Stress Induced Nitrogen Diffusion in Nitrided Austenitic Stainless Steel

1970 ◽  
Vol 17 (1) ◽  
pp. 11-15 ◽  
Author(s):  
Teresa MOSKALIOVIENĖ ◽  
Arvaidas GALDIKAS
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Depth Profile ◽  
Nitrogen Concentration ◽  
Stress Gradient ◽  
Surface Concentration ◽  
Plasma Source ◽  
Fickian Diffusion ◽  
Internal Stresses ◽  
Nitrogen Diffusion

The nitrogen transport mechanism in plasma nitrided austenitic stainless steel at moderate temperatures (around 400 °C) is explained by non-Fickian diffusion model. The model considers the diffusion of nitrogen in presence of internal stresses gradient induced by penetrating nitrogen as the next driving force of diffusion after concentration gradient. For mathematical description of stress induced diffusion process the equation of barodiffusion is used, which involves concentration dependant barodiffusion coefficient. For calculation of stress gradient it is assumed that stress depth profile linearly relates with the nitrogen concentration depth profile. The calculated nitrogen depth profiles in an austenitic stainless steel are in good agreement with experimental nitrogen profiles. The diffusion coefficient D = 1.68-10 -12 cm2/s for nitrogen in a plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel at 380 °C was found from fitting of experimental data. It is shown that nitrogen penetration depth and nitrogen surface concentration increases with nitriding temperature nonlinearly.http://dx.doi.org/10.5755/j01.ms.17.1.241

scholarly journals Crystallographic Orientation Dependence of Nitrogen Mass Transport in Austenitic Stainless Steel

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 615 ◽  
Author(s):  
Teresa Moskalioviene ◽  
Arvaidas Galdikas
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Steel Surface ◽  
Hydrogen Plasma ◽  
Stress Gradient ◽  
Surface Concentration ◽  
Orientation Dependence ◽  
Surface Processes ◽  
Nitrogen Diffusion ◽  
Stress Induced Diffusion

The lattice stress-induced diffusion of nitrogen and hydrogen in austenitic stainless steel, taking place during nitriding in nitrogen/hydrogen plasma, is analyzed in the presented work. Stress-induced diffusion has an anisotropic nature and depends on the orientation of the crystal lattice. However, during simulations, it is not enough to take into account only the anisotropy of stress-induced diffusion, since this leads to contradictory results when comparing with experimental data. The problem is the surface concentration of nitrogen. Processes on the steel surface such as adsorption, desorption and heterogeneous chemical reactions are also very important. In the presented work, it is shown that these surface processes also have anisotropic natures, and it is very important to take this anisotropy into account during simulations. The influence of anisotropic surface processes on austenitic steel nitriding is analyzed in this study. It is shown that the nitrogen diffusion is anisotropic due to the effects of the anisotropic stress gradient and the anisotropic effects on the steel surface.

Effect of Pre-Shot Peening on Plasma Nitriding Kinetics of Austenitic Stainless Steel

2013 ◽  
Vol 634-638 ◽  
pp. 2955-2959 ◽  
Author(s):  
Lie Shen ◽  
Liang Wang ◽  
Jiu Jun Xu ◽  
Ying Chun Shan
Keyword(s):  
Stainless Steel ◽  
Surface Layer ◽  
Austenitic Stainless Steel ◽  
Shot Peening ◽  
Plasma Nitriding ◽  
Nitrogen Diffusion ◽  
X Ray Diffraction ◽  
304 Austenitic Stainless Steel ◽  
Strain Induced Martensite ◽  
Kinetics Of

The fine grains and strain-induced martensite were fabricated in the surface layer of AISI 304 austenitic stainless steel by shot peening treatment. The shot peening effects on the microstructure evolution and nitrogen diffusion kinetics in the plasma nitriding process were investigated by optical microscopy and X-ray diffraction. The results indicated that when nitriding treatments carried out at 450°C for times ranging from 0 to 36h, the strain-induced martensite transformed to supersaturated nitrogen solid solution (expanded austenite), and slip bands and grain boundaries induced by shot peening in the surface layer lowered the activation energy for nitrogen diffusion and evidently enhanced the nitriding efficiency of austenitic stainless steel.

scholarly journals Corrosion Properties of S-Phase/Cr2N Composite Coatings Deposited on Austenitic Stainless Steel

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 266
Author(s):  
Sebastian Fryska ◽  
Jolanta Baranowska
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Nitrogen Content ◽  
Polarization Resistance ◽  
Composite Coatings ◽  
Nitrogen Concentration ◽  
S Phase ◽  
Initial Surface ◽  
Corrosion Properties ◽  
Steel Substrates

In order to study the suitability of the S-phase layers as the interlayer for Cr2N chromium nitride coatings, a number of composite coatings were deposited by the reactive magnetron sputtering (RMS) method on austenitic steel substrates with various initial surface conditions (as delivered and polished) and their corrosion resistance was assessed. Coatings with S-phase interlayer were deposited at three different nitrogen contents in the working atmosphere (15%, 30%, and 50%), which influenced the nitrogen concentration in the S-phase. Coatings with chromium, as a traditional interlayer to improve adhesion, and uncoated austenitic stainless steel were used as reference materials. Detailed microstructural and phase composition studies of the coatings were carried out by means of scanning electron microscopy (SEM), optical microscopy (LM), and X-ray diffraction (XRD) and were discussed in the context of results of corrosion tests carried out with the use of the potentiodynamic polarization method conducted in a 3% aqueous solution of sodium chloride (NaCl). The performed tests showed that the electrochemical potential of the S-phase/Cr2N composite coatings is similar to that of Cr/Cr2N coatings. It was also observed that the increase in the nitrogen content in the S-phase interlayer causes an increase in the polarization resistance of the S-phase/Cr2N composite coating. Moreover, with a higher nitrogen content in the S-phase interlayer, the polarization resistance of the S-phase/Cr2N coating is higher than for the Cr/Cr2N reference coating. All the produced composite coatings showed better corrosion properties in relation to the uncoated austenitic stainless steel.

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