2006 Volume 47 Issue 9 Pages 2302-2307
Compositions of type 304 austenitic stainless steels were modified with additions of boron, cerium and titanium. The additions of cerium and titanium removed free sulfur almost completely by formation of sulfides (Ce2O2S2 and Ti4C2S2), and led to precipitation of boron nitride onto creep cavity surfaces during creep exposure. Chemistries of the creep cavity surfaces, exposed by breaking creep exposed specimens at liquid nitrogen temperature under impact loading, were examined by Auger electron spectroscopy. The Auger spectra revealed the presence of boron nitride precipitating onto creep cavity surfaces. It was indicated that the boron nitride suppressed creep cavity growth and provided the steel with higher rupture strength and higher rupture ductility.