Carbide induced embrittlement on tungsten wires

Abstract Heavily drawn and stress relieved non-sag tungsten wires are brittle at the ambient in torsion test in spite of their submicron sized fibre structure, when a part of their free surface is covered with tungsten carbide. The present study has shown that this kind of embrittlement may cease, if the stress relief anneal is performed at 1700 K for 15 min in an annealing atmosphere having an adjusted oxygen partial pressure of 10−4 mbar, while the samples remain brittle, when such annealing is carried out at an oxygen partial pressure of 10−6 mbar. Longer annealing periods at P(O2)=10−4 mbar exerts an adverse effect, as the strain at failure decreases gradually, when the annealing period is longer than 30 min at 1700 K. The oxygen induced decomposition of the carbide islands were monitored by means of their superconductivity. The carbon induced embrittlement upon stress relief of non-sag tungsten is also compared with the other types of embrittlement occurring in fibrous non-sag tungsten.