The new welding process could transform the manufacturing sector, doing away with the need for adhesives, as well as increase durability and offer more design flexibility. The process would also have direct applications in the aerospace, defense, optical technology and even healthcare fields.
Professor Duncan Hand, director of the five-university EPSRC Centre for Innovative Manufacturing in Laser-based Production Processes based at Heriot-Watt, said: “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.”
The university has worked for several years on the concept of utilizing ultrafast (picosecond) pulsed lasers to directly join highly dissimilar materials combinations.
This type of welding was previously thought to be impossible due to the very large difference in thermal expansion coefficients and hence thermally-induced cracking, which often happens with glass welding.
The scientists also described another point in favor of ultrafast laser welding. It would help to convert laser manufacturing from a skilled assembly process to a much lower-cost automated manufacturing process.
The results prove out the concept
A number of materials, such as quartz, borosilicate glass, and even sapphire were successfully welded to metals like aluminum, titanium, and stainless steel using the Heriot-Watt laser system. The laser system provides very short, picosecond (one trillionth of a second) pulses of infrared light in tracks along the materials to fuse them together.
Professor Hand explains: “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.”
“This creates a microplasma, like a tiny ball of lightning, inside the material, surrounded by a highly-confined melt region. We tested the welds at -50C to 90C (-58F to 194F) and the welds remained intact, so we know they are robust enough to cope with extreme conditions.”
Heriot-Watt is based in a modern environment on the outskirts of Edinburgh, Scotland. Heriot-Watt hosts the EPSRC Centre for Doctoral Training in Applied Photonics, cementing Heriot-Watt’s reputation as a centre of excellence in photonics, and providing PhD students with an even more attractive environment for study, as well as enhanced training opportunities.
