Better environmental sustainability and reduced life-cycle costs are important drivers in industry today. Surface engineering is a valuable tool in achieving both of these by facilitating optimal materials selection and innovative product design.
Surface engineering spans a wide range of processes. At one end of the scale, ion implantation, nitriding and aluminising affect the chemistry and properties of only a thin surface layer of the substrate, by modifying the existing surface to a depth of 0.001–1.0mm. At the other end of the scale are weld hardfacings and other cladding processes. Typically 1–20mm thick, these are usually used for wear or corrosion resistance and repairing damaged parts.
Between these two extremes are deposition processes such as physical vapour deposition (PVD), chemical vapour deposition (CVD), anodising, laser processing, thermal spraying, cold spraying, and liquid deposition methods.
Coating application and performance characteristics are heavily dependent on composition and processing parameters. Coatings ranging from purely ceramic to purely organic in character have very different properties, but can provide critical benefits to the component.
Selection of the most appropriate coating type and deposition method requires an understanding of the operational requirements, together with the candidate application methods and supply chain considerations. Testing and validation of the surface is essential to ensure that the necessary fitness-for-purpose characteristics have been achieved, and comparison between candidate systems against established or developing standards has been undertaken.