Microstructural evolution in high temperature nitrogen implanted stainless steel

Using cross-sectional transmission electron microscopy (XTEM), a sandwich of layers was observed on the surface of 316 stainless steel, implanted with high dose of nitrogen ions at 350 degrees C, by plasma immersion ion implantation. The sandwich comprised a nanocrystalline outer layer about 1 mu m thick (I), a 0.6 mu m thick amorphous layer (II) and a 0.4 mu m thick semi-amorphous layer (III) above the substrate. The evolution of this sandwich of layers is discussed based on the results of nano-beam diffraction (NBD) and high resolution transmission electron microscopy (HREM). It is proposed that nitrogen concentration plays a key role in determining the microstructure of the implantation modified substrate.