contribute to the volume fraction on nitrogen-enriched austenite with a higher pitting index value as indicated 
re deteriorate in weld metals by Ogawa and Koseki [2], and the enlarged precipitation area with increased 
hromium and ferrite content result in the degradation of the pitting corrosion resistance. In addition, the 
cipitation can formation of austenite platelets and chromium nitride, (Fig. 1f), during postsolidification cooling 
pitting. Using causes chromium-depleted regions in the ferrite and ferrite/austenite boundaries which are 
on the sulfide attacked preferentially, (Fig. 2), and lowered corrosion resistance too. The best resistance to 
2 fast anodic pit initiation of resolidified melt in the state after water quenching from high temperature 
and keeps the confirmed that the phenomena associated with solid state transformation predominantly control 
nite interface, the localized corrosion behavior of DSS alloys. 
V provokes 8 The examination of distribution of pits and their morphology have shown that these parameters 
ı of both main were very influenced by rapid cooling. Figure 4. shows the SEM micrographs obtained after the 
supposed that 
iated with the 
istent with the 
havior of cast 
» and at the 
tions of Pawel 
to pitting only EB 
ecause of the 
arlier that the 
1 increase its 
also that the 
ting in greater 
litrogen raises 
pe may Occur. i 
plained in this 
3a with highly 
rated in both, : . . . . ; 
; Fig. 4. SEM micrographs showing typical appearance of pitted surface of the 22.5Cr-8Ni- 
SE 2.5Mo-3Cu-0.1N DSS at different microstructural states: (a) as-cast base material, (b) 
: GTA resolidified and air cooled, (c), (d) GTA resolidified and water quenched. 
stable passive 
air cooled in potentiostatic tests. It was found that in the case of as-cast base material the total number of 
ie smaller and pits was smaller, but the average size was larger than in the case of GTA resolified melts. The 
ondary phases pits of the former are usually characterized by a deep and irregularly shaped hole. (Fig. 4a). In 
e decrease in contrast to this the pits formed in GTA resolidified melt are small, more regular and shallow. 
The higher amount of ferrite/austenite boundaries arranged on shorter distances provide more 
Prakt. Met. Sonderbd. 26 (1995) 305 
lo 
a 
© nN