Hard alloys

The continuing technological development in many fields of industry, such as machine, equipment, and plant construction, marine technology, as well as environmental technology, has resulted in stringent demands for new materials. Besides high wear resistance, these materials must also exhibit high corrosion resistance and good thermal properties. In many industries, machine and tool components become severely worn during operation. As a result, the operating efficiency and the quality of the product are impaired, and equipment failure may be the final consequence. Wear and tear of this kind cause severe losses, and predictions indicate that these costs will continue to increase in the future. With the combination of abrasive wear, thermal stresses, and possibly corrosive attack, the demands imposed on the surface material of the components become more stringent. For protecting these functional surfaces, which are subject to combined wear, weld surfacing is applied to an increasing extent for reasons of cost and efficiency. In correspondence with the requirements, multiphase cladding materials are employed for the purpose, as specified in DIN 8555. These materials include especially hard alloys on an iron, nickel, and cobalt basis. Furthermore, intermetallic alloys and mixed powders are employed; these products consist of a ductile matrix alloy and highly wear-resistant hard material particles. With the use of these materials, the hardening behaviour and the associated properties and stability of the protective cladding can be appropriately adjusted to resist wear and corrosion, among other factors. For the components to be clad, the correct choice of welding filler implies finding the correct compromise between maximal wear resistance, corrosion resistance, and economically acceptable machining costs, since the wear-resistant claddings thus applied must be machined because of the required surface quality and dimensional tolerances.

The high-temperature materials include all products which can be employed on components for sustained service above 500 °C and which must therefore ensure adequate mechanical properties as well as corrosion resistance at high temperatures in the long term. This product category comprises metallic and ceramic materials as well as intermetallic phases, which are classified between metals and ceramics. For achieving sufficiently high long-term creep resistance, the melting point of the basis elements for high-temperature materials must be at least 1400 °C. With the use of intermetallic phases as base material, the melting point of the phase is decisive. Furthermore, the metals must be available in sufficient quantity, and this requirement is reflected in the price.