Conclusions
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1.
A single strong discharge in an atmosphere of high-purity helium or air induces erosion of non-metallic inclusions in tungsten, which permits spectral analysis of the inclusion material extracted in the plasma and also facilitates observation of inclusions on microsections and microprobe analysis of them.
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2.
The most erosion resistant inclusions in tungsten are carbides and oxide inclusions such as SiO2 and Al2O3. Inclusions of more complex composition, containing silicon, aluminum, magnesium, calcium, barium, and potassium together are eroded more easily. Metallic impurities (titanium, iron, zirconium, and others) are found in the solid solution or in negligible quantities in high-melting impurities. Along with carbides and oxides, there are some inclusions with hydrogen and nitrogen, probably of the type of carbonitrides, oxynitrides, or oxyhydrides.
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Literature cited
E. M. Savitskii and G. S. Burkhanov, Metal Science of Alloys of Refractory and Rare Metals [in Russian], Nauka, Moscow (1971), p. 157.
E. M. Savitskii et al., "Metallography of cast tungsten," Izv. Akad. Nauk SSSR, Metally, 6, 177 (1972).
S. A. Skotnikov, "Determination of nitrogen in metals," in: Transactions of Institute of Metallurgy [in Russian], No. 115, Izd. AN SSSR, Moscow (1963), p. 43.
Additional information
A. A. Baikov Institute of Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 42–45, November, 1974.