Improvement of the oxidation resistance of spheroidal graphite cast irons with high silicon content through a new manufacturing process

High-silicon spheroidal graphite cast irons have a wide range of applications in various industrial sectors such as automotive, wind energy, and piping components. These cast irons present fully ferritic matrices, strengthened by solid solution hardening, and are characterised by several advantages compared to ferritic–pearlitic spheroidal graphite cast irons.

Some of these advantages include good oxidation resistance, improved machinability, and higher elongation under tensile loading for a given strength level.

In order to further improve the oxidation resistance of these materials, alloying additions such as aluminium, molybdenum, or nickel, as well as surface coating processes such as PVD or laser cladding, are commonly used. However, these approaches require complex procedures or the addition of high-cost elements, which increases the final product cost.

Therefore, this work proposes a new manufacturing process aimed at improving the oxidation resistance of these cast irons through the surface diffusion of selected elements such as nickel during the solidification process of iron castings.

The obtained results show that it is possible to form a nickel-enriched layer of 500–1000 µm through this process during solidification. This layer improves the oxidation resistance of spheroidal graphite cast irons when tested at 650 °C.