Effect of potassium bubbles on the thermal shock fatigue behavior of large-volume potassium-doped tungsten alloy

Abstract

A newly developed large-volume potassium doped tungsten (W-K) plate with a thickness of 15 mm and a weight of 25 kg by powder metallurgy plus hot rolling was prepared to meet the requirements of International Thermonuclear Experimental Reactor (ITER) in engineering application. In order to clarify the effect of K doping on the thermal shock performance of W-K alloy, transient thermal shock tests with a single pulse duration of 1 ms for 100 shots at room temperature were performed. The absorbed power density is set to 0.33, 0.44, 0.55 and 0.66 GW/m2, respectively. Besides, the microstructure, Vickers micro-hardness before and after the transient thermal shock, thermal conductivity and relative density were also characterized. The results indicate that the cracking threshold of rolled W-K is 0.44-0.55 GW/m2, which possesses a better transient thermal shock resistance compared with the most of advanced W-based materials. This is mainly because that K doping can significantly improve the high-temperature stability and mechanical properties of W material without reducing its thermal conductivity. Especially, K bubbles can also effectively inhibit the formation and propagation of crack during thermal shock. Moreover, the cracking mechanism of rolled W-K alloy was also discussed in details. These studies are helpful to build a trusted ITER database on an advanced W-based materials, which provides useful references for the selection of future plasma facing materials.

Decreased surface blistering and deuterium retention in potassium-doped tungsten exposed to deuterium plasma following ion irradiation

“…For example, Tsuchida et al [58] reported that the KW has smaller grains than PW because K bubbles inhibit grain growth during manufacturing processes of W as well as recrystallization due to the pinning effect. Our previous publications also proved this, and the grain sizes of PW and KW can be found in [59,60], which are 9.82 and 2.81 µm, respectively. This means that KW has more grain boundaries that can provide more trapping sites for D, which thus facilitates the formation of surface blisters.…”