Incandescent lamp

摘要

An improved incandescent lamp filament is described having an inner core of doped tungsten crystals with a surface layer of chemically vapor deposited undoped tungsten crystals. The inner core material exhibits the sag-resistant grain structure obtained with dispersion alloy products of tungsten whereas the unalloyed tungsten crystals in the surface layer are of a finer size and can further exhibit a preferred crystallographic orientation. Incandescent lamps utilizing said improved tungsten filaments exhibit increased vibration resistance and greater notch resistance when operated on direct current.