Joining of 14YWT and F82H by Friction Stir Welding

Conference · Mon Dec 31 23:00:00 EST 2012

OSTI ID:1104787

Hoelzer, David T ^[1]; Unocic, Kinga A ^[1]; Sokolov, Mikhail A ^[1]; Feng, Zhili ^[1]

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1. ORNL

The feasibility of using friction stir welding (FSW) to join specimens of the advanced oxide dispersion strengthened (ODS) 14YWT nanostructured ferritic alloy (NFA) and a plate of F82H tempered martensitic steel (TMS) was investigated. The sample used in the FSW experiment consisted of spot welding four specimens 14YWT prepared from prior tested dual notch fracture toughness bend bars in a corresponding slot that was machined in the F82H plate. The FSW run was successfully performed on the sample using a polycrystalline boron nitride tool (PCBN) that resulted in joints showing good bonding between butt joints of 14YWT specimens and 14YWT specimens and F82H plate. The joints were characterized by light microscopy and SEM analysis and were observed to be relatively narrow in width. The ultra-fine grain size associated with 14YWT increased by a factor of up to 3 while that of F82H was refined by a considerable amount in the thermomechanically affected zones (TMAZ) due to FSW. In addition, porosity was observed in the TMAZ of 14YWT on the advancing side of the FSW joint and at the interface between F82H and 14YWT. Vickers hardness (VH) measurements showed a decrease of ~120 VH from ~500 VH (~20% decrease) for 14YWT and an increase of ~220 VH from ~220 VH (~100% increase) for F82H in the FSW zones. Further refinements in the FSW process will be required to minimize defects including porosity.

• Research Organization: Oak Ridge National Laboratory (ORNL); Shared Research Equipment Collaborative Research Center
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1104787
• Country of Publication: United States
• Language: English