The benefits of thermal coating have already been
demonstrated in articifial joint replacements. Now
scientists are turning their attention to its potential
in water purification and solar energy collection.
Image: iStockphoto

Thermal spray coatings end up in some unexpectedly intimate places. On artificial hip and knee joints they can help people play a determined game of tennis. On tooth implants they give us extra bite. And in the fiery world of jet propulsion, when applied to turbine blades, thermal spray coatings improve fuel efficiency and extend engine life.

Research by Professor Chris Berndt was pivotal in the development of these joint and jet engine products, and remains a continuing interest of his. He is Professor of Surface Science and Interface Engineering at Swinburne University of Technology, where he is also director of the Industrial Research Institute Swinburne (IRIS).

Now, the science having been done, comes the task of equipping industry with people skilled in this constantly evolving technology. Professor Berndt’s research team is moving to a new unit in Swinburne’s TAFE division, signalling that the research will now also include training TAFE and higher education students in thermal spray technology to produce manufacturing engineers and technicians with coatings technology expertise.

The new facility will be the only university-based thermal spray lab in Australia. It will also simplify the steps needed by TAFE’s industrial partners to bring thermal spray problems to Professor Berndt’s group for solving.

For Australia’s still-developing coatings industry it means direct access to emerging technology. Richard Moore, CEO of United Surface Technologies, a Melbourne-based coatings company, says a lot of time is currently spent overseas keeping up with technical advances. “Having a world-class research and problem-solving group here in Melbourne is obviously a major advance for the industry,” he says.

Mr Moore’s company provides thermal spraying services for sectors including oil and gas, pulp and paper, cardboard products, printing, pumps and valves, mineral processing, automotive, medical, rail, and power generation. He says new coating technologies emerge each year, making it essential for the local industry to have access to developments, problem-solving expertise and trained graduates.

While many of today’s thermal spray applications are at the cutting edge of new manufacturing and materials processes, the world’s thermal spray research community actually celebrated the technology’s 100th anniversary in 2004.

Thermal spray is a coating process in which melted (or heated) materials are sprayed on to a surface. The heated particles strike the surface to be coated, and repeated overlaying builds up a coating of millions of now-solidified particles. Unlike some coating methods, thermal spray does not require a vacuum, which makes it cheaper. It is also faster than electroplating and vapour deposition. Many materials can be treated: metals, alloys, ceramics, plastics and composites. The typical coating thickness is 100 to 500 micrometres, the former being about the diameter of a human hair.

The main uses of thermal spray coatings are to control corrosion and provide protection from high temperatures. For example, they are used routinely on car components and in the large control valves on offshore oil platforms. Even concrete bridge structures can be protected from corrosion with thermal spray coatings of zinc.

Professor Berndt’s coatings for turbine blades allow them to run 100˚C hotter, lifting engine efficiency and saving fuel. “Even 0.5 per cent improvement in efficiency can save billions of dollars for commercial and defence organisations,” he says.

In his orthopaedic research, Professor Berndt developed an artificial bone coating for replacement joints and teeth. He says this bone-friendly ceramic material invites the creation of a “lovely sweet interface, as the natural bone knits with the coating, improving the body’s grip on the prosthesis”.

He expects thermal spray uses to increase. “I envisage an abundance of real-world applications,” he says. “These are likely to include water purification and solar energy collection. Solid oxide fuel cells are re-emerging, and long-life coatings will be essential in geothermal energy production.

“We can now design surface structures at the molecular scale for specific purposes. And we are experimenting with extremely thin surface spray coatings of only five micrometres. Our success will enable many new applications. For ultra-thin coatings, thermal spray could soon displace vapour deposition methods. I expect thermal spray to be a major solution for creating special surfaces, optimised for particular functions. The future is exciting.”