100 years of doped tungsten wire

TLDR: In this article, the development of the PM processing steps and tools used by William D. Coolidge in 1909 marks the breakthrough for the usage of tungsten filaments in the lighting industry and the beginning of the industrial era of modern powder Metallurgy.

Abstract: From a historical point of view, the development of the PM processing steps and tools “for making tungsten ductile” by William D. Coolidge in 1909 marks the breakthrough for the usage of tungsten filaments in the lighting industry and the beginning of the industrial era of modern Powder Metallurgy. Some important technological developments before introducing the Coolidge process will be described briefly (Just and Hanaman procedures, Kuzel process, Pintsch method) together with the corresponding implications for today's modern technologies and materials (Sol-Gel, CVD, MIM, ODS alloys, W-RE welding electrodes). With regard to the Coolidge process some always recurring misunderstandings, especially of the doping process, will be corrected. In addition, some accompanying discoveries and inventions (Tungsten Heavy Metals, Gradient Materials, Cemented Carbides) will be mentioned too. Finally, the scientific importance of the potassium bubbles as the strongest pinning points at highest temperatures against the movement of dislocations and grain boundaries will be highlighted shortly. Considering geometrical dimensions, the microstructural features of the finest wires and the corresponding fabrication of diamond dies, necessary for the deformation of wires, also represent precursors of today's nanotechnology and micromachining.