Full-size 3D-printed tungsten tiles have survived extreme heat inside a major nuclear fusion test reactor and emerged completely intact.
The protective components endured 74 direct plasma discharges inside the DIII-D National Fusion Facility in San Diego.
The tests subjected the tiles to three days of punishing particle bombardment in the machine’s exhaust zone, called the divertor.
During high-power runs, the tiles clocked roughly four minutes of direct plasma exposure.
This method uses a high-speed electron beam to melt tungsten powder layer by layer inside a vacuum chamber.
Electron-beam printing kept the metal above 2,552°F to prevent brittle cracking during fabrication.
Full-size 3D-printed tungsten tiles have survived extreme heat inside a major nuclear fusion test reactor and emerged completely intact. The protective components endured 74 direct plasma discharges inside the DIII-D National Fusion Facility in San Diego. The tests subjected the tiles to three days of punishing particle bombardment in the machine’s exhaust zone, called the divertor. During high-power runs, the tiles clocked roughly four minutes of direct plasma exposure. They even survived an accidental trial by fire when a neighboring, traditional tile melted and sprayed liquid metal across them. The printed surfaces held firm, proving the material can withstand the intense heat flux and particle bombardment driven by plasma that is hotter than the center of the Sun.
Tungsten is the premier choice to line future fusion power plants like ITER. It boasts the highest melting point of any metal at 3,422°C (6,191°F), more than twice that of steel. It is also exceptionally dense, weighing about as much as pure gold. Yet tungsten has long frustrated engineers. Below 600°C (1,112°F), the metal becomes brittle and shatters like glass under physical stress. “However, most attempts to 3D print tungsten, nearly all using lasers as the heat source for printing, have ended up porous and riddled with cracks,” said the team. Using a high-speed electron beam To overcome this hurdle, researchers turned to electron-beam powder bed fusion (EB-PBF). This method uses a high-speed electron beam to melt tungsten powder layer by layer inside a vacuum chamber. The beam sweeps across the powder bed quickly enough to keep the surrounding metal above 1,400°C (2,552°F) during the entire build. By keeping the build envelope red-hot throughout the process, the system prevents cracking caused by thermal shock and brittle cooling during fabrication.
While researchers proved the concept on small coin-sized samples in 2025, building reactor-ready components required an industrial scale-up. The final tiles needed to measure roughly 140 millimeters across and 20 millimeters thick. A joint team from North Carolina State University, Oak Ridge National Laboratory (ORNL), and Japanese precision manufacturer JEOL Ltd pulled off the leap in just eight months. JEOL fabricated the full-scale tiles on its large-format printer in Akishima, Japan. ORNL provided fusion materials expertise and project funding. Removing a critical bottleneck Once printed, the tiles were shipped to NC State for finishing. Engineers shaped the mounting fixtures using electrical discharge machining, an electrical wire-cutting method that introduces no mechanical strain. A computer-controlled grinder then removed roughly 250 microns from the surface, creating a mirror-like finish tailored to the divertor’s curved walls. The tiles were mounted on copper-alloy pedestals and bolted into the reactor for testing in July.
