Requirements on additives for tomorrow’s metalworking fluids

part 2

New materials

The performance, cost-effectiveness and resource efficiency of industrial products depend to a great extent on the materials that are used for their construction. For example, innovations in the material sector can save raw material and energy resources and also reduce environmental impacts. New materials are also of great importance with regard to future markets. The fields of application are broadly diversified, ranging from industries such as aeronautics or automotive engineering, optics, electronics, modern communication technologies and medical technology to architecture and construction. Several new materials are currently under development or are already used in a number of special applications.

Advanced high strength steels: Compared to conventional steels, advanced high strength steels (AHSS) include very complex phase microstructures resulting in very high tensile strength, good fatigue resistance and ductility. Thanks to their favourable properties they are particularly valued, for example, in car manufacturing because they lead to thinner wall thickness of components maintaining the same level of stability. This advantage can be translated into lower vehicle weight followed by lower fuel or energy consumption. Moreover the higher stiffness of structural elements made of AHHS results in higher safety because of better adsorption of crash energy. However, the improved mechanical properties lead to higher temperatures in the cutting process, increased tool wear and a raised tendency to cold welding in metalworking processes.

Superalloys: Superalloys are mainly nickel-based alloys (some are based on cobalt) characterised by high resistance to corrosion, even in the presence of sea water or strong acids, and also by excellent mechanical strength, resistance to thermal creep deformation, good surface stability, and resistance to high

temperature oxidation. They are known under the names Inconel, Hastelloy, Nimonic, Waspaloy, or Udimet. They are used in racing car engines, aircraft turbines, gas turbines, rocket engines, coal conversion plants, chemical and petroleum plants, and in many other applications that require heat and/or corrosion resistance. Most of the superalloys are very difficult to machine by cutting processes due to high ductility and the occurrence of work hardening. Because they are designed for high temperature applications they remain strong at machining temperature, their thermal conductivity is much less than that of steels. Some superalloys also contain abrasive intermetallic particles.

Titanium aluminides: Compared to nickel-based alloys, titanium aluminides show comparable resistance to high temperature oxidation up to approximately 800°C, but much lower density. Therefore they are used e.g. in some parts of aircraft turbines to reduce weight. Their low thermal conductivity as well as high abrasiveness and brittleness make them extremely difficult to machine.

Aluminium alloys: Because of their low weight and high strength some aluminium alloys are increasingly used in transportation and construction. Aluminium wrought alloys are specified by a four-digit number, where the first digit indicates the major alloying element. Particularly the 2000 and 7000 series aluminium alloys are used to replace steel components in aerospace, automotive, marine or railroad vehicles. The main alloying element of the 2000 series is copper. After a hardening process the strength of those alloys is comparable to steel. The alloys 2014A and 2024 e.g. are widely used in aircrafts. The 7000 series aluminium contains zinc as main alloying element and provides, after precipitation hardening, the highest strength of all commercially available aluminium alloys. A typical example is alloy 7068 which provides the highest mechanical strength of all aluminium alloys.

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