High temperature creep study of recrystallized Tungsten: 3-point bending experiments and finite element simulation

In tokamak environment, plasma facing components made with tungsten as armor material will reach extreme temperature value up to 2000°C under stationary heat loadings. At such temperature, tungsten recrystallization and creep phenomenon become non negligible, this is why the particular creep behaviour of recrystallized ITER-grade tungsten is of interest. Previous study performed experiments on rods tungsten grades up to 1300°C and revealed that creep behavior of material is strongly dependent on chemical composition and manufacturing process. In order to fulfill the literature database, 3-points bending tests are performed from 1400°C to 1600°C on rolled tungsten, a potential candidate for future divertor. Experiments are achieved using thin rectangular samples of recrystallized tungsten. Tests are carried out at CEA Cadarache in a device usually used to study ceramics such as uranium dioxide. The purpose of these tests is, in-fine, to identify a creep material law for tungsten that may be used in fatigue analysis to describe the in-service behaviour of the component. In order to identify such a law which is dependent upon stress, strain rate, temperature and the material microstructure, constant crosshead speed experiments have been carried out under different conditions. Using a finite element model to describe the 3-point bending device, an attempt is made at modelling the creep behaviour of ITER-grade tungsten using a kinematic hardening law. Frederik-Armstrong law is used and numerical results obtained highlight that law parameters are well identified. In addition to the macroscopic bending tests, complementary SEM/EBSD examinations are carried out with the aim of identifying specific microstructural mechanisms based on the former works on uranium dioxide