Microstructural evaluation of molybdenum-containing stainless steel weld metals by a potentiostatic etching technique

Microstructure of austenitic stainless steel weld metals is complicated by the presence of delta-ferrite and microsegregated regions rich in chromium and molybdenum, as well as other minor alloying elements such as sulphur an d phosphorus at the delta/gamma interphase boundaries. Detailed microstruct ural studies are required in order to establish correlation between various metallurgical as well as electrochemical corrosion properties with the wel d metal microstructure. The conventional chemical etching technique was fou nd to be inadequate in revealing different microconstituents. A powerful po tentiostatic etching technique was used to reveal not only ferrite but also different microconstituents that had different specific electrochemical po tentials at which they dissolved. This paper describes the weld metal micro structure developed by the addition of molybdenum (4.16-5.83 wt%) to type 3 16 stainless steel weld metals during Tungsten Inert Gas (TIG) welding with different heat inputs. (C) 1998 Chapman & Hall.