タングステン合金焼結材の高温強度特性

抄録

Thoriated tungsten alloy (ThO₂-W) has been used as cathode material in discharge lamp and for TIG welding rod because of its excellent thermoelectric emission properties. However, ThO₂ is one of radioactive substances, therefore development of thoria free tungsten is desired. In this study, hafnium carbide (HfC) was used as an alternate material of ThO₂. The material used, HfC-W alloys was produced with spark plasma sintering (SPS) and tensile strength of the alloy at elevated temperature was evaluated. Tensile strength of HfC-W sintered by SPS decreased with increasing testing temperature. Tensile strengths at 1300 and 1500°C in HfC-W sintered by SPS were lower that in the same alloy but sintered by conventional electrical sintering technique. According to microstructure observation by SEM-EDS in the materials used, coarse aggregate of HfC were observed in HfC-W sintered by SPS, while small HfC particles were distributed in the matrix for HfC-W sintered by electrical sintering. It is considered that difference in dispersion state of HfC particles possibly affects tensile strength of the materials used.