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The magic of composites

NEW MATERIALS

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July 2018


Magic gold by Hublot, presented by Jean-Claude Biver

Author and co-author of over 180 scientific articles, two monographs and the holder of twelve patents, Professor Andreas Mortensen, vice president for research at Switzerland’s EPFL, runs the institute’s Laboratory of mechanical metallurgy (LMM) and teaches metallurgy and the mechanical behaviour of materials. In the following interview, he talks to us about his meeting with Jean-Claude Biver and the birth of “Magic Gold”.

“A

t the EPFL generally, and in our laboratory in particular, we not only conduct basic research, but also service the needs of local economies and society, which sustains us in our efforts.

We thus maintain natural relations with the surrounding industries and, as we are situated in the Lake Geneva area of Switzerland, we have developed regular ties with the watchmaking industry. The latter is naturally interested in our basic research work, but we also receive commissions from manufacturers, who hire us to conduct research work directly related to their business activities.

Ordinarily, they turn to us with specific queries, which they require us to solve if possible. With Jean-Claude Biver, then at the helm of Hublot, matters took quite a different course. He firstly presented himself, then he presented Hublot, explaining how his brand had “taken aesthetics to a whole new level” and how he intended to take them even further. He asked us about our ongoing research, showing particular interest in the combination of ceramic and metal.

I took him to be interested in our research work primarily for its application in watch finishes, and I ventured to suggest that we could do much more besides and that we’d like to “play around” a bit more, if he should feel so inclined.

We instantly clicked. We agreed on a vast field of exploration and, in an unprecedented move, he gave us total carte blanche. However, he was keen to emphasise one point: it had to make absolute sense on a scientific and technical level!

And, unlike with other managers of other industries, he attended our meetings in person at regular intervals. Several times, he said to us: “If you could make 18K gold scratch-resistant, then you’ll have found the Holy Grail!”

A researcher at the dedicated Magic Gold laboratory of the Hublot manufacture in Nyon, Switzerland
A researcher at the dedicated Magic Gold laboratory of the Hublot manufacture in Nyon, Switzerland

Modern-day alchemy

“To succeed in our efforts, we thought of using boron carbide, an extremely hard ceramic with high temperature stability. It is even used for its hardness properties in cladding applications, or in the internal panels of bulletproof vests, for example.

By combining a precious metal, 18K gold in this case, or an alloy containing a precious metal, with the boron- based ceramic, which has a melting point higher than that of said precious metal, a composite material is obtained, a fusion of metal with ceramic, giving a light (low density), extremely hard and thus virtually scratch-proof material harder than HV320, or even harder. This latter property is, in effect, especially useful for the application of this composite material in the watchmaking and jewellery industries.

Producing it is another matter. To reduce things to a simple level, first a flexible mould is filled with boron carbide at ambient temperature. The pre-formed boron carbide powder is then subjected globally to an isostatic pressure of 2,000 MPa.

“To succeed in our efforts, we thought of using boron carbide, an extremely hard ceramic with high temperature stability. It is even used for its hardness properties in cladding applications, or in the internal panels of bulletproof vests, for example."

After being preformed and removed from the mould, the powder is then sintered at a very high temperature to obtain the desired density while maintaining the interconnected porosity between the atoms, thereby creating a rigid, porous structure. Finally, the 24K gold alloyed with 3% molten liquid gold is injected under very high pressure with inert gas at a high temperature, allowing the metal to fill the ceramic pores.

Jean-Claude Biver
Jean-Claude Biver

The form thus obtained, in this case the watch bezel, must then be polished. This is no mean task given the hardness of the composite obtained, which can only be scratched by diamond. Finally, obtaining 18K gold certification was another complex undertaking, one that entailed separating the gold from the ceramic in order to weigh the gold and compare it with the initial weight of the material.

We succeeded in our undertaking and Hublot immediately announced the results. “Magic Gold”: the first scratch-resistant gold, boasting a Vickers hardness number of 1000 (compared to the 400 Vickers rating for traditional 18K gold or the 600 rating for hardened steel).

HUBLOT - MECA-10 Full Magic Gold
HUBLOT - MECA-10 Full Magic Gold

I must say I’m very impressed with the laboratory Hublot has just set up in its Nyon-based manufacture specifically for the production of Magic Gold. It’s a splendid facility.

What’s more, several of my former assistants and students have been recruited by LVMH either to work directly in Hublot’s laboratory, or to strengthen the team headed up by Guy Sémon, at his Research and Development lab in the LVMH watchmaking division.

Meanwhile, much remains to be done, many other combinations are possible in different materials. For gold alone, however, there is a lot more fun and experimentation to be had.

That said, innovation comes at a price! Many problems require solutions, and plenty of ideas are needed. Yet, the battle for new composites rages on and the researchers and scientists busy in the field continue to keep mum about the precise objective of the leads they are following. We too. A “new material” can be like gold dust.”