HIGRAPH · Incorporation of solid lubricants into surface of friction parts engineered for high-temperature applications

Since traditional lubricants fail when friction is combined with high temperature, it is either impossible or impractical to use these materials in many industrial applications. The need for improved lubricating technologies is critical when trying to solve tribological problems concerning dry friction or boundary lubrication under high temperatures. The goal of the HIGRAPH project is to provide participating SMEs and the machinery industry with a novel technology for manufacturing sliding and rotating components that enhances dry-friction performance under high temperatures, increases durability, and extends the service lifetime of the part. It will be reached by encapsulation of High Temperature Solid-lubricant (HTSL) particles (such as WS2, WSe2, h-BN, Al-Mg-Si, BaF2, CaF2, etc.) into a micro-sized reservoirs. These reservoirs maintain the mechanical integrity of the matrix, and can slowly release the HTSL particles onto the sliding interface. As a result, both friction and wear are reduced. Friction forces and surface reactions generate a lubricious transfer film at the tribological contact, where a lubricating film with the required chemistry and structure is formed. This allows to retain the HTSL particles inside a hard, thermo- and oxidation-resistant matrix, and ensures operational integrity at extremely high temperatures. While maintaining low friction at high temperatures is important, wear resistance requires an additional blend of hardness and fracture toughness. Toughness of the developed coating will be enhanced through stress minimization, crack deflection, and ductility. The coating will be applied using powder metallurgy and sprayed coating modification methods to satisfy industrial requirements concerning coating thickness and allowable wear tolerance, which vary from 10–500μm.