Effect of deuterium on bonding quality of W/Ti/Steel HIP joints in first wall application.

Highlights • Ti is a potential low activation interlayer material to bond W/Steel for first wall application. • Microstructure and mechanical properties of W/Ti/Steel joints can be affected at lower deuterium concentration. • Ti interlayers crush into powder and W/Ti/Steel joints are failed at higher deuterium concentration. • Concentration of H isotope in W/Ti/Steel joints shall be strictly controlled for safety operation of fusion reactor. Abstract The first wall (FW) of a water cooled ceramic breeder (WCCB) blanket uses ferritic/martensitic steel (FMS) as structural material and tungsten (W) as armor material. The FW is exposed to fusion reaction fuels: deuterium (D) or tritium (T) plasma; and HT, T 2 , or HTO produced in breeding reactions. Titanium (Ti) is required as an interlayer in a W/FMS welding joint formed by hot isostatic pressing (HIP). However, Ti is sensitive to hydrogen (H) embrittlement which can result from the concentration and diffusion of H isotopes at welding interfaces. Qualitative analysis of the effect of D concentration on the W/Ti/FMS bonding quality was performed. The experiments demonstrated that D can affect the microstructure and mechanical properties of the W/Ti/FMS joints at lower D concentrations. Excessive TiD 2 will turn the Ti interlayer into powder, and finally lead to joint failure at higher D concentrations. The H isotope concentration in the joints shall be strictly controlled to ensure steady operation of the fusion reactor. [ABSTRACT FROM AUTHOR]