Influence of the Metal/Mold Processes on the Casting Mechanical Parameters and Corrosion Resistance

Abstract

This chapter presents the issue related to the morphology of graphite, namely, flake/compacted/spheroidal graphite that is the main controlling factor of the mechanical and physical properties of cast irons. It is presented that flake graphite in the surface layer can be regarded as a local source of stress concentration and thus the crack growth resistance of the cast iron with flake graphite is extremely poor. It has also been shown that the presence of flake graphite in the surface layer has a significant influence on the mechanical properties of spheroidal graphite cast iron (SGI) and compacted graphite cast iron (CGI), including firstly its plasticity, which decreases with the increasing thickness of the flake graphite layer. Moreover it was shown that the presence of flake graphite makes the surface layer brittle, non-plastic, which results in forming cracks. No flake graphite in the surface layer causes the specimen to deform uniformly, providing the most favorable combination of mechanical properties. Finally, the results of SGI iron corrosion resistance, performed in 0.1 M sodium chloride solution, are shown. It has been indicated that the presence of a thick layer of flake graphite in the surface layer of the castings significantly increases the cathode current, which stimulates the cathodic reaction and oxygen reduction.