Czasopismo | RUDY I METALE NIEŻELAZNE | Rocznik 2014 - zeszyt 12

MICROSTRUCTURES AND MECHANICAL PROPERTIES OF A WARM PROCESSED SINTERED ULTRAHIGH CARBON STEEL

nr katalogowy: 88567

Fe-0.85Mo-0.6Si-1.4C ultrahigh carbon steel was liquid phase sintered to near-full density at 1300 °C, the temperature chosen as a result of generating a Thermo-Calc theoretical phase diagram. Major modifications in the mixing and sintering cycle steps of conventional powder metallurgy processing were required to attain near-full density. The sintered brittle microstructure comprised fine pearlite and grain boundary cementite networks. In order to obtain a strong, ductile spheroidised microstructure, several subsequent routes were investigated. The conventional heat treatment involved austenitisation, quenching and spheroidisation at 750 °C for 3 h, which resulted in a density of ~7.2 g cc-1, grain size of ~30 μm and a ferrite plus submicrometre carbide structure. Further densification and microstructural refinement were obtained by subsequent closed die forging. To discover whether the number of processing steps could be reduced, thermomechanical processing on Gleeble and Bähr machines was carried out on as-sintered and quenched specimens. Compression at 750 and 775 °C, to ~0.7 natural strain, of as-sintered material produced a banded structure of pearlite, ferrite and cementite, free of grain boundary carbides. Only processing at 700÷775 °C of either quenched or of already spheroidised specimens, however, resulted in full densification and spheroidised structures, finer in the case of the latter treatment. Hardness ranged from 765, quenched state, through 312, sintered, to 205÷289 HV10, spheroidised. Mechanical properties of the spheroidised specimens were: yield strengths up to 410 MPa, fracture strengths up to 950 MPa and strains up to 16 %. For a spheroidised and Gleeble 700 °C processed disc tested in diametral compression, the yield stress increased to 769 MPa and the transverse diametral extension was 23 %. Keywords: ultrahigh carbon steel (UHCS), liquid phase sintering, densification, forging MIKROSTRUKTURA I WŁASNOŚCI MECHAN[...]

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e-Publikacja (format pdf) - nr 88567 "MICROSTRUCTURES AND MECHA..." licencja: Osobista Produkt cyfrowy	10.00 zł

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RUDY I METALE NIEŻELAZNE - e-zeszyt (pdf) 2014-12 licencja: Osobista Produkt cyfrowy	32.00 zł

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2014-12

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