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

摘要

Ni thin films of 250 nm thicknesses were coated on type 304 and 316 stainless steels and post NT 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_2 SO_4 solution was investigated by means of potentiodynamic technique. Nano-structure and crystallography of the films showed the development of Ni_3N(l11) and Ni_4 N(200) 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 μAcm~(-2) (for SS(316)) and 0.56 μAcm~(-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.