Role of Ion-Beam Processing Time in the Formation and Growth of the High-Nitrogen Phase in Austenitic Stainless Steel

Published

November 1, 2000

Author(s)

D L. Williamson, P J. Wilber, F R. Fickett, S Parascandola

Abstract

A systematic series of AISI-316 stainless steel samples has been prepared as a function of exposure time to a nitrogen ion beam Times from 15 to 4 h were selected with other conditions maintained as follows: sample temperature + 410 C, accelerating potential = 700 V, beam current density + 2.0 mA/cm², Compositional, structural, magnetic, and diffusion properties were studied with a combination of x-ray diffraction, backscatter Mossbauer spectroscopy, magnetic force microscopy, surface profilometry, and glow-discharge optical emission spectroscopy. The only N-containing phase detected for all processing times was the high-N-solid solution phase, γ_N and its maximum N content was found to grow rapidly to a saturation value exceeding 30 at % A carbon contamination layer, in the form of a C solid solution phase γ_c, was detected below the γ_N and was found to be introduced during the Ar-ion sputter-cleaning/heating step used prior to exposure to the N-ion beam. This C-rich layer is punished ahead of the incoming N. The γ_N layer thickness growth can be modeled with a simple diffusion-plus-sputtering depth for the given processing conditions. The surface roughness increases with processing time. Anisotropy in the lattice expansion for different lattice planes parallel to tge sample surface and varying magnetic properties in the different surface grains are observed. This is likely due to a mixture of residual stress and N-composition variation effects. Ferromagnetic maze-like domain structures are observed on the 1 micron size scale.

Proceedings Title

International Current Status Seminar on Thermochemical Surface Engineering of Stainless Steels; Stainless Steel 2000 | | | Manley Publications for the Institute of Materials in Association

Conference Dates

November 1, 2000

Conference Location

Osaka, 1, JA

Conference Title

International Current Status Seminar on Thermochemical Surface Engineering of Stainless Steels

Pub Type

Conferences

Keywords

austenite, ion implantation, magnetics, MFM, stainless steel, surface modification

Citation

Williamson, D. , Wilber, P. , Fickett, F. and Parascandola, S. (2000), Role of Ion-Beam Processing Time in the Formation and Growth of the High-Nitrogen Phase in Austenitic Stainless Steel, International Current Status Seminar on Thermochemical Surface Engineering of Stainless Steels; Stainless Steel 2000 | | | Manley Publications for the Institute of Materials in Association, Osaka, 1, JA (Accessed March 14, 2025)