STABLE HIGH-TEMPERATURE π PHASE IN THE Fe-Mo-Cr-C SYSTEM: CRYSTALLINE STRUCTURE AND PROPERTIES

A bulk sample of composition 51.9Fe11.1Mo26.3Cr10.7C (at.%) with beta-Mn structure is prepared and examined by X-ray diffraction, high-temperature differential thermal analysis, and light microcopy. The stable high-temperature pi phase of beta-Mn type crystallizes congruently from the liquid phase in the Fe-Mo-Cr-C system, the singular point being found at about 51.9Fe11.1Mo26.3Cr10.7C at.% and 1520 +/- 25 K. The structural characteristics of the pi phase are presented. Its thermal expansion coefficient is 14.32 center dot 10(-6) K-1 and microhardness 15.9 GPa. The pi phase is characterized by high chemical resistance to inorganic acids and their mixtures from room temperature up to the boiling point.