Modeling of Stress and Temperature Effects on Creep of Reduced Activation Ferritic-Martensitic Steel Alloy F82H (Tertiary Creep Modeling of RAFM Steel)

Technical Report · Sat Mar 01 04:00:00 EST 2025

DOI:https://doi.org/10.2172/2573321· OSTI ID:2573321

Aduloju, Sunday C. ^[1]; Frizt, John ^[2]; Huang, Chaofan ^[3]; Joseph, Roshan ^[3]; Messner, Mark ^[4]; Truster, Timothy J. ^[5]

---

1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
2. Univ. of Tennessee, Knoxville, TN (United States)
3. Georgia Inst. of Technology, Atlanta, GA (United States). Georgia Tech Research Institute
4. Argonne National Laboratory (ANL), Argonne, IL (United States)
5. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)

A Bayesian optimization procedure is presented for calibrating a multi-mechanism micromechanical model for creep to experimental data of F82H steel. Reduced activation ferritic martensitic (RAFM) steels based on are the most promising candidates for some fusion reactor structures. Although there are indications that RAFM steel could be viable for fusion applications at temperatures up to 600 °C, the maximum operating temperature will be determined by the creep properties of the structural material and the breeder material compatibility with the structural material. Due to the relative paucity of available creep data on F82H steel compared to other alloys such as Grade 91 steel, micromechanical models are sought for simulating creep based on relevant deformation mechanisms. As a point of departure, this work recalibrates a model form that was previously proposed for Grade 91 steel to match creep curves for F82H steel. Due to the large number of parameters (9) and cost of the nonlinear simulations, an automated approach for tuning the parameters is pursued using a recently developed Bayesian optimization for functional output (BOFO) framework [1]. Incorporating extensions such as batch sequencing and weighted experimental load cases into BOFO, a reasonably small error between experimental and simulated creep curves at two load levels is achieved in a reasonable number of iterations. Validation with an additional creep curve provides confidence in the fitted parameters obtained from the automated calibration procedure to describe the creep behavior of F82H steel at 600 °C. The model is further extended using a temperature dependent scaling law approach to simulate creep response between 550 °C and 650 °C. The efficacy of this extension is compared with the previously used scaling law approach for Grade 91 steel.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE; National Science Foundation (NSF)
• DOE Contract Number: AC05-00OR22725; AC02-06CH11357
• OSTI ID: 2573321
• Report Number(s): ORNL/TM--2025/3780
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE