Application of technical nitrogen during gas nitriding austenitic steels

The possibility of using technical nitrogen including 0,2% O2 for activation austenitic steels surfaces during gas nitriding were investigated. By changing mole fraction of technical nitrogen i NH3 /N2t mixture one can regulate oxygen potential of gas atmosphere during heating the steel to nitriding temperature and sometimes during nitriding process. Four representative austenitic steels were nitrided with good results at 570°C and under 450°C. New method can be alternative to regulating oxygen potential by air and allows avoiding installing of firing mechanism and safety control.

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Corrigendum to “The thermoelectric sensor for controlling the gas nitriding process” [Sens. Actuators: A. Phys. 288 (2019) 144–148]

Sensors and Actuators A Physical ◽

10.1016/j.sna.2021.112635 ◽

2021 ◽

Vol 322 ◽

pp. 112635

Author(s):

Ireneusz Kocemba ◽

Jacek Rynkowski ◽

Walerian Arabczyk

Keyword(s):

Nitriding Process ◽

Gas Nitriding ◽

Thermoelectric Sensor

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Stacking Fault Energy in Relation to Hydrogen Environment Embrittlement of Metastable Austenitic Stainless CrNi-Steels

Metals ◽

10.3390/met11081170 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1170

Author(s):

Robert Fussik ◽

Gero Egels ◽

Werner Theisen ◽

Sebastian Weber

Keyword(s):

Phase Transformation ◽

Intermediate Stage ◽

Tensile Tests ◽

Stacking Fault ◽

Hydrogen Gas ◽

Stacking Fault Energy ◽

Austenitic Steels ◽

Aisi 304L ◽

Hydrogen Environment ◽

Gas Atmosphere

Metastable austenitic steels react to plastic deformation with a thermally and/or mechanically induced martensitic phase transformation. The martensitic transformation to α’-martensite can take place directly or indirectly via the intermediate stage of ε-martensite from the single-phase austenite. This effect is influenced by the stacking fault energy (SFE) of austenitic steels. An SFE < 20 mJ/m2 is known to promote indirect conversion, while an SFE > 20 mJ/m2 promotes the direct conversion of austenite into α’-martensite. This relationship has thus far not been considered in relation to the hydrogen environment embrittlement (HEE) of metastable austenitic CrNi steels. To gain new insights into HEE under consideration of the SFE and martensite formation of metastable CrNi steels, tensile tests were carried out in this study at room temperature in an air environment and in a hydrogen gas atmosphere with a pressure of p = 10 MPa. These tests were conducted on a conventionally produced alloy AISI 304L and a laboratory-scale modification of this alloy. In terms of metal physics, the steels under consideration differed in the value of the experimentally determined SFE. The SFE of the AISI 304L was 22.7 ± 0.8 mJ/m2 and the SFE of the 304 mod alloy was 18.7 ± 0.4 mJ/m2. The tensile specimens tested in air revealed a direct γàα’ conversion for AISI 304L and an indirect γàεàα’ conversion for 304mod. From the results it could be deduced that the indirect phase transformation is responsible for a significant increase in the content of deformation-induced α’-martensite due to a reduction of the SFE value below 20 mJ/m2 in hydrogen gas atmosphere.

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The influence of laser re-melting on microstructure and hardness of gas-nitrided steel

Archives of Mechanical Technology and Materials ◽

10.1515/amtm-2016-0004 ◽

2016 ◽

Vol 36 (1) ◽

pp. 18-22 ◽

Cited By ~ 2

Author(s):

Dominika Panfil ◽

Piotr Wach ◽

Michał Kulka ◽

Jerzy Michalski

Keyword(s):

Laser Beam ◽

Laser Treatment ◽

Diffusion Zone ◽

Nitrided Layer ◽

Nitriding Process ◽

Beam Power ◽

Gas Nitriding ◽

Nitrided Steel ◽

Laser Beam Power ◽

And Diffusion

Abstract In this paper, modification of nitrided layer by laser re-melting was presented. The nitriding process has many advantageous properties. Controlled gas nitriding was carried out on 42CrMo4 steel. As a consequence of this process, ε+γ’ compound zone and diffusion zone were produced at the surface. Next, the nitrided layer was laser remelted using TRUMPF TLF 2600 Turbo CO2 laser. Laser tracks were arranged as single tracks with the use of various laser beam powers (P), ranging from 0.39 to 1.04 kW. The effects of laser beam power on the microstructure, dimensions of laser tracks and hardness profiles were analyzed. Laser treatment caused the decomposition of continuous compound zone at the surface and an increase in hardness of previously nitrided layer because of the appearance of martensite in re-melted and heat-affected zones

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Gas Nitriding Process

Encyclopedia of Tribology ◽

10.1007/978-0-387-92897-5_100581 ◽

2013 ◽

pp. 1460-1460

Keyword(s):

Nitriding Process ◽

Gas Nitriding

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HAYNES NS-163 Alloy: A Novel Nitride Dispersion-Strengthened CO-Base Alloy

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4035625 ◽

2017 ◽

Vol 139 (7) ◽

Author(s):

Michael G. Fahrmann ◽

Vinay P. Deodeshmukh ◽

S. Krishna Srivastava

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Oxidation Resistance ◽

Base Alloy ◽

Nitriding Process ◽

Dispersion Strengthening ◽

Annealed Condition ◽

Gas Nitriding ◽

Diffusion Controlled ◽

Structural Applications

HAYNES® NS-163® alloy was developed by Haynes International Inc., Kokomo, IN, for high-temperature structural applications by pursuing a dual manufacturing approach: the fabrication of components in the readily weldable and formable mill-annealed condition, and their subsequent strengthening by means of a gas nitriding process. The latter process results in dispersion-strengthening by virtue of formation of internal nitrides. Since this process is diffusion-controlled, component section thicknesses are limited to approximately 2.0 mm (0.080 in.). Microstructures and mechanical properties of nitrided sheet samples are presented. Oxidation resistance and the need for coatings at temperatures exceeding 980 °C (1800 °F) are addressed as well.

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