Microstructural Characterization of TiC-White Cast-Iron Composites Fabricated by In Situ Technique.

Aida B Moreira,Manuel F Vieira,Laura M M Ribeiro,Pedro Lacerda,Ricardo O Sousa,Ana M P Pinto

doi:10.3390/ma13010209

Abstract

High-chromium white cast-iron specimens locally reinforced with TiC–metal matrix composites were successfully produced via an in situ technique based on combustion synthesis. Powder mixtures of Ti, Al, and graphite were prepared and compressed to fabricate green powder compacts that were inserted into the mold cavity before the casting. The heat of the molten iron causes the ignition of the combustion reaction of the reactant powders, resulting in the formation of the TiC by self-propagating high-temperature synthesis. The microstructure of the resultant composites and the bonding interfaces was characterized by scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The microstructural results showed a good adhesion of the composite, suggesting an effective infiltration of the metal into the inserted compact, yet a non-homogeneous distribution of the TiC in the martensite matrix was observed. Based on the results, the in situ synthesis appears to be a great potential technique for industrial applications.

Highlights

High-chromium white cast irons are based on the iron–chromium–carbon system
The results of the granulometric distribution showed an average size of 43 μm and a D50 of 42 μm, meaning that 50% of the particles were less than 42 μm
High-chromium white cast-iron specimens locally reinforced with titanium carbide (TiC)–metal matrix composites were successfully produced via an in situ technique based on combustion synthesis, using powder mixtures of Ti, Al, and graphite

Summary

Introduction

High-chromium white cast irons are based on the iron–chromium–carbon system These alloys present an as-cast microstructure composed of a matrix of austenite (γ) or partially martensite (α’) with dispersed particles of iron–chromium carbides of M7 C3 type. During the following destabilization heat treatment, secondary precipitation of fine M23 C6 type carbides may occur together with the transformation of the γ into α’ [1,2,3,4]. The use of these alloys is widespread due to their high abrasive wear resistance. Alloys with a Cr level ranging from 12% to 30% are applied for crushers, rollers, ball mill liners, and pulverizing equipment, the type of equipment used in the mineral, mining, and cement industries [2,5,6,7,8].

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Conclusion