Mechanical properties of DED-Arc steels: Statistical analysis and reliability implications for structural design

The complex thermal history inherent to the layer-by-layer wire-arc directed energy deposition (DED-Arc) process introduces challenges in predicting the mechanical properties of the printed material. A statistical evaluation of the tensile properties of DED-Arc steels using a database of 39 experimental studies, comprising over 400 yield and ultimate strength results across various wire grades and process conditions is presented. The results demonstrate that, for a given feedstock material, DED-Arc steels generally exhibit lower yield and ultimate strengths than the nominal properties of the welding consumables, with yield strength being particularly sensitive to the repeated thermal cycles and prolonged cooling times. Adopting a log-normal distribution, characteristic strength values are derived in accordance with EN 1990, revealing characteristic-to-nominal ratios of 0.75 for yield strength, with a typical COV of 0.12, and 0.93 for ultimate strength; this would result in the need for excessively high partial safety factors for DED-Arc structures. To address this, revised nominal strengths and corresponding strength classes, as well as a qualitative relationship between strength and t 8/5 cooling time are proposed to provide a foundation for the development of reliable structural design rules.