The effects of secondary phase to the diffusion-induced surface treatment

For soft engineering materials such as aluminum and cast iron used in wear applications, the wear surfaces are modified for such purposes. Conversion coating is the most common surface modification method in many alloys where the wear surfaces are chemically, electrochemically or thermally activated and converted into coherent ceramic structures (usually in microscopic scale) that are resistant to wear. The development of conversion coatings is controlled by the diffusion behavior of the ceramic forming elements and affected by many factors such as temperature, chemistry and microstructure of the substrate. This paper attempts to examine the effects of the secondary phases in the cast structure to the diffusion behavior of the conversion coating forming species and the general coating characteristics. Processes to produce the desired substrate microstructure to achieve required coating characteristics at lower processing costs are proposed.