High thermal shock resistance realized by Ti/TiH2 doped tungsten-potassium alloys

Abstract

Tungsten-potassium-titanium (W-K-Ti) alloys were fabricated by spark-plasma-sintering (SPS) and traditional rotary swaging (RS) techniques. Doping conditions and sintering methods were compared on the relative density, microstructure, hardness, recrystallization temperature, and the thermal shock resistance properties. Transient heat loads under 0.37 GW m−2 were applied on the W-K-Ti samples at room temperature for different cycles and pulsed durations. It was found that moderate Ti-doping (0.05 and 0.075 wt%) in W-K alloys can enhance the thermal shock resistance. Low-cycle thermal fatigue test suggested better thermal shock resistance in SPS-sintered W-K-Ti alloy (SPS-W-K-Ti) using TiH2 dopant. The main reason was that the decomposition of TiH2 significantly reduced the oxygen content of the ingots, which improved the ductility and thermal shock resistance of tungsten alloys. Further fracture analyses indicated that Ti-doping through TiH2 formed intra- and inter- Ti-rich voids in TiH2-doped W-K alloy, while only intergranular Ti particles were found lying along grain boundaries in the Ti-doped one. The formation mechanism of the Ti-rich voids was investigated in detail. This work provides a potential route for obtaining plasma facing materials with high thermal shock resistance.