Colours take a shine to coated steels

It is now possible to lay down coloured, wear resistant coatings on steel strip which enhance both performance and appearance and open up a wide range of applications. Overall strip thicknesses range from foil thicknesses to several mm thick with coating thicknesses from nanometres to microns, single or multi-layered, and if necessary, different on the two sides of the strip. Peter Gossas, president of Sandvik Materials Technology refused to be drawn when asked about the technologies used to manufacture the new coatings, and said that no outsiders were allowed to visit the factory used to make them. He nonetheless let slip the fact that coatings could be made incorporating titanium carbo nitride. This strongly suggests that they are deposited by physical vapour deposition and related methods under near vacuum conditions, which would explain both their appearance, and the wide range of possibilities and combinations available to customers. In appearance, those shown to Eureka had a similar finish to typical anodised aluminium coatings, except they were on steel. They can incorporate any metallic element, including aluminium, nickel, copper and silver or compounds such as aluminium oxide or titanium oxide. The company has a particular skill with applying such coatings at low cost. At the same event, Terry Allison managing director of Dormer tools, mentioned the fact that one of the challenges his business had faced was producing a new range of drills with titanium nitride coated tips that could be sold for around 70p each, despite the fact that the cost of producing the coating had previously been about £1 per drill. Applications are still being developed with customers, and "Some 50 trial deliveries have been made". Most were not identified, but one that could be described was using the technology to make switch domes for mobile phone keypads, cameras and other electrical consumer durables out of thin steel strip coated with nickel or silver. The strip can be cold formed and bent to tight radii. Cutting, stamping, grinding and deep drawing present no problem. Peter Gossas said that laser welding could be undertaken at, "Extremely low welding powers", but this did produce a local effect on the surface finish. Base materials offered are: austenitic, martensitic, ferritic and duplex stainless steels as well as precipitation hardenable steels, nickel based alloys, and low alloy and carbon steels. The strip can be supplied in coils, bundles, on spools or in cut lengths from 0.4 to 4m. Sandvik Materials Technology email Peter Rose, UK managing director Pointers * Steel substrates are from foil thicknesses to a few mm thick * Coatings can incorporate any element and some compounds * Coating thicknesses are from nanometres to a few microns. * Coatings can be single or multi-layer, and can be different on the two sides of the strip