Effect of hydrogen and oxygen on stainless steel nitriding

Abstract

Articles you may be interested inPlasma nitriding process by direct current glow discharge at low temperature increasing the thermal diffusivity of AISI 304 stainless steel J. Appl. Phys. 113, 063507 (2013); 10.1063/1.4790631Flux effect on the ion-beam nitriding of austenitic stainless-steel AISI 304LNitrogen and oxygen transport and reactions during plasma nitridation of zirconium thin films Nitriding stainless steels at moderate temperature: Time-and depth-resolved characterization of the near surface composition during the nitriding processThe influence of hydrogen and oxygen on stainless steel implanted by nitrogen low-energy ions is systematically studied. It is shown that hydrogen intervenes moderately in the process only when the oxygen partial pressure in the deposition chamber is relatively high. For very low-oxygen partial pressures, the energetic nitrogen molecules impinging on the substrate sputter the thin oxide layer formed on the substrate. This allows the growing of a rich nitrogen layer beneath the surface, improving the diffusing of the implanted atom deeper in the bulk material. For higher-oxygen partial pressures, the sputtering is ineffective, and an oxide layer partially covers the surface even in the presence of hydrogen. The maximum depth penetration of nitrogen depends on the degree of oxygen coverage, which is fairly well described by a Langmuir absorption isothermal. Hardness depth profiling is consistent with the existence of a diffusion barrier formed by the oxygen absorbed on the surface. In order to understand the role of hydrogen on the nitriding process, samples preimplanted with hydrogen were subsequently treated with nitrogen and the hardness depth profiling analyzed. These results may provide a clue about the practical consequences of oxygen and hydrogen on the nitriding process.

Previous heat treatment inducing different plasma nitriding behaviors in martensitic stainless steels

“…[6][7][8][9] In order to improve the nitrogen chemical potential for further nitrogen diffusion, plasma immersion ion implantation ͑PI 3 ͒ becomes a suitable technique because the high voltage applied produces an energetic ion bombardment, thus augmenting the nitrogen retention. [10][11][12][13] Furthermore, plasma nitriding of austenitic stainless steels is a model system where PI 3 demonstrated the efficiency of decreasing the surface potential barrier compared to rf plasma.…”

Structural and mechanical properties of radiofrequency N2/H2cold plasma-nitrided C38 carbon steel

“…Indeed, the use of hydrogen in a ~25 vol. % presents a combined role, first it increases the thickness of surface nitride layer (combined layer) by reducing the oxide layer [14,[24][25][26] and secondly during the plasma treatment hydrogen increases the density of active nitriding species [15]. However, the increase of hydrogen content (~75 vol.…”

“…However, an experimental evidence shows that the active nitriding species are not ionic [10][11][12][13], and it is now well-known that nitriding can occur without the presence of hydrogen. The role of hydrogen was generally attributed to the enhancement of the nitrogen atom diffusion by removal of the surface oxides by a chemical mechanism, resulting in a thicker nitride-layer [14]. But a high concentration of hydrogen slows the nitriding process, resulting in a thinner nitrided layer [15].…”

Nitrogen diffusion enhancement in a ferrous alloy by deuterium isotopic effect

“…8,9 The presence of oxygen can limit the available nitrogen on the surface for diffusion into bulk material because of both energetic and geometric effects. Thermodynamically, metal-oxygen bonds are more stable than metal-nitrogen bonds, promoting the formation of metallic oxides instead of metallic nitrides when oxygen is adsorbed.…”