The Effect of the Nitrogen Absorption on the TEM Structure of SUS304L Austenitic Stainless Steel Weld Metal

The effect of the nitrogen absorption on the transmission electron microscopic structure of SUS304L austenitic stainless steel weld metal was investigated by varying the nitrogen partial pressure of the Ar-N2 gas mixture welding atmosphere in an atmosphere-controlling chamber. An electron diffraction study suggested that the primary solidification mode of the weld metal alters from ferritic mode to austenitic one with the nitrogen partial pressure and the nitrogen content of weld metal. The austenite frequently adopts a near Kurdjumov-Sachs orientation relationship with the adjacent primary ferrite, while the eutectic ferrite does not adopt the K-S one with the adjacent austenite. The amount of the eutectic ferrite phase increases with the nitrogen partial pressure and the nitrogen content. In the weld metal with no ferrite, precipitation on dislocations and grain boundaries was observed.