Preparation, microstructure, and performance of ThO ₂ -doped tungsten alloy cathodes for high-power lamps

In response to the demand for tungsten (W) cathodes in high-power short-arc lamps, a powder metallurgy-swaging process was employed to fabricate thoriated W alloy rods with a diameter exceeding 30 mm. This approach successfully addressed issues related to the poor sintering performance and limited plastic deformation of large-diameter thoriated W rods. A comparative study was conducted on the microstructure and properties of thoriated W alloy with ThO ₂ doping (WT20) and W alloy co-doped with thorium oxide, potassium, aluminum, and silicon (WKT20). The co-doping strategy significantly reduced the grain size in both the sintered and swaged states of the W alloy, increased the proportion of small-angle grain boundaries, and ensured the uniform distribution of submicron-sized thorium oxide particles in the matrix. Consequently, the service life of W cathodes for short-arc lamps was markedly extended, with the WKT20 cathode maintained stable operation for 950 h and showed only limited shallow microcracks at the cathode tip, in sharp contrast to the severe cracking and spalling observed in WT20 after 50 h.