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

Abstract

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.

Active screen plasma surface co-alloying treatments of 316 stainless steel with nitrogen and silver for fuel cell bipolar plates

“…surface layers formed on the surface of the ASPA(N&Ag) samples are dense, almost featureless and uniform in thickness. According to the literatures [18][19][20][21], the formation of these thin surface layerscould be explained according to the principles of active-screen plasma treatment: materials are sputtered from the active screen and then deposit onto the surface during the treatment.The thickness of the top surface layers matches well with the high silver region measured by GDOES ( Figure 5(b)), indicating that the surface deposition layer is rich in silver.…”

Effect of Surface Deposits on Nitriding Layer Formation of Active Screen Plasma Nitriding

“…Several researchers have proposed a model of sputtering and deposition during ASPN. 10,13,19,20,35) In this model, nitrogen ions sputter the screen, the sputtered materials form nitrides with nitrogen in the plasma, and nitrides deposit on the sample s surface. It is thought that this model can be adapted to the bias-off of the ASPN process in this study.…”

“…[27][28][29][30][31][32][33][34] In a previous study, S phase was formed by ASPN. 9,16,17,33,35) A recent research suggested that a deposited layer was formed on the sample surface during ASPN. [36][37][38] However, little information has been reported on the effect of the surface deposits on the nitriding layer formation during ASPN process.…”

Controlling Nitrogen Dose Amount in Atmospheric-Pressure Plasma Jet Nitriding

“…Plasma nitriding is a surface technology to dope nitrogen atoms into metal surfaces via plasma chemical reactions to improve wear resistance, and fatigue strength, etc., of materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Plasma nitriding is now one of the essential surface treatments used in industry, especially in the automobile industry and die/mold fabrication.…”