Qualifying additively manufactured Eurofer97 reduced activation steel for fusion

An urgent challenge in the fusion industry is to find materials resistant to the temperatures, stresses, and irradiation doses present in most core designs. The forerunner structural materials are Reduced-Activation Ferritic/Martensitic Steels (RAFMS). There are multiple well-understood RAFMS grades such as Eurofer97 and F82-H fairly well suited to fusion applications. However, the fusion industry is looking for steels even more resistant to irradiation damage, with improved high-temperature properties (creep resistance, strength), as well as a supply chain able to deliver consistent parts made of such steels. One solution to this problem is to use additive manufacturing (AM), specifically laser powder bed fusion (LPBF), to manufacture legacy RAFMS. The advantages of AM are its short drawing-to-part timelines, the ability to scale from low to moderate volumes without extensive capital investment and the superior material properties. Our LPBF and heat treatment process for Eurofer97, yields ~40% higher yield strength at room temperature ~18% higher strength at 550 °C and an over 20-fold increase in creep rupture life relative to wrought Eurofer97 while keeping other relevant mechanical properties equivalent. Based on the potential of LPBF for improving RAFMS performance, we are now scaling up our manufacturing process. A key focus is the qualification of our material and manufacturing method. We are running an extensive experimental campaign to assess the effect of powder quality, in-spec deviations as well as provenance and LPBF process variability on material properties. We are also assessing the irradiation resistance of our material and generating an extensive dataset of mechanical properties (creep, tensile). We will present our methodology and the results obtained so far.