Ceramic dynamic

Could plasma spraying technology offer the ability to manufacture high-strength, lightweight, pure ceramic components? Justin Cunningham finds out.

Oxfordshire-based Zircotec is well-known in industry for its gas plasma spraying technology, which coats a thin layers of ceramic to a range of materials to improve their thermal properties.

Now, however, the firm is developing the process further to enable the production of pure ceramic components that eliminate the need for the original substrate altogether. With simple all ceramic tubular components already produced for use in very high temperature furnace applications, Zircotec believes the spraying process offers the opportunities for the manufacture of ultra light, heat resistant parts for other sectors.

Terry Graham, managing director at Zircotec, says: "We have a project to manufacture high-temperature ceramic susceptor tubes for use in the drawing of optical fibres. In this case, we apply a zirconia-hafnia mix. These tubes provide sealed containment within the furnace and are heated to temperatures of more than 2000°C. They can withstand long periods exposed to high temperatures before needing to be exchanged."

This innovation prompted the team to consider other applications for pure ceramic components. The benefits of using ceramic are well known by engineers, notably the ability to cope with extremely high temperatures. However, its brittleness often stops it being used in dynamic applications.

Moving from manufacturing simple tubes to creating more involved shapes is a significant step that presents many challenges. To overcome this, Zircotec suggest a ceramic matrix technology could be used. This would essentially layer a carbon fibre composite with the ceramic material to produce complex high strength, lightweight parts. Taking the technology to the extreme, it might even be possible to manufacture components as intricate as exhausts, brake ducts or aerospace components.

The process' specific requirements and the level of tolerance control Zircotec has achieved led it to consider migration to other sectors, although Zircotec's professional motorsport presence (notably in F1) means racing applications are seen as the first opportunity.

"We enjoy a close working relationship with most of the F1 teams, supplying heat resistant and anti-wear coatings," says Graham. "Through that work and F1's relentless quest to reduce weight whilst maintaining performance, it's become evident that our ability to create pure ceramic components could be of interest to design engineers."

Zircotec is only too aware of the harsh environmental challenges that an F1 car can present notably temperature, pressure and extreme vibration. As a firm whose technology has solved many issues in the nuclear field, Zircotec is cautiously optimistic that answers can be found. Although the technology is at an early stage, the interest shown by engineers leads the company to believe that the technology can find other niches.

The tubes are produced using a specially-constructed metal cylindrical former that enables high purity tubes from just a few millimetres up to more than 200mm in diameter with lengths of up to 2m possible. Crucially, however, to enable the applications to evolve, Zircotec is able to manufacture other non-tubular ceramic components.

Graham says: "Our experience means we can tightly control process parameters and feedstock to achieve a consistent, desired wall thickness, even creating interference fits for tubes to slide within each other."

Considerable experience, first derived from the UK's nuclear industry has led Zircotec to pioneer the specialised process for use in automotive, motorsport and industrial coating applications. The firm enjoys a tradition of technology transfer from the first motorsport application to it most recently being used as an anti-wear coating on the winches of this year's Volvo Ocean Race yacht. The blend of weight and performance potential suggests its latest ceramic forming technology is ikely to see use in other engineering sectors.

The high-performance coatings specialist unveiled a plasma sprayed ceramic and metal coating last month that included vanadium, a hard wearing composites surface coating. As well as its innovative ZircoFlex and ThermoHold coating for the protection of carbon composites.

Over 80% of teams competing in Formula One relied on Zircotec's surface coatings in 2011, with its ceramic thermal barrier technology a key feature of the exhaust blown diffuser utilised by many F1 teams to gain extra downforce.

"The technology was crucial for the teams who hadn't considered this in their initial design," said Peter Whyman, sales director at Zircotec. "Our coating reduces surface temperatures by 125°C and enable hot exhaust gases to pass over delicate carbon parts, protecting them from delamination."

Zircotec has taken the technology developed for motorsport applications and made it accessible to the mainstream automotive industry. Increasingly the coatings are being employed by further industries, particularly the defence sector, which is utilising ZircoFlex, a product that keeps crucial aspects of military vehicles cool in harsh environments.

"From our involvement in motorsport we have learnt to create lightweight parts that offer high levels of performance in harsh environments," says Whyman. "Many of these technologies are transferrable. We even have a road car project with a 'diffuser' that is coated with our Thermohold finish to prevent it being damaged by hot exhaust gases. We have also learnt to work faster. F1 deadlines mean we turn around parts in the day."

Justin Cunningham

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