Nickel alloys and high temperature alloys in aircraft components

Since the development of the Nimonic alloys for Sir Frank Whittle’s first jet engine, Henry Wiggin Ltd, now part of Special Metals Corporation, has been involved with the design and improvement of aerospace nickel alloys (nimonic components and inconel components). Hastelloy components and Haynes high temparature alloys is the competition.

Whilst much of this work continues to be in relation to alloys for the high strength/high temperature applications of turbine blades, discs, seals, rings and casings of aero engines, aircraft nickel alloys are being utilised for other key aerospace engineering areas such as tooling for composite manufacture.

There have been four recent developments in aerospace nickel alloys, namely: disc alloys; low expansion superalloys; Inconel alloy 718SPF – a nickel base superalloy capable of being superplastically formed; Nilo (low expansion alloys) for composite tooling.

Copper alloys offer the properties needed for long-term safe aircraft operation. The design of an alloy to provide a closely targeted optimum property combination has become an increasingly sophisticated process.

Suppliers of high performance alloys must fulfil the stringent quality assurance requirements of the aerospace industry, and have intimate knowledge of alloy metallurgy/microstructure and resulting properties.

Copper-Nickel-Silicon

During the second half of this century wide use has been made of an alloy based upon copper and containing 2.0 to 3.5% nickel and 0.4 to 0.8% silicon. This precipitation-hardening alloy possesses high strength and good ductility combined with high electrical conductivity and thermal conductivity 40% that of copper.

Resistance to corrosion is excellent and the alloy has good anti-frictional and bearing properties. With a magnetic permeability <1.001, the alloy is essentially non-magnetic.

The versatility of this type of alloy is demonstrated by widespread use in diverse industry sectors. These applications include alloys for valve guides, piston tops and little end bushes in high performance internal combustion engines, aero-engine bearing cages, aircraft undercarriage components, gears and bushes, resistance welding electrodes, electrical contacts, piston crowns and plastics moulding dies.