Microstructural Study Of Fusion Welds in 304L and 21Cr-6Ni-9Mn Stainless Steels (U) [report]

TOSTEN MICHAEL
2005 unpublished
Light-optical and transmission electron microscopy (TEM) have been employed to characterize the microstructures of a series of fusion welds made on 304L and 21-6-9 stainless steels. The materials investigated in this study included high-energy-rate-forged 304L, conventionally forged 21-6-9, and 304L weld critical plate (higher ferrite potential). The weld critical plate contained an electron beam weld (no filler wire) while other specimens were welded with various combinations of 308L, 309L
more » ... fied (MOD) and 312 MOD stainless steel filler wires to produce samples with a range of delta (δ) ferrite contents (4 to 33%) in the resulting welds. TEM specimens were prepared from broken arc-shaped, mechanical property test specimens that had been used to measure fracture toughness of the fusion welds. Specimens were prepared from regions of the weld heat-affected zones as well as from areas within the weld metal, including areas close to the fracture surface (plastically deformed regions). The observed microstructures varied according to the amount of δ ferrite in each weld. At the lowest ferrite levels the microstructure consisted of austenite and skeletal δ ferrite with austenite being the majority (matrix) phase. At intermediate levels of ferrite, lathy austenite/ferrite was observed and the ferrite became continuous throughout the specimens examined. In the weld with the most ferrite, many austenite morphologies were observed and ferrite was the matrix phase. Closest to the fracture surface an increase in dislocation density in both the ferrite and austenite were observed in all welds. Deformation twinning was also observed in the austenite. Many of the welds contained a large number of non-metallic inclusions (oxide particles) which most likely originated from impurities in the weld wires.
doi:10.2172/840795 fatcat:va45mkq6cvex3ma6agmzsaekgu