Mn, and Cr-Mn-austenitic stainless steels with high nitrogen content and a total high content of carbon and nitrogen are analyzed. When studying the structure, we used light and electron microscopy, X-ray diffraction, dilatometry analysis and electrical resistance measurements. Fine structure and aging processes of austenite, nature and morphology of excess phases, as well as character of phase transformations and their relationship with the properties of steels have been studied. It is shown that Cr-Mn-steels with a high content of (C + N), having a homogeneous structure of austenite without excess phases, surpass Cr-Ni austenitic steels in mechanical and corrosion properties, have higher process ability than Cr-Mn-N-steel and are comparable with them in mechanical properties.

Structure Formation in High-Nitrogen Steel during Heat Treatment

2018 ◽  
Vol 284 ◽  
pp. 447-454 ◽  
Author(s):  
Vera V. Berezovskaya ◽  
Eugeny A. Merkushkin ◽  
Yu. A. Raskovalova
Keyword(s):  
Heat Treatment ◽  
Plastic Deformation ◽  
Light And Electron Microscopy ◽  
Austenitic Steels ◽  
X Ray Diffraction ◽  
High Nitrogen ◽  
Subsequent Aging ◽  
Hot Plastic Deformation ◽  
Nitrogen Steel ◽  
Χ Phase

Steel 06Cr18Mn19Mo2N (P900N + Mo) was chosen to study the phase composition and structural transformations occurring in high-nitrogen nickel-free austenitic steels as a result of heat treatments to which they are exposed during production or operation. The methods of light and electron microscopy, X-ray diffraction and dilatometric analysis were used in the work. The heat treatment scheme included hot plastic deformation, quenching and aging over a wide temperature range. It is shown that after the hot plastic deformation and quenching from 1050-1150 °С, and also after quenching with subsequent aging at 300 and 500 °С, the structure consists of austenite and isostructural matrix of nanoscale nitrides CrN. Thermal aging of steel at 700-750 °C causes the formation of Mo2N nitrides along the grain boundaries, and at 800 °C the decomposition of austenite is accompanied by a discontinuous reaction γγdepleted + σ with the formation of the χ-phase at prolonged exposures.

Laser Welded Joints of High-Nitrogen Austenitic Steels: Microstructure and Properties

2018 ◽  
Vol 284 ◽  
pp. 344-350 ◽  
Author(s):  
Vera V. Berezovskaya ◽  
A.V. Berezovskiy ◽  
D.H. Hilfi
Keyword(s):  
Welded Joints ◽  
Carbon Dioxide Laser ◽  
Continuous Wave ◽  
High Strength ◽  
Tensile Tests ◽  
Wave Mode ◽  
Austenitic Steels ◽  
Maximum Output ◽  
High Nitrogen ◽  
Corrosion Properties

High nitrogen austenitic steels are used as structural materials required possessing high strength and fracture toughness. The present study is concerned with the characteristic features (shape, size, properties and structure) of the laser welded joints in Cr-Mn-, Cr-Mn-Mo-high nitrogen steels compared to the ones of Cr-Ni-steel joint. Butt welded joints were made using carbon dioxide laser with a maximum output of 5 kW in the continuous wave mode. The hardness and tensile tests of welded joints in the air and 3.5 vol.%-solution of NaCl, as well as the theoretical studies were carried out by optical and transmission electron microscopy (TEM). The results are achieved by testing that the welded joints of HNS had satisfactory weldability, adequately high mechanical and corrosion properties. The austenite of the investigated HNS retains high stability throughout the welding cycle.

scholarly journals Formation and reversion of strain induced martensite on Fe-Cr-Ni alloys

2013 ◽  
Vol 66 (2) ◽  
pp. 221-225 ◽  
Author(s):  
Gabriela Lujan Brollo ◽  
Paulo Roberto Mei
Keyword(s):  
Metastable Phase ◽  
Cold Deformation ◽  
Austenitic Stainless Steels ◽  
Austenitic Steels ◽  
X Ray Diffraction ◽  
Ni Alloys ◽  
Wide Range ◽  
High Nickel ◽  
Strain Induced Martensite ◽  
Incoloy 800

Austenitic stainless steels represent a significant portion of the alloys used in the aeronautical, chemical, shipbuilding, food processing and biomechanical industries. They combine good mechanical properties with high corrosion resistance. When subjected to cold deformation, these steels exhibit a metastable phase called: strain induced martensite (ferromagnetic), whose formation increases mechanical strength and formability, allowing for a wide range of applications. Heated from room temperature, the strain induced martensite transforms to austenite (non-magnetic). It is easy to find information in literature about the strain induced martensite for 18Cr/8Ni austenitic steels, but there is no data for high nickel alloys like A286 (26Ni, 15Cr), Incoloy 800 (30-40 Ni, 21Cr) and Inconel (50Ni, 19Cr). Therefore, this study aimed to verify the formation of strain induced martensite after cold working in Fe-18Cr base alloys with the addition of up to 60 %Ni. The reversion of this phase to austenite after annealing up to 600 ºC was also studied. Optical microscopy, magnetic characterization tests, and x-ray diffraction were used to analyze the transformations.

Metal Injection Molding of Nickel-Free Austenitic Stainless-Steels I-Manufacturing Process

2007 ◽  
Vol 26-28 ◽  
pp. 15-18
Author(s):  
Yoshikazu Kuroda ◽  
Midori Komada ◽  
Ryo Murakami ◽  
Shingo Fukumoto ◽  
Noriyuki Tsuchida ◽  
...  
Keyword(s):  
Injection Molding ◽  
Austenitic Stainless Steels ◽  
High Strength ◽  
Austenitic Steels ◽  
Metal Injection Molding ◽  
High Nitrogen ◽  
Molding Method ◽  
Combined Use ◽  
Work Hardening Rate ◽  
Near Net Shape

Ni-free austenitic steels containing high nitrogen have been developed to protect against earth resource. High nitrogen steels (HNS) have a lot of advantages, e.g., HNS have high strength, corrosion resistance, toughness, work hardening rate and large rocking parameter in the Hall-Petch equation. On the other hand, it is difficult to fabricate HNS by IM method under 0.1 MPa and to work at room temperature. We have tried to make HNS by combined use of metal injection molding method (MIM) and nitrogen absorption method. Powder compositions used was Fe-17Cr-12Mn-3Mo.The benefit of this method is to make metal parts in near net shape. In order to use this method, we should know the sintering heat schedule, timing for introducing nitrogen gas, gas pressure and setter material etc. Therefore, the shrinkage rate, density and the solution-treated microstructure of MIM compacts were examined to find out the optimum conditions.

scholarly journals Machine learning augmented predictive and generative model for rupture life in ferritic and austenitic steels

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Osman Mamun ◽  
Madison Wenzlick ◽  
Arun Sathanur ◽  
Jeffrey Hawk ◽  
Ram Devanathan
Keyword(s):  
Pearson Correlation ◽  
Rupture Life ◽  
Model Performance ◽  
Austenitic Stainless Steels ◽  
Generative Model ◽  
Austenitic Steels ◽  
Gradient Boosting ◽  
Variational Autoencoder ◽  
Feature Importance ◽  
Boosting Algorithm

AbstractThe Larson–Miller parameter (LMP) offers an efficient and fast scheme to estimate the creep rupture life of alloy materials for high-temperature applications; however, poor generalizability and dependence on the constant C often result in sub-optimal performance. In this work, we show that the direct rupture life parameterization without intermediate LMP parameterization, using a gradient boosting algorithm, can be used to train ML models for very accurate prediction of rupture life in a variety of alloys (Pearson correlation coefficient >0.9 for 9–12% Cr and >0.8 for austenitic stainless steels). In addition, the Shapley value was used to quantify feature importance, making the model interpretable by identifying the effect of various features on the model performance. Finally, a variational autoencoder-based generative model was built by conditioning on the experimental dataset to sample hypothetical synthetic candidate alloys from the learnt joint distribution not existing in both 9–12% Cr ferritic–martensitic alloys and austenitic stainless steel datasets.

Stacking Faults in a High Nitrogen Face-Centered-Cubic Phase Formed on Nitrogen-Modified Austenitic Stainless Steel

2008 ◽  
Vol 373-374 ◽  
pp. 318-321
Author(s):  
J. Liang ◽  
M.K. Lei
Keyword(s):  
Stainless Steel ◽  
Plasma Source ◽  
Peak Shift ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
High Nitrogen ◽  
X Ray ◽  
Peak Asymmetry ◽  
Face Centered

Effects of stacking faults in a high nitrogen face-centered-cubic phase (γΝ) formed on plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel on peak shift and peak asymmetry of x-ray diffraction were investigated based on Warren’s theory and Wagner’s method, respectively. The peak shift from peak position of the γΝ phase is ascribed to the deformation faults density α, while the peak asymmetry of the γΝ phase is characterized by deviation of the center of gravity of a peak from the peak maximum (Δ C.G.) due to the twin faults density β. The calculated peak positions of x-ray diffraction patterns are consistent with that measured for plasma source ion nitrided 1Cr18Ni9Ti stainless steel.

Full-field X-ray diffraction microscopy using polymeric compound refractive lenses

2014 ◽  
Vol 47 (6) ◽  
pp. 1882-1888 ◽  
Author(s):  
J. Hilhorst ◽  
F. Marschall ◽  
T. N. Tran Thi ◽  
A. Last ◽  
T. U. Schülli
Keyword(s):  
Imaging Techniques ◽  
Light And Electron Microscopy ◽  
Added Value ◽  
Acquisition Time ◽  
Imaging Method ◽  
X Ray Diffraction ◽  
Polymeric Compound ◽  
Full Field ◽  
X Ray ◽  
Diffraction Imaging

Diffraction imaging is the science of imaging samples under diffraction conditions. Diffraction imaging techniques are well established in visible light and electron microscopy, and have also been widely employed in X-ray science in the form of X-ray topography. Over the past two decades, interest in X-ray diffraction imaging has taken flight and resulted in a wide variety of methods. This article discusses a new full-field imaging method, which uses polymer compound refractive lenses as a microscope objective to capture a diffracted X-ray beam coming from a large illuminated area on a sample. This produces an image of the diffracting parts of the sample on a camera. It is shown that this technique has added value in the field, owing to its high imaging speed, while being competitive in resolution and level of detail of obtained information. Using a model sample, it is shown that lattice tilts and strain in single crystals can be resolved simultaneously down to 10−3° and Δa/a= 10−5, respectively, with submicrometre resolution over an area of 100 × 100 µm and a total image acquisition time of less than 60 s.

Influence of Phase Transformations on Residual Stresses in Welded Structures

2013 ◽  
Author(s):  
R. J. Dennis ◽  
R. Kulka ◽  
O. Muransky ◽  
M. C. Smith
Keyword(s):  
Phase Transformation ◽  
Residual Stresses ◽  
Phase Transformations ◽  
Numerical Models ◽  
Material Model ◽  
Transformation Model ◽  
Austenitic Steels ◽  
Beam Specimen ◽  
Welded Structures ◽  
The Impact

A key aspect of any numerical simulation to predict welding induced residual stresses is the development and application of an appropriate material model. Often significant effort is expended characterising the thermal, physical and hardening properties including complex phenomena such as high temperature annealing. Consideration of these aspects is sufficient to produce a realistic prediction for austenitic steels, however ferritic steels are susceptible to solid state phase transformations when heated to high temperatures. On cooling a reverse transformation occurs, with an associated volume change at the isothermal transformation temperature. Although numerical models exist (e.g. Leblond) to predict the evolution of the metallurgical phases, accounting for volumetric changes, it remains a matter of debate as to the magnitude of the impact of phase transformations on residual stresses. Often phase transformations are neglected entirely. In this work a simple phase transformation model is applied to a range of welded structures with the specific aim of assessing the impact, or otherwise, of phase transformations on the magnitude and distribution of predicted residual stresses. The welded structures considered account for a range of geometries from a simple ferritic beam specimen to a thick section multi-pass weld. The outcome of this work is an improved understanding of the role of phase transformation on residual stresses and an appreciation of the circumstances in which it should be considered.

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