NITRIDING OF 2205 DUPLEX STAINLESS STEELS TO ENHANCE CORROSION RESISTANCE

Nitriding process had become favorable surface heat treatment in order to improve the
corrosion resistance by case hardening process on the material. The case hardening is
produced by diffusion of nitrogen and precipitation of the nitride layer on the surface of
material. Due to high alloying element, duplex stainless steel shows complex
precipitation behavior by forming different intermetallic phase which reduce corrosion
resistance in harsh environment such as high temperature in seawater, carbon dioxide
and hydrogen sulphide environment. Thus, high temperature gas nitriding process is
introduced. In this project, the high temperature gas nitriding process was conducted on
2205 duplex stainless steel at 1200°C for 8 hours and subjected to re-heating at
temperature of 700°C to prevent the effect of sensitization. The corrosion resistance is
analyzed by immersion test using weight loss method. The samples are subjected to
metallographic process to investigate the effect of microstructure after nitriding process
using optical microscopy (OM) and scanning electron microscopy (SEM). The
uniformity of nitrogen diffusion is identified by using energy dispersive spectroscopy
(EDS) on SEM.