Dissolved Nitrogen Concentration in Iron-Chromium Alloys by Plasma Nitriding

Abstract

  Fe-5, 10, and 14 mass%Cr alloy foils with the thickness of 60 μm or less were plasma nitrided at 873 K and nitrogen was saturated throughout the foil specimen.
   Microstructure on the cross section of the nitrided specimen was consisted of an external nitrided layer of γ′-Fe₄N and an internal nitrided layer of dispersed precipitates of CrN in the α-Fe matrix.
   Dissolved chromium was found to retain 1.23, 3.74, and 6.02 mass% by XPS (X-ray Photoelectron Spectroscopy) for the alloy specimens of Fe-5, 10, and 14 mass%Cr nitrided at 873 K for 180 ks, respectively. The results of XPS and the chemical analysis of total nitrogen lead to the conclusion that the concentrations of dissolved nitrogen were 0.41, 0.91, and 1.63 mass% in plasma-nitrided Fe-5, 10, and 14 mass%Cr alloy specimens, respectively. The dissolved nitrogen concentrations were significantly higher than those attained by gas nitriding.