Research on the properties of bulk cementite prepared by mechanical alloying

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Cementite is one of the most important phases in steels, which plays a critical role in mechanical properties of steels. As a basic phase in steels, the understanding of its mechanical, physical and chemical properties is particularly desired. It is claimed to be metastable at all temperatures with respect to graphite and its saturated solution in iron.The present research has led to successful fabrication of bulk cementite by mechanical alloying (MA) with subsequent spark plasma sintering (SPS). Bulk cementite with dimensions of up to 50 mm in diameter have been produced. The mechanical and physical properties of Fe_3C have been measured.It was found that the color of cementite is metallic like pure iron. Its hardness is about 10GPa which is 10 times higher than that of pure iron. The Young's modulus of cementite is 190GPa and 10% smaller than that of pure iron. The electrical resistivity of cementite is 100/μΩ・cm and about 10 times higher than that of pure iron.The influence of Cr, Mn, V, Mo, Ti, Ni and Si additions substitutional to Fe on the structure and properties of cementite bulk has also been studied. It has been found that Cr, Mn, V and Mo can form alloyed cementite and stabilize it while Ti, Ni and Si destabilize or even suppress the formation of cementite. The hardness and Young's modulus of cementite were increased by the addition of both Cr and Mn. Thermal expansion coefficient was increased substantially by Cr or Mn additions. Slight decrease in Cp was observed by the addition of Cr or Mn.