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

• Published in: Materials characterization Vol. 86; pp. 69 - 79
• Main Authors: Fedrizzi, A., Pellizzari, M., Zadra, M., Marin, E.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.12.2013; Elsevier
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Mechanical alloying; Metal powders; Metals. Metallurgy; Microstructure; Phase diagram; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Powder metallurgy. Composite materials; Production techniques; Sintered metals and alloys. Pseudo alloys. Cermets; Solidification; Spark plasma sintering; Steel matrix composite; Spark plasma sintering; Microstructure; Phase diagram; Mechanical alloying; Steel matrix composite; Hot deformation; Plasma; Phase diagrams; Densification; Powder metallurgy; Spark discharge; Composite materials; Tool steels; Titanium boride; Sintering
• DOI: 10.1016/j.matchar.2013.09.012
• ISSN: 1044-5803

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® 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. •TiB2 reinforced steel matrix composites were produced by spark plasma sintering.•TiB2 was successfully dispersed in the steel matrix by mechanical alloying.•Steel and TiB2 react during sintering forming equilibrium Fe2B and TiC.•The new phases were investigated by means of AFM, Volta potential and XRD analyses.