Theromophysical Properties and Microstructure of Plasma-Sprayed Tungsten Coating on Low Activation Materials

Tungsten (W) coating on various low activation materials, such as ferritic steel (F82H), oxide dispersion strengthened (ODS) steel, and vanadium alloy NIFS-HEAT-2 (NH2) was successfully demonstrated by the vacuum plasma spray (VPS) process. Void and crack-type defects were observed in VPS-W. The mass density of VPS-W at room temperature (RT) was ∼90 % of the bulk W (sintered W). The thermal diffusivity and thermal conductivity of VPS-W from RT to 800 °C were 30∼50 % of the bulk W, while the linear expansion coefficient and specific heat of VPS-W were similar to the bulk W. The thermal conductivity of VPS-W was significantly lower than the bulk W, but was still larger than the NH2 substrate. There was no significant thermal contact resistance at the interface between W coating and NH2 substrate. Thus, the heat transfer properties of NH2 will not be degraded by the W coating with the VPS process.