Abstract
In this work, Grade 91 base metal was normalized with two different cooling conditions, water quenching and air cooling. The intercritical welding thermal cycle simulated by using the Gleeble system was applied to the heat-treated base metals to reproduce the intercritical heat-affected zone (ICHAZ). Microstructure, including precipitate and tempered martensite, of the base metal and ICHAZ was carefully characterized with advanced microscopy techniques. Creep strength of the simulated ICHAZs was evaluated at a high creep temperature of 650 °C with a stress of 100 MPa. A correlation between the microstructure and creep behavior of the ICHAZ is built to understand creep rupture mechanisms in the ICHAZ. The results show that more coarse carbides precipitated along the prior austenite grain boundaries after tempering in the water-quenched base metal. These carbides cannot be fully dissolved by the intercritical welding thermal cycle. The simulated ICHAZ generated from the water-quenched base metal underwent a higher grain recovery and growth during the typical post-weld heat treatment at 760 °C. Both simulated ICHAZs from two pre-weld heat treated base metals exhibit an extremely low creep resistance with a typical ductile fracture during creep testing. The faster grain growth and precipitate coarsening in the ICHAZ, simulated from the waterquenched base metal, made it even worse.
| Original language | English |
|---|---|
| Title of host publication | Materials and Fabrication |
| Publisher | American Society of Mechanical Engineers (ASME) |
| ISBN (Electronic) | 9780791858981 |
| DOIs | |
| State | Published - 2019 |
| Event | ASME 2019 Pressure Vessels and Piping Conference, PVP 2019 - San Antonio, United States Duration: Jul 14 2019 → Jul 19 2019 |
Publication series
| Name | American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP |
|---|---|
| Volume | 6B-2019 |
| ISSN (Print) | 0277-027X |
Conference
| Conference | ASME 2019 Pressure Vessels and Piping Conference, PVP 2019 |
|---|---|
| Country/Territory | United States |
| City | San Antonio |
| Period | 07/14/19 → 07/19/19 |
Funding
This work is funded by the Department of Energy R&D Award (FWP-FEAA118). R&D work is performed at the Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC for the U.S. Department of Energy under Contract DE-AC05-00OR22725. The authors would like to thank Mr. Doug Kyle for his assistance in creep testing experiments.