Microstructural study and densification analysis of hot work tool steel matrix composites reinforced with TiB₂ particles

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• 作者：A. Fedrizzi ; M. Pellizzari ; M. Zadra ; E. Marin
• 关键词：Steel matrix composite ; Spark plasma sintering ; Mechanical alloying ; Microstructure ; Phase diagram
• 刊名：Materials Characterization
• 出版年：December, 2013
• 年：2013
• 卷：86
• 期：Complete
• 页码：69-79
• 全文大小：3009 K

文摘

Hot work tool steels are characterized by good toughness and high hot hardness but are less wear resistant than other tooling materials, such as high speed steel. Metal matrix composites show improved tribological behavior, but not much work has been done in the field of hot work tool steels. In this paper TiB₂-reinforced hot work tool steel matrix composites were produced by spark plasma sintering (SPS). Mechanical alloying (MA) was proposed as a suited process to improve the composite microstructure. Density measurements and microstructure confirmed that MA promotes sintering and produces a fine and homogeneous dispersion of reinforcing particles. X-ray diffraction patterns of the sintered composites highlighted the formation of equilibrium Fe₂B and TiC, as predicted by thermodynamic calculations using Thermo-Calc庐 software. Scanning electron microscopy as well as scanning Kelvin probe force microscopy highlighted the reaction of the steel matrix with TiB₂ particles, showing the formation of a reaction layer at the TiB₂-steel interface. Phase investigations pointed out that TiB₂ is not chemically stable in steel matrix because of the presence of carbon even during short time SPS.