Metal 3D printing extends the service life of steel components
Dübendorf, 25.06.2026 — Bridges, support structures, and industrial steel constructions are often subjected to stress for decades. As they age, fatigue cracks can compromise safety. However, replacing permanently installed components is often impractical or very costly. Empa researchers are therefore investigating how steel components can be specifically repaired or even redesigned in the future – using metallic 3D printing.
A thin crack runs through the steel plate. As the robotic arm moves over the weak spot, it creates not just a single weld seam, but a three-dimensional metal reinforcement. This is made possible by a process called Wire Arc Additive Manufacturing (WAAM). In this process, a welding wire is literally “printed” layer by layer onto defective areas using an electric arc.
Unlike traditional welding, metal 3D printing not only joins components together but also enables reinforcements with customized geometries and optimized production. This allows damaged areas to be reinforced locally and effectively without having to replace the entire defective component. Researchers at Empa aim to use this process to repair cracked parts of bridges and structural frameworks. This is because the permanently installed steel components are often difficult or very costly to replace.
Geometry is key, not the amount of material
“The key isn’t to apply as much material as possible,” explains Hossein Heydarinouri of Empa’s Structural Engineering laboratory. “The shape is much more important: An optimized geometry distributes stresses in such a way that the propagation of existing cracks is stopped or significantly slowed down.” For example, researchers from Empa and ETH Zurich were able to extend the service life of the damaged steel plates under investigation by up to four times as part of a master’s thesis project.
In extensive tests conducted in Empa’s construction hall, cracked steel plates were fitted with metal reinforcements of various shapes and then subjected to repeated loading. The results are clear-cut: All reinforced samples exhibited a significantly higher fatigue life than unrepaired control plates. Two-layer, stepped reinforcement geometries proved particularly effective.
At the same time, the study also highlights the limitations of the approach. If the geometry is chosen poorly, new stress concentrations can arise – for example, at the interfaces between the base material and the printed metal. “Our results show how important a targeted design of the reinforcement structure is,” says Heydarinouri.
Practical hurdles for on-site application
Fatigue cracks are among the most common types of damage in steel construction, and targeted reinforcement is significantly more efficient than completely replacing the damaged component. “Using 3D printing, we can apply metal reinforcements exactly where they are structurally needed,” says Heydarinouri. “Repairs save material, energy, and costs.”
Despite the great potential, the path to practical application is still challenging. Metal 3D printing is currently implemented using industrial robotic systems that are difficult to transport. “Damaged components are usually installed within the structure,” says Heydarinouri. “Today, they would have to be taken to a workshop for repair, which isn’t always realistic in practice.” While there are initial approaches for mobile or portable robotic systems, further developments are needed for widespread on-site use. Nevertheless, the research team sees advantages for applications where components are easily accessible or can be removed during maintenance work.
From repair to intelligent structural design
In addition to repairing damaged components, the team led by Empa researcher Heydarinouri is also working on more advanced concepts. The combination of intelligent geometries, metal 3D printing, and new materials enables metal structures that deliberately yield under extreme loads, absorbing energy in the process and then returning to their original shape as much as possible – or at least avoiding permanent damage. In future, they could be used as metallic damping elements for earthquakes or vibrations – for example, in bridges, buildings, or technical installations. Moreover, the Empa researcher sees potential in mechanical engineering, such as for lightweight yet highly stressed components in production machinery. WAAM really comes into its own particularly where only a few, geometrically optimized components are required. “3D printing gives us enormous geometric freedom,” says Heydarinouri. “We can specifically optimize structures – for example, to reduce weight while maintaining or even optimizing load-bearing capacity.”
In addition, Empa materials scientist Maryam Mohri is researching how shape memory alloys (SMAs) can be used to specifically enhance material properties. These “smart” materials have the ability to return to their original shape after being deformed – for example, by heating. In this way, improved material properties can be combined with customized geometries, opening up new possibilities for material-efficient and adaptive metal components. The corresponding geometries are developed at Empa using numerical simulations and then tested experimentally. The researchers thus ensure that the printed components meet realistic conditions and are suitable for industrial applications.
Further information
Dr. Hossein Heydarinouri
Structural Engineering
Phone +41 58 765 41 92
hossein.heydarinouri@empa.ch