Prediction of phase distribution and chemical composition during gas carburizing of stainless steels

2004 ◽  
Vol 120 ◽  
pp. 249-257
Author(s):  
T. Turpin ◽  
J. Dulcy ◽  
M. Gantois
Keyword(s):  
Experimental Study ◽  
Stainless Steel ◽  
Chemical Composition ◽  
Phase Transformations ◽  
Stainless Steels ◽  
Phase Distribution ◽  
Carbon Profile ◽  
Reducing Gas ◽  
Gas Carburizing ◽  
Carburizing Process

This article reports a theoretical and experimental study aiming at reducing gas carburizing experiments on stainless steels. This work was carried out to show the advantages of numerical calculations to simulate phase transformations during the gas carburizing process of high alloyed steels. The use of Thermo-Calc and Dictra software allows the metallurgist to predict the optimum thermochemical and heat treatments which are necessary to obtain an accurate carbon profile in a stainless steel. Moreover, the phase distribution and chemical composition can be followed as a function of time and/or distance to gas-solid interface.

scholarly journals Stainless steel corrosion in instrumentation pipe

2019 ◽  
Vol 14 (40) ◽  
pp. 31-40
Author(s):  
Jean Victal do Nascimento ◽  
Rafael Adão de Carvalho ◽  
Davi Pereira Garcia ◽  
Rômulo Maziero ◽  
Edelize Angelica Gomes ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Chemical Composition ◽  
Austenitic Stainless Steel ◽  
Stainless Steels ◽  
Chloride Ions ◽  
Main Function ◽  
Marine Atmosphere ◽  
Steel Aisi ◽  
Aisi 316 ◽  
Stainless Steel Aisi

Corrosion, being a destructive process, causes damage in almost all industrial sectors. In this way, it is harmful both from an economic, social and, especially, safety point of view, as it can cause failures in critical equipment and components of an industrial process. At this point, stainless steels are considered the most corrosion resistant metals. The resistance depends on the chemical composition and microstructure, factors that directly influence the passivation of these materials. The resistance is proportionally related to the addition of chromium (Cr) to the mixture, as well as other alloying elements, among which is the molybdenum (Mo), whose main function is to maximize corrosion resistance in the marine atmosphere, as in case of austenitic stainless steel AISI 316 which presents in the chemical composition a percentage of the element Mo. Austenitic stainless steels are applied in instrumentation systems in tubing for reliability in severe atmospheres in accordance with ASTM A269 which establishes the materials applicable to this function. Thus, the present work presents, through a review and case study, Pitting Corrosion of tubings of austenitic stainless steel AISI 316 in the presence of chloride ions (Cl-) coming from the marine atmosphere. The results show that there is no change in the longitudinal and transverse structure for all analyzed tubes, showing a homogeneous austenitic structure, free of intergranular precipitations.

SCC growth rate measurements and surface oxide film characterization on high SFE austenitic stainless steels in a simulated BWR water environment

2014 ◽  
Vol 1715 ◽  
Author(s):  
S. Ooki ◽  
T. Yonezawa ◽  
M. Watanabe ◽  
H. Kokawa
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Chemical Composition ◽  
Oxide Film ◽  
Stainless Steels ◽  
Growth Rates ◽  
Oxidation Behavior ◽  
Water Environment ◽  
Austenitic Stainless Steels ◽  
Composition Control

ABSTRACTStress Corrosion Cracking (SCC) has been detected in Boiling Water Reactors (BWRs) on core shrouds and primary water re-circulation piping made of low carbon stainless steels. Material hardening strongly affects SCC propagation behavior, and SCC growth rates increase with increasing hardness of austenitic stainless steels caused by cold work or neutron irradiation.Research work has been conducted in the authors’ laboratories with the aim of improving SCC resistance using chemical composition control of stainless steels. It has been previously reported that high stacking fault energy (SFE) materials showed better SCC resistance than low SFE materials due to hardening being suppressed in high SFE materials. In the present study, SCC growth rate (CGR) tests were performed using 15% cold worked Types 316L and 25Cr-20Ni stainless steels in a simulated BWR water environment. The 25Cr-20Ni stainless steel used has high SFE value due to chemical composition control and measured SCC growth rates were lower than those of low SFE stainless steels.However, oxidation behavior is one of the more important factors influencing SCC of austenitic stainless steels in addition to material hardening behavior, and the influence of the chemical composition control necessary to increase SFE on oxidation behavior in BWR primary coolants is still unclear. In this study, therefore, immersion tests using Types 316L and 25Cr-20Ni stainless steel specimens were also conducted in the simulated BWR water environment. The surface oxide films on the specimens were then analyzed with micro-Raman spectroscopy and glow discharge optical emission spectroscopy in order to help clarify the oxidation behavior.The results of these tests and analyses showed that the NiFe2O4 content of the outer oxide layers on the high SFE stainless steels was higher than that on the low SFE stainless steels. The inner oxide film on the 25Cr-20Ni stainless steel also had a high chromium content.Based on the above results, SCC resistance and oxidation behavior of high SFE austenitic stainless steels in a simulated BWR water environment will be discussed.

Properties of Vacuum Sintered Duplex Stainless Steels

2006 ◽  
Vol 15-17 ◽  
pp. 828-833 ◽  
Author(s):  
Leszek Adam Dobrzański ◽  
Z. Brytan ◽  
Marco Actis Grande ◽  
Mario Rosso
Keyword(s):  
Stainless Steel ◽  
Powder Metallurgy ◽  
Chemical Composition ◽  
Austenitic Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Stainless Steels ◽  
Duplex Stainless Steels ◽  
Vacuum Furnace ◽  
Rapid Cooling ◽  
The Right

This work presents the possibility of obtaining duplex stainless steels through powder metallurgy technology starting from austenitic X2CrNiMo17-12-2, martensitic X6Cr13 powders by controlled addition of alloying elements, such as Cr, Ni, Mo, Cu in the right quantity to obtain the chemical composition of the structure similar to biphasic one. Moreover the ferritic stainless steel X6Cr17 has been mixed to austenitic stainless steel in the ratio of 50%-50% in order to exam the deriving structure after sintering. In the studies behind the preparation of mixes, Schaffler’s diagram was taken into consideration. Prepared mixes of powders have been compacted at 800 MPa and sintered in a vacuum furnace with argon backfilling at 1260°C for 1 hour; after sintering rapid cooling has been applied in N2.

Delta Ferrite Formation in Austenitic Stainless Steel Castings

2012 ◽  
Vol 730-732 ◽  
pp. 733-738 ◽  
Author(s):  
Angelo Fernando Padilha ◽  
Caio Fazzioli Tavares ◽  
Marcelo Aquino Martorano
Keyword(s):  
Stainless Steel ◽  
Chemical Composition ◽  
Cooling Rate ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Magnetic Method ◽  
Empirical Formulas ◽  
Delta Ferrite ◽  
Ferrite Formation ◽  
Steel Castings

The effects of chemical composition and cooling rate on the delta ferrite formation in austenitic stainless steels have been investigated. Ferrite fractions measured by a magnetic method were in the range of 0 to 12% and were compared with those calculated by empirical formulas available in the literature. The delta ferrite formation (amount and distribution) was strongly affected by the steel chemical composition, but less affected by the cooling rate. Among several formulas used to calculate the amount of delta ferrite, the best agreement was obtained with those proposed independently by Schneider and Schoefer, the latter being recommended in the ASTM 800 standard.

scholarly journals Stainless steel corrosion in instrumentation pipe

2019 ◽  
Vol 14 (40) ◽  
pp. 31-40
Author(s):  
Jean Victal do Nascimento ◽  
Rafael Adão de Carvalho ◽  
Davi Pereira Garcia ◽  
Rômulo Maziero ◽  
Edelize Angelica Gomes ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Chemical Composition ◽  
Austenitic Stainless Steel ◽  
Stainless Steels ◽  
Chloride Ions ◽  
Main Function ◽  
Marine Atmosphere ◽  
Steel Aisi ◽  
Aisi 316 ◽  
Stainless Steel Aisi

Corrosion, being a destructive process, causes damage in almost all industrial sectors. In this way, it is harmful both from an economic, social and, especially, safety point of view, as it can cause failures in critical equipment and components of an industrial process. At this point, stainless steels are considered the most corrosion resistant metals. The resistance depends on the chemical composition and microstructure, factors that directly influence the passivation of these materials. The resistance is proportionally related to the addition of chromium (Cr) to the mixture, as well as other alloying elements, among which is the molybdenum (Mo), whose main function is to maximize corrosion resistance in the marine atmosphere, as in case of austenitic stainless steel AISI 316 which presents in the chemical composition a percentage of the element Mo. Austenitic stainless steels are applied in instrumentation systems in tubing for reliability in severe atmospheres in accordance with ASTM A269 which establishes the materials applicable to this function. Thus, the present work presents, through a review and case study, Pitting Corrosion of tubings of austenitic stainless steel AISI 316 in the presence of chloride ions (Cl-) coming from the marine atmosphere. The results show that there is no change in the longitudinal and transverse structure for all analyzed tubes, showing a homogeneous austenitic structure, free of intergranular precipitations.

scholarly journals Activation and Repassivation of Stainless Steels in Artificial Brines as a Function of pH

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3811 ◽  
Author(s):  
Emir Mujanović ◽  
Bojan Zajec ◽  
Tadeja Kosec ◽  
Andraž Legat ◽  
Stefan Hönig ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Chemical Composition ◽  
Electrochemical Properties ◽  
Stainless Steels ◽  
Chemical Activation ◽  
Oil Wells ◽  
Ph Values ◽  
Hard Particles ◽  
Scratch Tests ◽  
Repassivation Kinetics

When planning oil wells with stainless steel components, two possible reasons for depassivation have to be considered—chemical depassivation caused by acidizing jobs and mechanical depassivation caused by various tools and hard particles. The study explores conditions causing chemical activation of investigated steels and circumstances under which repassivation occurs after activation. The main focus of the study is to determine, how quickly various steels can repassivate under different conditions and to find pH values where repassivation will occur after depassivation. The investigated steels were ferritic (martensitic or bainitic) in the cases of 13Cr, 13Cr6Ni2Mo, and 17Cr4Ni2Mo, austenitic in the case of 17Cr12Ni2Mo, and duplex (austenitic and ferritic) in the case of 22Cr5Ni3Mo. Potentiodynamic experiments were employed to obtain electrochemical properties of investigated steels, followed by immersion tests to find ultimate conditions, where the steels still retain their passivity. After obtaining this information, scratch tests were performed to study the repassivation kinetics. It was found that repassivation times are similar for nearly all investigated steels independent of their chemical composition and microstructure.

scholarly journals Effect of heat treatment on the microstructure and corrosion properties of cast duplex stainless steels

2021 ◽  
Vol 225 ◽  
pp. 01003
Author(s):  
Aleksandr Fedorov ◽  
Andrey Zhitenev ◽  
Darya Strekalovskaya
Keyword(s):  
Heat Treatment ◽  
Experimental Study ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Stainless Steels ◽  
Formation Processes ◽  
Corrosion Properties ◽  
Quenching Temperature ◽  
Pitting Potential ◽  
Pitting Corrosion Resistance

The effect of the quenching temperature on the pitting corrosion resistance of lean duplex stainless steel (DSS) were examined. Using thermodynamic modeling of phase formation processes in steel during solidification and subsequent cooling was shown that the equal amount of austenite and ferrite is achieved at 1210°С for examined composition. Experimental steel samples were quenched from 1100 and 1200°С. It was found that as the temperature rises, the pitting potential increases significantly due to the achievement of a favorable phase ratio. The results of this experimental study made it possible to develop a heat treatment that provides high corrosion properties of lean DSS.

scholarly journals Influence of Vanadium and Cast Temperature on Nitrogen Solubility of Stainless Steel

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Saeed Ghali
Keyword(s):  
Stainless Steel ◽  
Chemical Composition ◽  
Stainless Steels ◽  
Induction Furnace ◽  
Nitrogen Solubility ◽  
Vanadium Content ◽  
Steel Grades ◽  
Cr 5.17 ◽  
Open Induction ◽  
Nitrogen Contents

Three stainless steel grades with different vanadium content were produced in open induction furnace. The base chemical composition of investigated stainless steel has contained 18.48–18.75% Cr, 5.17–5.62% Mn, 2.47–2.58% Mo, and 6.39–6.64% Ni. The vanadium contents of the three stainless steel grades were 0.009%, 0.112%, and 0.189%. The proposed stainless steels were casted at temperatures 1753 K and 1833 K. The nitrogen contents were determined for the produced steel grades at every cast temperature. The determined nitrogen contents were compared with those calculated from the developed equation of Grigorenko and Pomarin. The influence of cast temperature and vanadium content on nitrogen solubility was investigated. Interpretation between experimental and calculated nitrogen content was carried out. Increasing vanadium content and decreasing cast temperature were found to have positive significant effect on the nitrogen solubility. There were great deviations between experimental results and those calculated by Grigorenko and Pomarin equation.

NiAl precipitation in Fe-12w/o Cr-5w/o Ni-4w/o Al

1983 ◽  
Vol 41 ◽  
pp. 202-203
Author(s):  
L.E. Murr ◽  
J.S. Dunning ◽  
S. Shankar
Keyword(s):  
Solid Solution ◽  
Stainless Steel ◽  
Stainless Steels ◽  
Alloy Composition ◽  
Chromium Content ◽  
Scale Up ◽  
Optical Metallography ◽  
Property Evaluation ◽  
310 Stainless Steel ◽  
Microstructural Studies

Aluminum additions to conventional 18Cr-8Ni austenitic stainless steel compositions impart excellent resistance to high sulfur environments. However, problems are typically encountered with aluminum additions above about 1% due to embrittlement caused by aluminum in solid solution and the precipitation of NiAl. Consequently, little use has been made of aluminum alloy additions to stainless steels for use in sulfur or H2S environments in the chemical industry, energy conversion or generation, and mineral processing, for example.A research program at the Albany Research Center has concentrated on the development of a wrought alloy composition with as low a chromium content as possible, with the idea of developing a low-chromium substitute for 310 stainless steel (25Cr-20Ni) which is often used in high-sulfur environments. On the basis of workability and microstructural studies involving optical metallography on 100g button ingots soaked at 700°C and air-cooled, a low-alloy composition Fe-12Cr-5Ni-4Al (in wt %) was selected for scale up and property evaluation.

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