CORROSION BEHAVIOR AND MICROSTRUCTURE IN 254-SMO-COMPARISON BETWEEN CONVENTIONAL AND P M HIP PRODUCTION/

Background/aims: In highly alloyed stainless steels, the precipitation of secondary phases may cause a deterioration of corrosion resistance . The powder method hot isostatic pressing (HIP) offers a means of min imising the segregation of alloying elements to central stringers. On the other hand, powder methods may give a higher content of oxide incl usions in the steel. The aim of this study was to compare the corrosio n properties of conventionally-produced and hot isostatically pressed 254SMO and relate corrosion resistance to microstructural changes duri ng sensitisation. Methods: Fitting corrosion resistance has been inves tigated by evaluating the critical pitting temperature in 1M NaCl and also investigating the sites for pit initiation. Electrolytic etching in oxalic acid has been used to assess susceptibility to intergranular corrosion. Microstructural changes has been studied in SEM, TEM and w ith powder X-ray diffraction. Results and conclusions: In terms of cor rosion resistance, there were no significant differences between the t wo materials, irrespective of heat treatment. Investigations in SEM of aged HIP material show a co-existence of a Mo-rich phase and a non-me tallic inclusion suggesting that nucleation of intermetallic precipita tes is facilitated by the presence of inclusions. (C) Munksgaard, 1997 .