Solution heat treatment of plasma nitrided 15-5PH stainless steel - Part I: Improvement of the corrosion resistance

Abstract

The results of the investigation on Solution Heat Treatment of Plasma Nitrided (SHTPN) precipitation-hardened steel 15-5 PH are presented. The layers have been obtained by the plasma nitriding process followed by solution heat treatment at different temperatures. The influence of the solution heat treatment after nitriding on the dissolution process of the nitrided layer has been considered. The nitrided layers were studied by scanning electron microscopy, X-ray microanalysis (EDX), and X-ray diffraction. Micro-hardness tests of the nitrided layers and solubilized nitrided layers have been carried out and interpreted by considering the processing conditions. It was found that high nitrogen austenitic cases could be obtained after SHTPN of martensitic precipitation-hardened steel (15-5PH). When Solution Heat Treatment (SHT) was performed at 1100• C, some precipitates were observed. The amount of precipitates significantly reduced when the temperature increased. The EDX microanalysis indicated that the precipitate might be chromium niobium nitride. When the precipitation on the austenite phase occurred in small amount, the corrosion resistance increased in SHTPN specimens and the pit nucleation potential also increased. The best corrosion result occurred for SHT at 1200

Nitrogen Surface Enrichment of Austenitic Stainless Steel ISO 5832-1: SHTPN vs Low-temperature Plasma Nitriding

“…Several techniques are being used to improve the surface characteristics of these steels, like plasma nitriding at low temperatures [1][2][3][4] , ion implantation 5 , and high temperature gas nitriding (HTGN) 6 . More recently, the so-called "Solution Heat Treatment after Plasma Nitriding" (SHTPN) process was proposed as a new method for surface enrichment of nitrogen in solid solution, with good results regarding improvement of corrosion resistance of stainless steels 7,8 . Plasma nitriding at relatively high temperatures (723 K or more) increases the surface hardness with consequent higher wear resistance of these steels; however, it can lead to the formation of CrN phases.…”

“…Hence, the use of plasma nitriding is limited to the low temperature range, where only the formation of the S-phase (also called expanded austenite -γ N ) occurs 1,12,13 . The S-phase formation on austenitic stainless steels by advanced nitriding treatments has been the subject of several studies [1][2][3][4][5][6][7][8][9][10][11][12][13] . Theo focus of this work is not the study of the S-phase itself, rather the SHTPN process as an alternative to low temperature plasma nitriding.…”

Obtenção de austenita expandida (fase S): Nitretação por plasma em baixa temperatura x SHTPN - Parte 2

“…Este fato, aliado a baixa dureza e propriedades tribológicas, limita sua aplicabilidade. Várias técnicas vêm sendo empregadas com o objetivo de melhorar as características superficiais destes aços por meio da adição de nitrogênio em solução sólida [1][2][3][4][5][6][7].…”

“…Este fato, aliado a baixa dureza e propriedades tribológicas, limita sua aplicabilidade. Várias técnicas vêm sendo empregadas com o objetivo de melhorar as características superficiais destes aços por meio da adição de nitrogênio em solução sólida [1][2][3][4][5][6][7].A adição de nitrogênio aos aços inoxidáveis austeniticos traz melhoras expressivas em propriedades tais como a resistência a corrosão por pite, corrosão sob tensão e fadiga [8].Nos aços inoxidáveis austeniticos o nitrogênio melhora a resistência à corrosão intergranular, pois retarda a precipitação de fases intermetálicas, além do que, a precipitação de nitretos traz uma perda menor no teor de cromo da matriz que na precipitação de carbonetos [8]. A resistência à corrosão localizada e ainda Autor Responsável: Ricardo Fernando dos Reis Data de envio:…”

Nitrogen enrichment of AISI 409 stainless steel by solution heat treatment after plasma nitriding

“…Solid solution nitrogen-enriched surfaces can also be achieved by Solution Heat Treatment after Plasma Nitriding (SHTPN). This process consists of the regular surface by nitriding, followed by a diffusion treatment at a material-specific temperature [9][10][11].…”