Lifetimes and Failure Mechanisms of W/Re Hairpin Filaments

仪器资料 · 发表于 2018-6-11 13:55:23

Lifetimes and Failure Mechanisms of W/Re Hairpin Filaments
A life test of tungsten hairpin filaments used in a high-reliability electron beam instrument has
been carded out to improve knowledge of filament life and failure mechanisms as a function
of temperature. These filaments are made of nonsag tungsten/3 pct rhenium (W/3 pct Re) wire.
A steep reduction in filament life is observed at 2760 K, which is not predicted by models
which assume thermal evaporation as the principal failure mechanism. Failure analysis of the
filaments shows that the sudden loss of life at 2760 K is the result of localized hot-spot formation
caused by the accumulation of voids at grain boundaries. Examination of the crystal growth and
growth rates indicates that the recrystallization temperature, TRee, occurs near 2760 K for the
nonsag W/3 pct Re wire used in these filaments. This suggests that void accumulation acts as
the principal, life-limiting failure mechanism; spontaneous recrystallization at 2760 K increases
the rate of void growth and causes a severe reduction of filament life.

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