Alloying element nitride stability in iron-based alloys; denitriding of nitrided Fe–V alloys

Abstract

Recognising the various types of absorbed nitrogen in nitrided iron-based alloys and the lack of accuracy in local composition analysis of the individual nano-sized nitride precipitates (e.g. by atom probe tomography), precise determination of the nitride composition requires so-called denitriding treatments. This study proposes two routes to determine the nanonitride stoichiometry, which are demonstrated by experimental analysis of the denitriding behaviour in hydrogen gas of nitrided, model Fe-V alloys. The minimal nitrogen activity to stabilise the alloying element nitrides MeN in Fe-Me-N alloys is calculated. A strategy is offered to stabilise the alloying element nitrides and to determine the nitrogen content strongly bonded in the nitrides.

Plasma Nitriding of ISO 5832-1 Stainless Steel at 425 ºC with Intermittent Nitrogen Flow

“…When the flow is turned off, the chemical potential of the nitriding species drops to zero. As a consequence, the nitrogen close to the material surface is lost to the atmosphere 26 , while remaining nitrogen diffuses inwards. Hence, the nitrogen concentration in the layer decreases.…”

Improvement of stamping performance of H13 steel by compound-layer free plasma nitriding

“…Plasma nitriding is a kind of surface modification technology widely used for steels to improve their surface combined properties [9][10][11][12][13][14][15]. Generally, the nitriding layer formed during normal plasma nitriding is composed of compound layer and diffusion layer.…”

EFFECT OF NITROGEN HYDROGEN RATIO ON PLASMA NITRIDING FOR 38CrMoAl

“…Therefore, optimal combination of hardness, wear resistance and toughness are required for 38CrMoAl high-pressure valve. To meet the technical requirements, surface modification of high-pressure valves is necessary [3][4][5], and plasma nitriding is one of the most widely used surface modification techniques in industry, since a modified layer with high surface hardness and excellent wear resistance can be obtained [6][7][8][9]. Unfortunately, during conventional plasma nitriding, a hard and brittle compound layer (also called white layer) is generally produced, which is easy to crack and peel off from the surface during the service life of 38CrMoAl steel high-pressure valve upon subjecting the severe impact and cyclic load [10][11][12], and thus leading to premature failure of the components.…”