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A comparative study was performed on the microstructures and the mechanical properties of STD11and 8Cr steel. The specimens were quenched from 1030 o C and tempered at 240C and 520C. Vickers hard-ness, impact toughness and tensile tests were conducted at various tempering temperatures. Microstructuralcharacterization to measure grain size, volume fraction of retained austenite and distribution of carbides was car-ried out by using SEM, EBSD, TEM and X-ray diffraction techniques. Due to finer M 7 C 3 carbides dispersed, 8Crsteel showed larger impact toughness and plasticity than STD11 irrespective of the tempering temperature. While8Cr steel had lower hardness in as-quenched state and after tempering at 240 o C owing to smaller carbide con-tent and more retained austenite, it was harder after tempering at 520 o C due to larger precipitation hardeningfrom finer M 23 C 6 .(Received August 25, 2014; Revised September 12, 2014; Accepted September 18, 2014)Key words : Cold-work tool steel, 8Cr steel, STD11, Microstructure, Mechanical property |
