Hardening of gray irons in surface chilling with a low-temperature plasma
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By plasma surface fusion in gray irons with lamellar and spheroidal graphite it is possible to obtain a hardened case with a hardness of not less than 580–600 HV and a structure characterized by high inhomogeneity, which consistas basically of quasiledeburite, cementite, carbides, martensite, residual austenite, bainite, sorbite, and graphite in various ratios and quantities depending upon the form of the iron and the treatment conditions.
The best quality of hardened layer is observed in irons with spheroidal and lamellar graphite with a carbon equivalent of 3.5–3.7 with a case thickness of not more than 1.2–1.5 mm, a preheat temperature of 400°C, and a ratio of vp/tp=(10–20)·10−6 cm/(sec·deg).
KeywordsGraphite Carbide Austenite Martensite Cementite
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