BEYOND SURFACES

Technology & Innovation Turbine engine efficiency depends on thermal efficiency: the higher you can raise the temperature in the hot section of the engine, the better your fuel efficiency. That’s why turbine engine manufacturers want to turn up the heat in new engine designs. Thermally resistant coatings applied through thermal spray technology make it possible to turn up the heat to temperatures that, without these coatings, would melt turbine blades. But withstanding the higher tempera- tures being targeted for engines today requires coating materials of very fine powders — those with particle sizes 3 µm and lower, including submicron scale — to produce new, advanced coating microstructures. As such, cost-effective solution alternatives to traditional surface engineering processes used by aerospace engine manufacturers are needed to deposit more advanced thermally resistant coatings. “A coating structure made from much finer building blocks enables develop- ment of new coating structures with advanced functional properties,” says Applications Segment Manager Jim Girgulis. “You could develop coatings that are harder, more corrosion resistant, less permeable, or more strain tolerant. The capability also allows you to apply materials that have the right composition for their intended environment.” The catch is that these materials are too fine to be sprayed as dry powders. There are also health risks associated with the inhalation of these very fine powders, so special handling is necessary to protect against inadvertent inhalation. The answer is Suspension Plasma Spray (SPS), which is a new thermal spray process for producing coatings using these very fine powders. The key difference is that rather than feeding the coating material as a dry powder, these very fine particles are suspended in a liquid (usually an alco- hol). This is quite a challenge, as the suspension must be homogeneous and well-dispersed; in addition, it must achieve certain viscosity levels to meet feed consistency and spray quality requirements. Oerlikon is pioneering liquid suspension-based thermal spray technology that meets new application requirements and complies with health standards. Chris Dambra, Head of Coating Solutions Americas, says that Oerlikon offers customers “the ability to bundle the equipment, material and application to offer a package that’s tailored to their needs and attractive because of the unique microstruc- tures that can be created.” SPS technology has the potential for applications beyond turbine engines. SPS solutions are being tested and evaluated in aerospace, semiconductor, electronics and other industrial applications. “As node size goes down in semiconductors, coatings on equipment used to produce these chips need to have higher performance — defined by smoother coatings with less porosity,” Jim Girgulis says. “SPS technology allows us to make a leap forward in terms of producing smoother, denser, more erosion-resistant coatings with better dielectric prop- erties.” Further opportunities exist for applications in the manufacture of fuel cells, medical implants with coatings of biocompatible materials, and electrical elements in heaters, insulators and electric vehicles. Oerlikon Metco solutions cover the entire suspension spray process, from our new suspension feeder to hardware that converts spray guns to enable them to spray suspensions. We’re also expanding our portfolio of suspension and suspension-ready materials with excellent dispersion characteristics. Our team is available to launch programs for the custom development of new materials. For further information, contact your Oerlikon Metco account manager. Beyond SURFACeS 02|2020 29