No abstract

For engineering materials such as cast aluminum or cast iron used in wear applications, the wear surfaces are modified to increase wear resistance. Conversion coatings are the most common surface modification methods in many alloys in which the wear surfaces are chemically, electrochemically or thermally activated and converted into coherent ceramic structures that are resistant to wear. The development of conversion coatings is controlled by the diffusion mechanisms of the functional film 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 structures to the diffusion behaviors of the conversion coating forming elements and the general coating characteristics. Processes to produce desirable substrate microstructure in order to achieve preferred coating characteristics at lower processing costs and methods to measure the effective functional film thickness are proposed.