Structural and thermodynamic analysis of whiskers on the surface of grey cast iron

Abstract

The paper focuses, first, on the characterization of the whiskers on the surface of grey cast iron and second, it gives an explanation of whiskers growth based on thermodynamic calculations. The whiskers were observed on the surface of hot plates for the electric stove after black-oxide-coating (blackening) performed the furnace at 650°C in order to produce a protective layer mainly of magnetite (Fe3O4). However, the whiskers caused brown spots on dark grey surface and thus, the surface was aesthetically damaged. The investigations confirmed that whiskers are of hematite (Fe2O3); however, the thermodynamic calculations present that hematite may be formed as a result of the oxidation of magnetite if the partial pressure of oxygen is increased during the blackening.

Keywords

• whiskerswhiskers
• grey cast iron
• magnetite (Fe₃O₄)
• hematite (Fe₂O₃) grey cast iron
• magnetite (Fe₃O₄)
• hematite (Fe₂O₃)