Abstract
Carbides existing at equilibrium with austenite in molybdenum steels were studied by electrolytic isolation and by subsequent chemical and X-ray analyses. Three kinds of carbides, M3C, ξ and M6C, were found in the steels quenched from 900°C. Besides these carbides, M2C appeared in the case of short time austenitizing. By addition of Cr (about 1%) to molybdenum steels, M23C6 was stabilized, and this carbide was also found in the quenched structures. On the bases of these experimental results, the stable and the metastable carbide phase diagrams at 900°C were determined. It was confirmed that MaCb found by Kuo (1953) in several tempered molybdenum steels was identical with ξ carbide, which had been first noticed by Takei (1932). The X-ray photograph of ξ carbide resembles to that of Hägg’s iron percarbide, and so the crystal structure of ξ carbide is probably the orthorhombic.
