Surface coatings from Zircotec have proved beneficial in applications such as automotive exhaust systems, where application to metallic components has reduced surface temperatures by over 170°C. Developments, however, mean these coatings can now be applied to composite materials, enabling their use in harsh environments.
Surface coating technology derived from the nuclear industry is enabling engineers to solve heat, wear and performance issues in a range of harsh environments.
When applied to metallic components, Zircotec’s plasma sprayed coatings have shown to reduce surface temperatures by over 170°C in some applications, such as automotive exhaust systems. Now, however, the company is offering solutions for new materials such as composites.
Coating the benefits
The coating is applied to the material using gas plasma spraying. For thermal barrier applications, molten material, primarily zirconica – which has a thermal efficiency of less than 1.7W/m K compared to 4W/m K for alumina – is fired at twice the speed of sound to the substrate over a proprietary nickel-based bond coat. The thickness, ranging from 250 to 400 microns, depends on the application and thermal barrier characteristics needed.
In laboratory testing on a V8 engine, the coating can reduce manifold surface temperatures by a third, with reductions from 600 to 473°C recorded. Once applied, the coating provides the heat resistance of lagging or wrap, yet requires no reapplication. Furthermore, being just microns thick it improves airflow around the component.
Such benefits have resulted in the technology being adopted by OEMs such as Lamborghini and Koenigsegg. They are, however, equally of interest to motorsport and car enthusiasts looking to manage heat and reduce underbonnet temperatures.
An exciting development for engineers is the use of the technology to enable composite materials to be used in harsh environments. This, explains the company, offers the ability to use materials where they previously could have melted.
Proven in F1, notably with great success to unlock performance gains with so-called blown diffusers in 2010, the technology is increasingly being used by other industries looking to gain the weight benefits of composites with better resistance to heat or wear. For wear, the solutions are metal based and for temperature they are ceramic, notably zirconia. According to Zircotec, the composite materials that can be coated include carbon fibre, sintered nylon and fibreglass.
“The environment is not always ideal for the use of composites,” said Peter Whyman, sales director. “This results in the use of heavier materials or bulky heat shields, which can reduce overall performance. The coating allows composites to function in temperatures above their melting point. Testing for a typical application gave a reduction in composite surface temperature of more than 125°C.”
For wear, Zircotec uses plasma sprayed metals such as molybdenum and stainless steel. “We can eliminate the need for heavy shielding or a requirement to continually replace the abraded surface sections,” said Whyman. “Crucially from a cost point of view, our coating is able to extend the life of the composite.”
For less harsh environments, ceramic coatings can be used. The company, for example, is trialling an ultra thin lightweight ceramic coating applied to the rims of carbon composite bicycle wheels to provide a tough, long lasting and durable braking surface that is capable of delivering exceptional levels of modulation even in wet conditions. The coating offers improved stopping distance and wet weather performance, and allows the use of standard hard-rubber brake materials in place of the specialist blocks normally used for carbon rims. Testing by a professional cyclist during a pre-season training camp demonstrated consistent and repeatable performance during 3400km of all-weather riding.
Alumina based ceramic coatings can offer both wear resistance and electrical insulation, at temperatures from 900°C down to cryogenic temperatures, and atmospheric to ultra high vacuum. Typically, a 100 micron alumina coating can stand off 10,000 volts.
Finding the solution
“Engineers have to find solutions to increase the efficiency of our vehicles, machinery and plant,” comments Whyman. “Coatings such as ours are providing answers to some of the issues that the newer materials raise and will enable those gains that are required by legislation or consumer demand.”