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The CSIR is involved in fundamental research and process development based on laser materials processing with specific reference to laser welding and cladding. The laser materials processing group provides South African industry with solutions to improve component lifetime and ultimately increase competitiveness.
Corney van Rooyen is a metallurgical/welding engineer at the CSIR National Laser Centre in the laser materials processing research unit. He focuses on laser welding and modifying surface properties of metals through laser metal deposition of a metallurgically-bonded surface layer. Metallurgy is the domain of materials science that studies the physical and chemical behaviour of metallic elements, their intermetallic compounds, and their alloys. It is also the technology of metals – ‘the way in which science is applied to their practical use’.
Van Rooyen says, “Laser-based welding processes are about exploiting the special characteristics of the laser as a heat source in order to realise benefits in tool repair, refurbishment and joining of components that can’t be achieved with conventional processes. With laser cladding, metal can be deposited with precise control and repeatability and superior properties are obtained due to the rapid solidification of the process. The latter is the result of the low heat input for which laser processing is known. My efforts are focused on welding metallurgy and understanding the unique material properties that result from laser cladding of alloys. The research is then applied to optimise process parameters such as laser power, welding speed or the type of filler material for industrial applications.
“Our current research is specifically focused on the modification of martensitic stainless steel during laser cladding to improve oxidation, corrosion and wear resistance, whereas process development is focused on novel laser-based repair and refurbishment processes,” he says. Martensitic stainless steels are extremely useful engineering materials and are thus highly useful to various industries.
Van Rooyen says, “The fundamental property of laser welding is the highly localised heat input that a focused laser beam delivers. This feature enables the high welding speeds and exceptionally low heat input for which laser welding is renowned. Weld
quality is assured through the unparalleled control that the laser welding process offers. The precision and control with which the laser delivers heat to the process is at the heart of its many important advantages.”
Van Rooyen says the CSIR National Laser Centre laser materials research group focuses specifically on the following: -
Laser welding of aluminium alloys, specifically semi-solid casting of aluminium alloys; dissimilar metals; and titanium alloys
- Laser joining of metal components utilising powder consumables
- Pulsed laser welding as a low heat input solution in joining of small and heat sensitive components.
In addition, Van Rooyen is involved in laser metals deposition, primarily:-
The improvement of oxidation, corrosion and wear resistance of laser-cladded martensitic stainless steel
- stablishing the capability to perform laser metal deposition of magnesium and generative near-net shape build-up of nickel-base, cobalt-base and titanium-base aerospace alloys
- Developing 3D laser cladding as a surfacing, refurbishment and generative build-up technology
- Developing mobile laser cladding technology for the surfacing and repair of large components.
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“Excellence is an art won by training and habituation. We do not act rightly because we have virtue or excellence, but rather we have those because we have acted rightly … Excellence then is not an act but a habit”. Those are the words of Aristotle, the Greek philosopher, scientist and physician, and are highly applicable to Van Rooyen.
Van Rooyen recently had an article published in the prestigious publication Welding in the World. This is the official mouthpiece of the International Institute of Welding (IIW), which is the leading organisation in the world in the field of the advancement of welding technology. Its members include experts in all the disciplines of welding and related technologies. The IIW organises regional conferences, as well as an annual general assembly. The best presentations from these conferences are selected for inclusion in Welding in the World. Van Rooyen says, “I feel honoured that my work was selected by a publication of this standard.”
At the 2008 CSIR National Laser Centre Excellence Awards, Van Rooyen received the Outstanding Contribution by an Individual Award. The quality, versatility and volume of his output are what have clearly impressed his management. Van Rooyen’s contribution spans the entire value chain from research papers, invention disclosures, process development, technology demonstrators and industrial support with specific reference to laser metal deposition.
In addition, Van Rooyen and two of his colleagues received the 2008 Contribution to Socio-Economic Development Award for developing and implementing an innovative and novel joining technology. This concept has made a significant contribution to the ability of clients to develop state-of-the-art products for which the international aerospace market has already displayed a strong interest.
Van Rooyen says, “I always wanted to become an engineer and metallurgy seemed interesting when I finished school. It is awesome to see what happens with steel during solidification and heat treatment. When I started working I decided to become a welding engineer. There is so much interesting metallurgy that happens during welding and dealing with laser welding makes it all the more exciting.”
Van Rooyen adds, “The CSIR has provided me with several opportunities to grow and develop my career through national and international collaborations, as well as the transfer of research efforts to industry. It is fulfilling to be able the apply knowledge to practical application so that our local industry can continue to prosper.”
CSIR Communication: Chiara Lincoln, email: Clincoln@csir.co.za
Technical enquiries: Corney Van Rooyen, email: CvanRooyen@csir.co.za
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