Laser Welding, Additive Manufacturing Enable Equipment Refurbishments With Less Effort

The National Laser Centre of the Council for Scientific and Industrial Research (CSIR) has developed laser-based refurbishment techniques, including laser welding and additive manufacturing, that have made it possible to refurbish equipment that would otherwise have had to be scrapped or previously required much more effort, according to Herman Burger, the Centre's research group leader for laser material processing.

Leaking water tanks at the Koeberg nuclear power plant in the Western Cape of South Africa were refurbished with laser cladding technology, at far less than the estimated R1bn replacement cost.

Laser surface welding technology has increased service life and lowered the ownership costs of continuous caster rolls at the ArcelorMittal factory in Vanderbijlpark, South Africa.

CSIR's capability ensures that expensive repairs performed overseas in the past are now done in the country. "Both MAN Diesel and Turbo and Tupperware used to send components to Germany and Belgium, respectively, when laser cladding was required," Burger says. "Large, heavy components were shipped to the other side of the world to have a few kilograms of weld metal deposited by laser. It was extremely wasteful in terms of time, transport costs, and European labor rates. Now, it is done here."

MAN Diesel and Turbo projects and sales manager Christo du Plooy says rotating parts on machinery would traditionally have been repaired with metal spraying or submerged arc welding. The cost of laser refurbishment is high, but he believes that as the technology matures, its cost-effectiveness will increase.

The National Laser Centre also welds rocket motor casings for Denel Munition. Laser welding is used to produce cyclotron radiation targets for the production of radio isotopes for iThemba Labs.

Lasers extend the service life of industrial components by improving oxidation and corrosion resistance, and increasing resistance to abrasive wear—leading to massive savings.

Laser cladding is a weld overlay process in which a coating is placed on a worn metal surface—restoring and sometimes improving components. A high-power laser generates a small puddle of molten metal, called a weld pool, on the surface in need of repair.

Metal powder is then injected into the pool and when the laser beam and the powder mix, a new layer of metal is created and bonded to the old metal, creating robust adhesion.

Last year CSIR engineers designed a mobile system based on this technology, used to repair high-value components on site.

The other application of laser surface modification is laser hardening. A laser beam rapidly heats the surface layer of a carbon steel component. The new layer created hardens after rapid cooling. The CSIR has developed laser hardening processes for the armaments industries, Daimler Chrysler, and Bell Equipment.

Lasers are used for additive manufacturing, similar to 3D printing. Laser beams fuse metal powders together, layer by layer, to produce a fully functional part from computer-aided design data.

"Laser additive manufacturing is particularly advantageous where high-value components are manufactured from expensive and difficult-to-machine materials," says Burger. "Arguably, the biggest advantage of additive manufacturing is that it allows component design to be optimised for functionality rather than manufacturability."

The CSIR is in partnership with aeronautical engineering company Aerosud, which is focusing on the development of technologies that will enable high-speed production of large components. The project is funded by the Department of Science and Technology.

"We already use 3D printing for the manufacture of aircraft parts in plastics, such as air conditioning ducts. However, laser additive manufacture is a totally new technology for us. We are now developing a first pilot plant, so the technology will only be mature enough for production in three to four years," says Aerosud MD Paul Potgieter.