Consideration of tungsten recrystallization in plasma facing components design

Tungsten recrystallization leads to a modification of material properties including a reduction in hardness, strength and thermal shock resistance. The recrystallization assisted material degradation compared to the asreceived state has made it very undesirable as demonstrated in high heat flux testing. Consequently, tungsten recrystallization temperature has been widely used as the upper limit of material surface temperature under steady state loading conditions. However, this study shows that recrystallization is inevitable where steady state or transient loads are high enough. The efforts to retard recrystallization will only reduce the recrystallized depth but cannot completely avoid it. While it is demonstrated the material will be weakened by recrystallization, the recrystallized depth plays a relatively small role in deciding the fatigue lifetime once it is recrystallized. Therefore, it is recommended that the geometry and fracture toughness of the design is optimised to reduce crack growth into the component. The design criterion against tungsten recrystallization under steady state loading conditions has also been proposed for engineering design stages.