University of Cambridge develops Laser-assisted cold spray (LACS)

A team from the University of Cambridge’s Centre for Industrial Photonics (CIP) has developed a new approach to cold spray additive manufacturing that integrates a laser to increase the efficiency of the process, particularly for high-strength aerospace materials like titanium and aluminum alloys. The innovative technology, called Laser-Assisted Cold Spray (LACS), could have applications in the repair of critical aerospace components, high-performance coatings and more.

The development of LACS came to be as the CIP team led by Professor Bill O’Neill was looking for ways to overcome the challenges of working with helium as a carrier gas for metal powder feedstocks. “Cold spray is a technique for rapidly fusing powdered metals, cermets (composites of ceramic and metal) or polymers without melting them, which can then be used for building, coating or repairing parts,” Professor O’Neill explained. “I first encountered cold spray while working at the University of Liverpool and set up my first facility dedicated to it there.

“At first, we concentrated on using nitrogen as a carrier gas for the powder. When working with high-strength materials such as titanium and aluminium alloys—commonly used in aerospace—we found that helium was essential for achieving optimal deposition. This is because helium, because of its lower molecular weight, enables higher particle velocities in cold spray, enhancing impact energy and improving adhesion to the substrate.”

While an effective carrier gas for these materials, the main issue with helium was related to the cost, which is about £80 per minute (roughly $110 USD). The team did explore the use of an innovative recovery system for the helium, however it could only recycle about 85% of the gas and limited the size of parts that could be made due to the chamber size of the recycling equipment. This, as the team pointed out, introduced challenges for aerospace applications in particular, which typically involve large components.

Searching for a solution to this issue, the team realized they could integrate a laser into the cold spray process. This laser selectively heats the deposition site to soften—but not melt—it as the high-strength powders are sprayed, which results in less substrate yield stress and a stronger bond between the substrate and coating or repair, all without the need for melting.

This approach offers a number of benefits compared to traditional cold spray additive manufacturing, including greater efficiency and stronger adhesion between the substrate and coating. Using the laser to soften the substrate also requires a lower particle velocity, which means that the original properties of the powder material are retained more effectively. This, as the team explains, is particularly advantageous when working with specialized materials like rare earth magnets and nano-structured coatings.

Other benefits of LACS include greater material compatibility, particularly when it comes to materials known for poor cold spray adhesion, like cermets, refractory metals and oxidation-resistant alloys; minimized residual stresses and porosity; fast deposition rates of up to 10 kg per hour; lower gas temperatures (in the range of 400–700°C vs up to 1200°C  for cold spray). These advantages are also on top of all the inherent benefits of cold spray AM in the first place, like the combination of multiple materials, reduced material usage and extending part lifespan.

“Developing a new generation of innovative manufacturing technology with advanced processing capabilities could significantly aid the transition to net zero,” added Prof O’Neill. “The ability to customize the properties of the materials is a real game-changer and has a huge range of potential applications; examples are producing lightweight components for electric vehicles and aerospace, creating hydrogen storage systems, enhancing wind turbine maintenance, manufacturing energy-efficient batteries and fuel cell components and developing advanced heat exchangers for industrial energy savings and catalyst coatings for carbon capture.”

In terms of applications, the technology has several uses, including the repair of components to extend part lifespan and accelerate MRO turnarounds, as well as to overcome logistical issues related to replacement part inventory and sourcing. “This is transformative for many industries, allowing custom parts to be created and repaired on demand in a short time frame, having low-cost, low-energy budget and efficient use of materials,” said Dr. Martin Sparkes, Principal Research Associate in the CIP lab. “We are excited to work together with industry partners to realize the potential of this unique and impactful technology.”

The LACS process could also be used to directly manufacture components, something that the engineering team is now exploring through the use of a mobile robotic arm. One of the challenges in doing this is to exert a high level of control over the shape of the powder deposition, so that parts have precise dimensions and smooth edges. “Currently, we have little control over the shape of deposition of the powder,” O’Neill added. “This is not an issue for coatings but presents a significant restraint for part-building applications.

“Our next goal is to find a solution to this limitation, and we already have some very promising results,” he concluded. “The potential applications for LACS are limitless and we are motivated to deliver a technology that can significantly aid in the transition to net zero, through both a more efficient, low-waste manufacturing technology and the doors it opens for sustainable product development.”