Plasma ferritic nitrocarburising of carbon and low alloy 0·4%c steels in N₂–H₂ atmospheres with CO₂ gas additions

Abstract

Plasma ferritic nitrocarburising of carbon and low alloy 0·4%C steels was carried out at 570°C in a N2–H2 atmosphere containing CO2 gas additions. The influence of the atmosphere composition, the duration of treatment, and the composition and microstructure of the steels on the phase composition of the compound layer was investigated. The formation of a monophase ɛ compound layer was not possible with the parameters used in this study. The phase composition of the compound layer was found to be very dependent on the amount of CO2 in the process gas. A difference in the plasma nitrocarburising behaviour of the two low alloy steel grades was observed, and the formation of some austenite in the diffusion zone of one of the steels, at the interface with the compound layer, is proposed to explain this observation.

Spectroscopic investigations of plasma nitrocarburizing processes using an active screen made of carbon in a model reactor

“…Assisted by pulsed dc discharges, plasma nitriding and plasma nitrocarburizing have been employed as surface engineering methods to improve the tribological properties of metal surfaces for several decades. In a variety of applications, the traditional conventional plasma nitriding technique (CPN) has become an industrial standard approach for surface hardening and surface modification [1][2][3][4][5]. These methods are based on thermochemical diffusion processes.…”

Tool steel ion beam assisted nitrocarburization

“…Different approaches have been proposed and studied to produce better surface properties with nitrogen and carbon inclusion via plasma techniques, including pulsed plasma, r.f. plasma, and plasma immersion ion implantation [7][8][9][10][11]. These studies used plasmas composed of nitrogen gas (sometimes diluted in hydrogen gas) and, for carbon carrying gas, carbon dioxide, or some hydrocarbon gas such as methane or acetylene.…”

“…However, they present restrictions related to handling and environmental problems due to the use of explosive or toxic materials [6]. The plasma nitrocarburizing prevents some of these problems but, unlike from gas or salt bath, have not been reported to produce a monophase  compound layer [7]. Different approaches have been proposed and studied to produce better surface properties with nitrogen and carbon inclusion via plasma techniques, including pulsed plasma, r.f.…”

Tratamentos de superfícies de uma liga ferrosa por íons de nitrogênio

“…O gás e o sal são bem estabelecidos para aplicações industriais, mas implicam em alguns inconvenientes relacionados ao uso de materiais explosivos ou tóxicos [20]. A nitretação a plasma evita alguns desses problemas, mas, em contraste com as outras, apresenta maiores dificuldades na formação de uma monofase ε-Fe 3 (N,C) [21]. Diferentes abordagens foram propostas e estudadas para produzir melhores propriedades superficiais, incluindo plasma pulsado, plasma de rádio-freqüência e implantação iônica por imersão em plasma [21,22,23,24,25,26] [27,28].…”

“…A nitretação a plasma evita alguns desses problemas, mas, em contraste com as outras, apresenta maiores dificuldades na formação de uma monofase ε-Fe 3 (N,C) [21]. Diferentes abordagens foram propostas e estudadas para produzir melhores propriedades superficiais, incluindo plasma pulsado, plasma de rádio-freqüência e implantação iônica por imersão em plasma [21,22,23,24,25,26] [27,28]. Mesmo que importante em alguns sistemas para a incorporação de nitrogênio, o hidrogênio pode alterar, de maneira ainda não esclarecida, o processo de nitretação no volume.…”