Silicon carbide puzzle solved
No one has ever been able to process silicon carbide in such a way that it can be thermally sprayed as a lightweight, extremely durable coating on machine parts. That was before Fahmi Mubarok began his doctoral research.
“You could almost call this alchemy,” says Christian Gutvik, project manager at TTO, while we walk a long corridor in search of Fahmi’s office. “He has cracked the code that makes it possible to convert the raw material silicon carbide (SiC), into a coating, that can be thermally sprayed onto large machine parts. It’s the equivalent of going from coffee beans to coffee pods.”
Manufacturers that make jet engines and all kinds of turbines – from gas to wind to water – are always on the hunt for technological advantages that can increase performance and improve efficiency. Downtime for repairs and maintenance costs need to be low. The industry has small profit margins and to some extent, manufacturers are all competing for the best equipment. One important aspect is reducing friction in large machines, which is generally done by using an extremely hard, wear-resistant ceramic coating. The coating makes it possible for machines to be less susceptible to corrosion, more durable and withstand higher temperatures.
The best raw material
Silicon carbide is considered to be a miracle material when it comes to ceramic coating because of its unique properties. It is extremely hard but has a low density , which translates into lighter parts, and its characteristics make for very low friction. This combination results in higher performance at reduced cost and with less maintenance time.
But it has been impossible to use SiC as a thermal spray coating, even though everyone would like to. The problem is that the high temperatures generated during thermal spraying transform SiC from a solid to gas. That prevents the material from being used. And that is where Fahmi’s story begins.
He has developed a method that protects each SiC particle so that it does not become a gas while it is being sprayed. The technique makes it possible to apply many layers of SiC as a coating on large machine parts – like wind turbines. Fahmi’s PhD position received partial support from the Norwegian Research Centre for Offshore Wind Technology, also called NOWITECH, which is very interested in exactly this kind of engineering breakthrough.
Need for light, strong components
Wind turbine technology is developing at a furious pace. But at the same time this development is challenged by the increase in turbine size. Over the last three decades, for example, the power of a wind turbine has increased by a factor of more than 100. At the same time, the components installed in the nacelle, the long slender tube behind the turbine blades that encases the turbine itself, need to be as small and light as possible, which clearly calls for more durable components.
Offshore wind turbine technology poses its own additional challenge – that of access. Bad weather or long distances may make it difficult and costly to reach turbines to fix or maintain them. New, more durable coatings can increase component lifetime and reduced the need for maintenance, which in turn will also reduce the need to access the turbines, and thus cuts operation and maintenance costs.
“Many people have tried to achieve this breakthrough,” says Christian Gutvik. “Everyone knows this material has potential, many have tried to achieve that potential, but no one has succeeded, so this is ground-breaking.” Fahmi has now demonstrated that the patented technology works. From a conceptual standpoint, this is astonishing news.
Finding the solution through play
We have come to the laboratory where Fahmi has spent much of his time in recent years. It is in a small corner of a large hangar, where many other projects are underway.
“The method has actually tried before, but no one has succeeded,” says Fahmi. “I spent two years ‘playing’ with the same ingredients to find the optimal method for making the powder so that it can be applied with a thermal spray gun. It was also important to reduce the time it took. When I started, the process took three days.”
He can still remember the day in January 2011 when he and his colleagues first produced a good coating.
“We realized then that we had a way of making SiC sprayable,” he says, grinning broadly. Included in the “we” is his mentor, Nuria Espallargas.
What made Fahmi’s breakthrough possible is a chemical process that gives the raw material the characteristics it needs so it can be thermally sprayed.
“We’re now confident in the overall process. We will probably do some more fine-tuning, but we have other questions to address. One challenge that cropped up during development is the issue of the fineness of the powder. We want to have as fine a powder as possible, so that it flows like sand in an hourglass,” Fahmi said.
Fahmi found the solution to this particular challenge in his own kitchen.
“I looked at kitchen ingredients, such as cocoa powder and salt. While salt flows smoothly, cocoa powder is lumpy and uneven. I realized that the secret lies in the structure of each grain,” he said. Fahmi solved this problem, and shows us the powder – which flows evenly between his fingers.
Verified in many ways
Finding optimal parameters for both the powder and the thermal spray process are among the critical jobs that remain. The main key parameter is hardness, where the goal is to achieve a hardness that is equal to or better than tungsten carbide.
“It’s hard to find a clearer verification case than this,” says Gutvik. “The research is done, Fahmi and Nuria have demonstrated that their patented process prevents SiC from decomposing during thermal spraying. Now the industry is waiting for further verification, which is where the project stands now.”
The researchers received a total of NOK 1 million from NTNU Discovery. Last spring, they were awarded NOK 100 000 in pilot project funds to conduct a test in France to ensure that the results can truly be used in thermal spraying.
“But there is still a gap between us and the industry. Everyone we have been in contact with, whether exit candidates, partners or customers, wants proof that this works and that we are able to provide the market with the properties that people want. We can do that now with the help of the main project funds. We have long lists of questions from potential customers that we will try to answer after we have completed testing and verification.”
The project has also gotten recognition from the Research Council of Norway, where it was awarded NOK 2.9 million from the FORNY project. This is quite a substantial grant, and the gang is very enthusiastic about having a secure future. They already have interest from major industrial partners as well as established players and customers. But what they want first and foremost are pilot customers who are willing to be involved in testing the product. The market is well established with products that already exist.
“Our plans are to establish a company in 2014 and recruit some pilot customers, so that we can show good results by the end of 2015. Then we’ll see where things go from there,” says Christian Gutvik. Fahmi Mubarok is mainly interested in finishing his doctorate on the topic, and wants to pursue the product further. He has recently been awarded a postdoc so he can continue to develop the product along with TTO. “But I won’t be the one who runs the business,” he says with a smile.