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1

Control of kinetics of plasma assisted nitriding process of Ni-base alloys by substrate roughness

Nowak Wojciech J.

Advances in Manufacturing Science and Technology

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2020

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Vol. 44, nr 3

99-108

EN

The present study investigated the effect of surface roughness on plasma assisted nitriding (PAN) process kinetics of Ni-base alloys. Two model alloys, namely Ni-10Cr and Ni-14Cr-4Al (wt.%) and commercial Rene 80, were examined. To elucidate the effect of surface roughness on nitriding kinetics, three methods of surface preparation were used, (1) polishing up with 1 μm diamond suspension, (2) grinding up to 220 grit sand-paper, and (3) grit blasting. The samples from each type of material were nitrided under the same conditions and investigated after processing. It was found that increase in roughness results in decreasing nitriding kinetics. The decrease of nitriding kinetics depends on alloy chemical composition, namely more complex chemistry resulted in smaller decrease of kinetics. Moreover, grit-blasting was found to be an improper method for surface preparation for PAN. The responsible mechanism for the effect of surface roughness on PAN kinetics of Ni-base alloys was proposed.

2

Plasma nitriding as a prevention method against hydrogen degradation of steel

Ćwiek J.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 36, nr 1

25-32

EN

Purpose: of this paper is evaluation of susceptibility to hydrogen degradation of structural low-alloy steel, plasma nitrided in the atmosphere with various contents of N2 and H2. Design/methodology/approach: Susceptibility of 34CrAlNi7-10 steel and samples with various plasma nitrided layers have been evaluated under monotonically increasing load in 0.005 M H2SO4 solution. The nitrided layers were investigated with the use of an X-ray Photoelectron Spectroscopy (XPS) and Auger Electrons Spectroscopy (AES). Slow-Strain Rate Tensile (SSRT) test was carried out under cathodic polarisation. Elongation, reduction in area, fracture energy and tensile strength were chosen as measures of susceptibility to hydrogen embrittlement. Fracture modes of failed samples were examined with the use of Scanning Electron Microscope (SEM). Findings: All tested samples revealed susceptibility to hydrogen degradation under hydrogenation. Samples with nitrided layer have lower lost of reduction in area than base metal samples. The nitrided layer established in standard atmosphere 30% H2 and 70% N2 has the highest resistance to hydrogen degradation. Research limitations/implications: Further research should be taken to reveal the exact mechanism of increased plasticity of nitrided layer with absorbed hydrogen. Practical implications: Plasma nitriding may prevent hydrogen charging of machines and vehicles parts in hydrogen generating environments, and thus decreasing susceptibility to hydrogen embrittlement. Originality/value: Under the increasing load and hydrogen generating environments plasma nitrided layers are effective barriers to hydrogen entry into a bulk of steel, and additionally increased plasticity of nitrided layers with absorbed hydrogen has been observed.

3

The use of nitriding as a prevention method against hydrogen degradation of high-strength steels

Błaszwiewicz M., Ćwiek J., Zieliński A.

Advances in Materials Science

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2007

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Vol. 7, nr 1(11)

107-112

EN

The paper presents evaluation of susceptibility to hydrogen degradation of high-strength low-alloy steel, plasma nitrided in the atmosphere with various contents of N2 and H2. Susceptibility of 34CrAlNi7-10 steel and samples with various plasma nitrided layers have been evaluated under monotonically increasing load in 0,005 M H2SO4 solution. Slow-strain rate tensile (SSRT) test was carried out under cathodic polarisation. Elongation, reduction in area, fracture energy were chosen as measures of susceptibility to hydrogen embrittlement. Fracture modes of failed samples were examined with the use of scanning electron microscope (SEM). Under the increasing load and hydrogen generating environments plasma nitrided layers are effective barriers to hydrogen entry into a hulk of steel, and additionally increased plasticity of nitrided layers with absorbed hydrogen bas been observed.

4

Effect of plasma nitrided layers on low-alloy steel on its hydrogen degradation

Zieliński A., Ćwiek J., Błaszkiewicz B.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

213--216

EN

Purpose: Purpose of this paper is evaluation of susceptibility to hydrogen degradation of structural low-alloy steel, plasma nitrided in the atmosphere with various contents of N2 and H2. Design/methodology/approach: Susceptibility of 34CrAlNi7-10 steel and samples with various plasma nitrided layers have been evaluated under monotonically increasing load in 0.005 M H2SO4 solution. Slow-strain rate tensile test (SSRT) test was carried out under cathodic polarisation. Elongation, reduction in area, fracture energy and tensile strength were chosen as measures of susceptibility to hydrogen embrittlement. Fracture modes of failed samples were examined with the use of scanning electron microscope (SEM). Findings: All tested samples revealed susceptibility to hydrogen degradation under hydrogenation. Samples with nitrided layer have lower lost of reduction in are than base metal samples. The nitrided layer established in standard atmosphere 30% H2 and 70% N2 has the highest resistance to hydrogen degradation. Research limitations/implications: Further research should be taken to reveal the exact mechanism of increased plasticity of nitided layer with absorbed hydrogen. Practical implications: Plasma nitriding may prevent hydrogen charging of machines and vehicles parts in hydrogen generating environments, and thus decreasing susceptibility to hydrogen embrittlement. Originality/value: Under the increasing load and hydrogen generating environments plasma nitrided layers are effective barriers to hydrogen entry into a bulk of steel, and additionally increased plasticity of nitrided layers with absorbed hydrogen was observed.

5

Hydrogen effects in the plasma nitrided galvanically deposited Cr layer.

Łunarska E., Nikiforow K., Wierzchoń T., Ulbin-Pokorska I.

Inżynieria Materiałowa

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2001

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R. XXII, nr 4

572-575

EN

The effects of plasma assisted nitriding of electrochemically deposited chromium layer on the hydrogen behavior were studied. The hydrogen content in Cr coating did not decreased during the plasma assisted treatment. Nitriding caused the formation of surface compact layer consisting of Cr2N+CrN nitrides and the nitride precipitates within the bulk of the Cr coating. The compact nitride layer and Cr2N precipitates serving as hydrogen traps prevented hydrogen to escape from Cr coating. At elevated temperature, hydrogen was observed to assist the chromium nitrides phase transformations.

PL

Badano wpływ jarzeniowego azotowania elektrochemicznie osadzonej warstwy chromu na zachowanie się wodoru. Zawartość wodoru w warstwie Cr nie obniżyła się wskutek obróbki jarzeniowej. Azotowanie spowodowało powstawanie powierzchniowej ścisłej warstwy, składającej się z azotków Cr2N+CrN, i wydzieleń azotków w objętości osadzonej warstwy Cr. Warstwa azotków i wydzielenia Cr2N, działają jako pułapki wodoru, zapobiegając jego wyjściu z pokrycia Cr. Stwierdzono wpływ wodoru na przemiany fazowe azotków chromu w podwyższonej temperaturze.