On the kinetics of nitride and diffusion layer growth in niobium plasma nitriding

Kertscher, Ricardo; Brunatto, Sílvio Francisco

doi:10.1016/j.surfcoat.2020.126220

Cited by 8 publications

(3 citation statements)

References 35 publications

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“…10. The diffusion coefficient D was determined by the following approximation: 32,33) where d is the depth of the nitrided layer and t is the treatment time. The diffusion coefficients of the samples nitrided under a V Fe of − 50 or + 3 V (experimental conditions without sputtering) were constant.…”

Section: Resultsmentioning

confidence: 99%

Effect of Sputtered Fe on the Plasma Nitriding Mechanism of AISI H13 Tool Steel Using Electron-Beam-Excited Plasma

2021

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Section: Resultsmentioning

confidence: 99%

Effect of Sputtered Fe on the Plasma Nitriding Mechanism of AISI H13 Tool Steel Using Electron-Beam-Excited Plasma

2021

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“…Heat transfer mechanisms and cleaning of the particle surfaces in the plasma environment are suggested to be responsible for the enhanced sintering. Despite the plasma reactivity may be prejudicial to sintering if the plasma atmosphere reacts with the ceramic or composite substrate material, as discussed in [6], the plasma reactivity can be advantageous for the metallic materials processing as observed from nitriding [7][8][9][10][11] and carburizing [12,13] treatments, which can be simultaneously carried out during the plasma sintering of powder materials as in linear glow discharge as in hollow cathode discharge [14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Surface state change influence’s theoretical approach of pressed iron on hollow cathode discharge characteristics: first results of plasma heating reproducibility for sintering purposes

Brunatto¹

2022

Surf. Topogr.: Metrol. Prop.

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In this work first results of the plasma heating process reproducibility for sintering purposes of pressed iron powder sample was investigated analyzing changes on the current-voltage characteristics of pulsed direct current (dc) Ar + H2 hollow cathode discharges sequentially carried out. For this purpose, the temperature of a sample acting as central cathode was varied by changing the switched-on time (duty cycle) of the pulse, via plasma species bombardment (ions and fast neutrals), which typically occurs in both cathode cylindrical surfaces that constitute the annular (hollow cathode) glow discharge, and measured by a thermocouple inserted in the central cathode sample holder. After two sequential plasma heating experiments, the third one practically reproduced the measured plasma parameters evidenced in the second heating, and the respective heating curves as a function of the time have led to similar current-voltage characteristics suggesting the iron sample sintering in non-isothermal way. Principles comprising plasma-surface interface and metallurgical-physical-chemical reactions, powder surface aspects, thermodynamic properties, metallurgical transformation of the pressed sample, and hollow cathode discharge properties are presented and discussed. The main points considered in the present approach are related to plasma (oxygen-affected plasma ionization, high ionization and excitation rate, and the intense light radiation of the annular glow discharge), thermodynamics (oxidation-reduction reactions, electron work function, sintering driving force, and surface energy), and powder (particle size distribution, morphology, specific surface, and iron recrystallization). To the best of the author's knowledge, it is the first time that it is brought to the light the changes on hollow cathode discharge characteristics while an iron sample acting as the central cathode of an annular glow discharge is subjected to distinct heating steps on the temperature range of 20 to ~1250 °C, leading it to have its sintering initiated.

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“…Concerning the influence of the processing parameters studied here, the literature is rich for austenitic stainless steels (ASSs) plasma nitriding [19][20][21][22][23][24][25][26][27][28][29] , but very poor for MSSs, being mainly focused on treated surface characteristics of different materials, through different processes [30][31][32][33][34][35][36][37][38][39][40] . It is to be noted that almost nothing has been published aiming to study such effects on the MSSs LTPC.…”

Section: Introductionmentioning

confidence: 99%

Effects of the Voltage and Pressure on the Carburizing of Martensitic Stainless Steel in Pulsed DC Glow Discharge

et al. 2021

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In the present work, the influence of the pulse voltage and pressure on the treatment glow discharge characteristics and consequently on the surface properties obtained for low temperature plasma carburized AISI 420 martensitic stainless steel was investigated. Two distinct sets of samples were carburized at 450 °C, for 8 h, one aiming to study the applied pulse voltage effects, which was varied for 500, 600 and 700 V, at a fixed pressure of 400 Pa, and the other aiming to study the pressure effects, which was varied for 200, 400, and 800 Pa, at a fixed pulse voltage of 700 V. Treated samples were characterized by means of confocal laser scanning microscopy (CLSM), X-ray diffraction (XRD) analysis, microhardness and roughness measurements. The glow discharge (plasma) was characterized by optical emission spectroscopy (OES) and current measurements. Results show that the edge effect, surface roughness, hardness and outer layer growth kinetics are dependent on the studied plasma parameters. OES analyses showed that the pulse voltage parameter does not promote significant changes on the plasma chemistry, but confirmed that the molecular H 2 gas dissociation rate tends to be significantly affected by the pressure parameter giving important support for the results obtained here.

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On the kinetics of nitride and diffusion layer growth in niobium plasma nitriding

Cited by 8 publications

References 35 publications

Effect of Sputtered Fe on the Plasma Nitriding Mechanism of AISI H13 Tool Steel Using Electron-Beam-Excited Plasma

Effect of Sputtered Fe on the Plasma Nitriding Mechanism of AISI H13 Tool Steel Using Electron-Beam-Excited Plasma

Surface state change influence’s theoretical approach of pressed iron on hollow cathode discharge characteristics: first results of plasma heating reproducibility for sintering purposes

Effects of the Voltage and Pressure on the Carburizing of Martensitic Stainless Steel in Pulsed DC Glow Discharge

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