Development of Compound Layer of Iron (Carbo)Nitrides during Nitriding of Steel

Abstract

The composition and phase constitution of a compound layer developing during gaseous nitriding was investigated at 853 K for three commercial steels (AISI 120, 4340 and 1090) and Armco iron. The compound layers were characterised by light optical microscopy, X-ray diffraction and electron probe microanalysis. The formation of the compound layer occurs along two distinct sequences: α→γ′→ϵ and/or α ( θ)→ϵ 2 →γ′→ϵ 1 . The preferred sequence depends mainly on the chemical composition of steel and on the nitriding potential.