Degradation processes such as wear, corrosion, cavitation, fretting and fatigue are active on the surface of the engineering component, and it follows that a suitably modified surface can be a powerful tool in improving the performance, and extending the service life, of engineering components.
Wear is damage to a solid surface involving the progressive mechanical loss of material due to the relative motion between two surfaces. Wear is commonly classified as sliding (typically referred to as adhesive, galling, metal-to-metal), abrasion or erosion wear
Refurbishment or reconditioning is the process whereby a damaged component is reclaimed to its original dimensions and functional state, typically through the localised application of a suitable coating. Often the functional performance (e.g. wear or corrosion resistance) can be significantly improved, e.g. a damaged seal landing on a shaft can be refurbished using a coating which is significantly more wear resistant than the original shaft material.
Repair and Refurbishment
Corrosion is damage to a metal surface involving electrochemical loss of material due to the oxidation of the metal. Corrosion is commonly classified as uniform, galvanic, crevice, pitting, intergranular, stress or erosion-corrosion. Corrosion can take place in the presence of liquids (aqueous, chemicals, molten metals and salts etc.), gases (air, atmospheres) and solids (soils).
Low-friction or slipperiness is a property of a surface whereby substances are prevented from sticking because the surface has been modified to provide a specific low coefficient of friction. This is usually achieved by coating the surface with a fluoropolymer material, often in combination with a thermal spray bondcoat. The thermal spray bondcoat provides improved adhesion and wear resistance to enhance the low-friction properties.
Traction is a surface property whereby substances are prevented from slipping because the surface texture has been modified to provide a specific high coefficient of friction. This is usually achieved by applying a thermal spray coating, often in combination with a polymer topcoat. The polymer topcoat makes it possible to provide traction with enhanced nonstick properties. High-friction coatings ensure tight starts, eliminate slippage, improve web tracking, improve tension control, and elimate wrinkles.
Anti-fouling is a property of a surface whereby the growth of marine organisms is prevented or suppressed because the surface has been modified to bio-toxic or non-stick. Non-toxic anti-sticking coatings prevent attachment of microorganisms thus negating the use of biocides. . This is usually achieved by coating the surface with a smooth hydrophobic thermal spray coating, often in combination with a polymer sealer.
Release (also called non-stick or cleanability) is a property of a surface whereby substances are prevented from sticking because of the hydrophobicity of the surface. This is usually achieved by coating the surface with special polymer materials, often in combination with a thermal spray bondcoat. The thermal spray bondcoat also provides a specific roughness profiles to the surface structure whereby the contact area is reduced and the nonstick properties enhanced.
Electrical insulation is a property of a surface whereby electrical current is prevented from flowing because the surface has been modified to be non-conducting. This is usually achieved by coating the surface with a ceramic material in combination with an insulating sealer.
Electrical Insulation/ Conduction
Heat transfer across a surface can be modified by the application of a suitable coating. Ceramic thermal barrier coatings reduce heat transfer, protecting the underlying material. Thermal conductivity can also be improved by the application of a suitable metallic coating.