High-resolution characterisation of chemically complex low alloyed high strength martensitic steels
| Reference number | |
| Coordinator | Swerim AB - Swerim AB, Kista |
| Funding from Vinnova | SEK 500 000 |
| Project duration | November 2018 - November 2019 |
| Status | Completed |
| Venture | Research infrastructure - utilisation and collaboration |
| Call | Research infrastructure - utilisation and collaboration: Industrial pilot projects for neutron and photon experiments at large scale research infrastructures - 2018 |
| End-of-project report | 2018-04413_SSAB.pdf (pdf, 191 kB) |
Purpose and goal
The purpose of the study was to evaluate low angle X-ray scattering method (ASAXS) to determine carbide types in complex microstructures, like annealing carbides in martensitic steels. The expereiments were made at Advanced Photon Source (APS), Argonne National Laboratory, USA. Material owner is SSAB Oxelösund, with interest to measure how small carbides, 1-10nm, change with time and temperature in order to optimize material selection and heat treatments. The ASAXS method was chosen to differentiate molybdenum-rich carbides from iron carbides, which otherwise produce similar scattering effects.
Expected results and effects
This study has shown that it is possible to distinguish small carbides within the same size range, using the ASAXS method. This is valuable information as there are often many carbide types in the same size range, especially for hardened and tempered martensitic steels. In the long term, it is expected that the used method offers valuable information to optimize the effects of molybdenum and vanadium in these steels. With better experimental information, the nucleation and growth processes can be optimised..
Planned approach and implementation
Participating parties, SSAB Oxelösund, KTH and Swerim, performed both in-situ and ex-situ experiments in the project. The ASAXS experiments were made with monochromatic light to measure energies close to 20 keV, in order to study the anomalous effect related to the presence of molybdenum for different particle sizes. The first data analysis shows that this effect occurs at high Q values and especially for long tempering times. This is expected, since molybdenum precipitate to small (1-10nm) secondary carbides.