Feature Article A Passion for the Industry by Dr. David Ford
or some years I worked with a colleague to whom heaven was a factory, his mantra was to make the factory a place where people ran to work and walked home (rather than the other, more usual, way around). Unsurprisingly he was not wholly successful as his bailiwick was a monotonous machine shop. However, for our industry monotony is never a condition we are familiar with as we are forever fighting nature’s entropy, whose intention is to make life difficult by thwarting our efforts to make perfect castings each time. For thousands of years artisans appear to have been content to accommodate nature’s foibles and produced the most intricate of cast sculptures. The consistent success of the process left little need for major innovations. The second world war brought this technical complacency to an end, and with survival at stake, the art was urgently turned into a science. For the UK, the enlightenment
F
came following a visit in 1940 by the production manager of the Bristol Aero Engine company to the Austenal Laboratories to witness the lost wax process. The laboratory was included in a US tour to determine sub contract possibilities for the Hercules engine. The potential for this process was quickly realised and a political agreement was arranged to acquire the technology for the UK. By 1942 development foundries were set up at the Rolls-Royce and Bristol factories and the process was urgently applied to support the aircraft industry. The process was found to be ideally suited for the gas turbine engine and within a remarkably short time turbine and stator blades together with combustion chambers were produced. The potential for the process appeared boundless and engine designs and new high temperature materials were made
10 ❘ August 2021 ®
War time wax injection and casting development possible through the ‘cire-perdue’
process as it was originally known. The developments mentioned in
Figure 1 will be well known to readers of INCAST but it is worth revisiting those innovations that have had the most impact on the opportunities to exploit the technology. It is the development of these innovations that have given professional satisfaction to our scientists and engineers, and for many of us a lifetime passion for the industry.
Probably the most important
development since WW2 has been the introduction of vacuum melting and casting. The original furnaces used in the UK during the 1950s were roll-over vacuum arc furnaces, which although a marked improvement on air cast were inadequate for the advances in alloy development. The use of induction vacuum melting was a quantum leap and opened the door to the generation of superalloys based on nickel and formulated
for high temperature
strength and environmental resistance by the addition of up to twelve
elements. These developments culminated with the US Martin Marietta ‘DID’ alloys containing hafnium for high temperature ductility which in due course became invaluable for the future development of directional solidification.
During the 1960s casting research in the US and UK showed the potential advantage of directional solidification to create a metallurgical structure which had superior resistance to low cycle fatigue in gas turbines and with a higher internal integrity than conventional equiaxial grain castings. The increased resistance to LCF and thermal fatigue is a consequence of the reduced elastic modulus from the crystal structure in the longitudinal columnar grains. The impact of this technology on engine efficiency and reliability cannot be overemphasised and can be considered a triumph for our industry. The development and application
of the Hot Isostatic Pressing (HIP’ing) process can also be considered as a ‘life changing moment’, particularly
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