Thermal spraying can increase sustainability

Scientists and companies around the world are working hard to develop sustainable solutions within a variety of product fields. Thermal spraying can be one of the solutions. Simply put, thermal spraying means coating parts with a new surface layer, improving their functionality and making them more durable.

After nearly 30 years of applied research, University West has some of the world’s leading researchers within thermal spraying. They are frequently invited to international conferences and people from all around the world follow their research results.

For many years the research in thermal spraying at University West was focused on aero and industrial gas turbine engines. Today, roughly ten scientists are working on many more applications involving new materials and techniques. University West was the first academic institution in Europe to acquire equipment for research within axial suspension plasma spraying, and today is at the forefront of this field. Nicolaie Markocsan, Professor in Production Technology, is one of the scientists doing research on suspension spraying of coatings for different applications.

Cheaper fuel cells for mobile and stationary units

– Suspension spraying creates new possibilities and advantages. By spraying suspensions of various materials i.e. nano-sized powder in water or alcohol on a surface, we can design layers with unique microstructure and properties. We can create coatings that have either columnar or lamellar structure, are porous or dense, rough or smooth, thin or thick, with or without gradient composition, etc., depending on the given application, Prof. Markocsan explains.

– Producing Solid Oxid Fuel Cells (SOFC) with suspension spraying is cheaper and easier to scale-up to industrial production than the techniques often used today. The produced SOFCs also make it possible to employ a wider range of fuels than PEM fuel cells, which lowers the cost of the resulting electricity. 

– Because fuel cells are relatively expensive to produce with today’s techniques, the new thermal spray approach could open new possibilities for sustainable fuel cells in the vehicles of tomorrow. Other potential areas of use of fuel cells are mobile power plants and residential heating systems.

Greener combustion engines

Traditional diesel engines can also become more environmentally friendly by using thermal spraying. By coating certain parts of the engine, you can increase the efficiency of the engine and lower fuel consumption. Nicolaie is currently running a research project on this topic together with Scania, Volvo Cars and Volvo Trucks.

– The coated engine parts can also better cope with the new fossil free fuels that are entering the market. These types of fuels may pose new functional demands to the engine parts exposed to combustion. 

More efficient jet engines and power plants

To make gas turbines in jet engines and power plants greener they must be able to operate at higher combustion temperatures. The solution is to coat the exposed parts with efficient thermal insulating layers. That allows a more efficient burning of the fuel which leads to significant benefits in terms of lower fuel consumption and lower CO2 emissions.

Lightweight and durable brake discs

Brake discs are usually made of steel alloys that can be regarded as heavy (due to their higher thickness) and easy to release pollutant particles, which especially in big cities are causing serious environmental issues. Thermal spraying can provide the solution. Thinner and lighter materials can be employed for discs and by coating them with advanced materials, e.g. composites and/or ceramics they can have better functional properties and are more durable.

Surface technology with many areas of use

Nicolaie and his colleagues are also studying other areas of application.

– There are infinite ways to improve products and increase their durability by using thermal spraying. With different materials and methods, you can design coatings with new characteristics, to fit a certain purpose.

Examples of possible applications:

• Implants can be coated with biocompatible layers that may lead to an increased acceptance and osseo-integration in the human body e.g. titanium screws, hip or knee joints etc. University West and VIT University in India have conducted research on this topic.
• Water containers coated with a photocatalytic layer can clean polluted water. This could be very useful in areas where fresh water is hardly accessible. Researchers at University West have worked with the Fraunhofer Institute (IWS) in Dresden on photocatalytic coatings.
• Parts often subjected to freezing temperatures can be coated with a water repellent (superhydrophobic) layer to prevent/reduce ice formation. Superhydrophobic coatings could be useful in the aviation industry, offshore industry and wind power industry.    

This is thermal spraying

Thermal spraying is used to produce coatings on parts to give them new characteristics and functional performances. This technology can be used for production of new products but also for repair and maintenance.

In thermal spraying, powder particles are rapidly heated and propelled onto a surface at high speeds. When the molten or semi-molten particles reach the surface, they deform to “pancake” like splats. The continuous overlapping of the impinging particles/splats leads to coating formation that “grows” as long as spraying is done. The microstructure and characteristics of the formed coating can be controlled by adjusting the velocity and the temperature of the in-flight particles.

The materials used are mainly metal, metal alloys, composite materials, ceramics and polymers. These materials, in powder form, can be mixed with a liquid and used in suspension spraying.

Contact: Nicolaie Markocsan, Professor in Production Technology at University West, Sweden. E-mail: nicolaie.markocsan@hv.se