Cathodic cage plasma nitriding (CCPN) of austenitic stainless steel (AISI 316): Influence of the different ratios of the (N2/H2) on the nitrided layers properties

Freitas

et al. 2018

RBAV

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of the plasma nitriding conditions on the chemical and morphological characteristics of TiN coatings deposited on silicon

Freitas

et al. 2018

RBAV

“…[21][22][23][24] Several researchers have reported the effects of nitriding parameters such as the distance between screen and sample, screen size, gas pressure, gas composition, sample geometry, and bias voltage on ASPN properties. [25][26][27][28][29][30][31][32][33][34][35][36][37][38] However, little information has been reported on the effect of the screen's open area ratio on ASPN properties. In this study, ASPN has been performed on austenitic stainless steel by using three types of screens with various open area ratios to investigate the effect of the screen's open area on the nitriding properties.…”

Section: Introductionmentioning

confidence: 99%

Effect of Screen Open Area on Active Screen Plasma Nitriding of Austenitic Stainless Steel

2014

Austenitic stainless steel SUS 316L was nitrided by active screen plasma nitriding (ASPN) using screens with various open areas to investigate the effect of the screen's open area ratio on the nitriding response. The sample was placed on the sample stage in a floating potential and isolated from the cathodic screen and anode. The screen, which was SUS 316L expanded metal mesh with 38%, 48%, or 63% open area ratio, was mounted on the cathodic stage around the sample stage. Nitriding was performed in a nitrogen-hydrogen atmosphere with 25% N2 + 75% H2 for 18 ks at 693 K under 600 Pa by the ASPN process. After nitriding, the nitrided microstructure was examined using a scanning electron microscope and an electron probe microanalyzer. The phase structures on the nitrided surface were determined by X-ray diffraction. In addition, the surface hardness and cross section of the nitrided samples were measured by the use of a Vickers microhardness tester. The thickness of the nitrided layer of the S-phase decreased with increasing open area ratio of the screen.KEY WORDS: surface engineering; active screen plasma nitriding; cathodic cage; S-phase; stainless steel; open area ratio.

Section: Introductionmentioning

confidence: 99%

“…The methods of the second group include direct ion-plasma effect on the metal surface by a powerful short-pulse ion radiation or intense ion beams. They are applied, for example, in plasma-immersion ion implantation [3][4][5][6].The use of high-power compression plasma fl ows for the above-mentioned purposes opens new possibilities for modifi cation of the surface characteristics of various materials. The action of such fl ows on the metal surface makes it possible to form layers on this surface whose structural-phase composition has unique mechanical properties [7][8][9][10][11].…”

mentioning

confidence: 99%

Numerical Calculation of the Dynamics of Temperature Fields That Determine the Phase Composition of Polycrystalline Iron During Its Exposure to a Compression Plasma Flow

Astashinskii

2014

J Eng Phys Thermophy

The results of Stefan problem-based calculations of the distribution of nonstationary temperature fi elds in the surface layer of iron samples exposed to compression plasma fl ows at the given initial and boundary conditions are presented with account for the temperature dependence of the heat capacity and thermal conductivity of a sample. It is shown that on ultrafast heating and cooling (~10 7 K/s), an iron sample exhibits a modifi ed layer having a nonequilibrium microstructure and containing amorphous and nanocrystalline phases that increase its strength and wear resistance. Introduction.Of great interest at the present time is the search for new methods of processing materials, since the traditional chemicothermal technologies have practically been exhausted. The methods that are based on chemicothermal treatment of steels and that combine nitriding and the traditional high-temperature treatment have found widespread use. By their physical signifi cance such methods can be divided into two groups. The fi rst group comprises the methods of treating metal samples by concentrated energy fl uxes (for example, by laser radiation or electron beams) in a nitrogen atmosphere. Such methods envisage the maintaining of a rather high nitrogen pressure in the chamber during a long time of sample exposure to a series of pulses [1,2]. The methods of the second group include direct ion-plasma effect on the metal surface by a powerful short-pulse ion radiation or intense ion beams. They are applied, for example, in plasma-immersion ion implantation [3][4][5][6].The use of high-power compression plasma fl ows for the above-mentioned purposes opens new possibilities for modifi cation of the surface characteristics of various materials. The action of such fl ows on the metal surface makes it possible to form layers on this surface whose structural-phase composition has unique mechanical properties [7][8][9][10][11]. Such fl ows are produced in quasi-stationary plasma accelerators of the type of a magnetoplasma compressor [12]. It is shown in [8] that when a metal surface is exposed to the action of the indicated fl ows, high-temperature gradients appear within the metal that change its structure and phase composition.The effect of compression plasma fl ows on an iron sample leads to the formation in it of a polygonal cellular structure, a deep (to 60 μm) modifi ed surface layer based on nitrite phases, and then a zone of columnar grains spreading deeper into the bulk of the sample [9, 10]. The indicated layer consists of ferrite, martensite, austenite (C, N), and of the ε-nitride phase. The content of nitrogen in it attains 15-20 at.%. Such a surface structure is formed in the treated sample as a result of the eutectoid decomposition of its ε-region in cooling.One of the main factors that determine the structural-phase changes in the surface layer of a metal sample subjected to the effect of a compression plasma fl ow is the temperature fi eld distribution over the layer depth. The experimental determination of the dynamics of ...