Influence of Ni deposition and subsequent N + ion implantation at different substrate temperatures on nano-structure and corrosion behaviour of type 316 and 304 stainless steels

Abstract

Ni thin films of 250 nm thicknesses were coated on type 304 and 316 stainless steels and post N + ion implanted at 15 keV energy with a fluence of 5 × 10 17 N + cm −2 at different substrate temperatures. Surface nano-structure of the samples were analysed using X-ray diffraction (XRD), atomic force microscopy (AFM) before corrosion test and scanning electron microscopy (SEM) after corrosion test. Corrosion behaviour of the samples in 1.0 M H 2SO 4 solution was investigated by means of potentiodynamic technique. Nano-structure and crystallography of the films showed the development of Ni 3N(1 1 1) and Ni 4N(2 0 0) orientations with a minimum surface roughness and grain size at 400 K substrate temperature. The highest corrosion resistance with a corrosion current of 0.01 μA cm −2 (for SS(316)) and 0.56 μA cm −2 (for SS(304)) was achieved in case of samples which were N + ion implanted at 400 K. Results for both types of stainless steels showed good agreement and the better performance of SS(316) was attributed to the 2% molybdenum contents in the alloy composition of this type of stainless steel, which enhances the effectiveness of nitrogen in retarding the corrosion process.