Scientists weld glass and metal together
Scientists from Heriot-Watt University in Edinburgh, Scotland, have welded glass and metal together using an ultra-fast laser system. They consider the feat to be a breakthrough for the manufacturing industry.
Various optical materials such as quartz, borosilicate glass, and even sapphire were all successfully welded to metals like aluminium, titanium, and stainless steel using the Heriot-Watt laser system, which provides very short, picosecond pulses of infrared light in tracks along the materials to fuse them together.
A spiral weld is used as to demonstrate the new capability of welding glass and metal together developed at Heriot-Watt University.
The new process could transform the manufacturing sector and have direct applications in the aerospace, defense, optical technology, and even healthcare fields.
"Traditionally it has been very difficult to weld together dissimilar materials like glass and metal due to their different thermal properties -- the high temperatures and highly different thermal expansions involved cause the glass to shatter," says Professor Duncan Hand, director of the five-university EPSRC Center for Innovative Manufacturing in Laser-based Production Processes based at Heriot-Watt. "Being able to weld glass and metals together will be a huge step forward in manufacturing and design flexibility."
"At the moment, equipment and products that involve glass and metal are often held together by adhesives, which are messy to apply, and parts can gradually creep, or move. Outgassing is also an issue -- organic chemicals from the adhesive can be gradually released and can lead to reduced product lifetime," adds Hand.
The process relies on the incredibly short pulses from the laser. These pulses last only a few picoseconds; a picosecond to a second is like a second compared to 30,000 years.
"The parts to be welded are placed in close contact, and the laser is focused through the optical material to provide a very small and highly intense spot at the interface between the two materials. We achieved megawatt peak power over an area just a few microns across," says Hand. "This creates a microplasma, like a tiny ball of lightning, inside the material, surrounded by a highly confined melt region."
Hand says the welds were tested at -50C to 90C and they remained intact, so they are robust enough to cope with extreme conditions.
Microscopic "keyholes" formed in the metal during the laser process fill with molten glass and help to bond the two materials together.
Hand and his team are working with a consortium led by Oxford Lasers, a laser micromachining systems integrator, and laser specialists Coherent Scotland. Two end-users, Leonardo and Gooch & Housego, are helping to develop a prototype for the laser processing system and take it closer to commercialization. Two other partners, Glass Technology Services and the Center for Process Innovation, are helping to provide additional routes to commercialization, including the packaging of OLED devices.
Source: Heriot-Watt University
Published March 2019
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