INFLUENCE OF SIGMA PHASE ON GENERAL CORROSION OF AUSTENITIC STAINLESS STEEL

Abstract

Austenitic stainless steel is mostly used at high temperatures. It is known that during heating of the austenitic stainless steel with increasing temperature and time of annealing a microstructure is changed i.e. there is the precipitation of carbides followed by precipitation of secondary phases as a sigma phase. The presence of the delta ferrite in austenitic stainless steel enhances the formation of the sigma phase. This study represents the influence of delta ferrite on the sigma phase formation and the effect of the sigma phase on general corrosion. Corrosion tests were conducted in the corrosion cell according to Standard ASTM G5, on instrument potentiostat/galvanostat, Princeton Applied Research, model 263A-2, with the software PowerCORR® (Standard, ASTM G5-94). Examinations were carried out in 1% HCl and 10% FeCl3 solutions. Tafel extrapolation method was used for the investigation of general corrosion. The results of corrosion testing indicated that the intensity of the general corrosion increases with the increase of the delta ferrite and sigma phase contents.

Keywords

• austenitic stainless steel
• general corrosion
• delta ferrite
• carbides
• sigma phase