Surface modification of ductile iron produced by an innovative in-situ casting technique

In this study, a chromium carbide layer was fabricated by an in-situ casting technique on ductile iron cast components. The procedure consists of (i) applying a ferrochrome slurry at the surfaces of silica sand moulds to create a surface layer (e.g. coating) and (ii) use a ductile iron alloy to cast the coated moulds. The microstructure of the realised surface layer was characterised and analysed via Scanning Electron Microscopy (SEM), optical microscopy (OM) and X-ray Diffraction (XRD).The corrosion behaviour of the samples was analysed by an electrochemical method using 0.03 M NaCl. The wear tests and Vickers hardness measurements were performed to determine the properties of the surface layer. It was determined that the layer is composed of chromium carbide (Cr7C3), ledeburite and pearlite. The ‘chromium carbide’constituent improved significantly both the wear resistance and the hardness of the surface layer. Electrochemical measurements have indicated that the carbide-based layer exhibits a lower corrosion resistance than the substrate (e.g. casting).