Tensile properties of 1100M high strength steel manufactured with laser directed energy deposition wire method

Abstract Laser directed energy deposition wire (L-DED-wire) process has gained profound interest due to its ability to fabricate relatively large parts with high productivity when compared to AM methods such as laser powder bed fusion, while wire-form material enhancing safety, storage and procurement aspects. Thus far, the utilization of ultra-high strength steels (UHSS) in L-DED-wire processing is only marginally covered in literature. L-DED-wire process has been shown to require precise control of multiple process parameters, which are predominantly interdependent. Deviations might result in inconsistencies during processing and in manufactured part quality. Accordingly, this study investigates the tensile properties of 1100M-class high strength steel material processed via L-DED-wire method. A wall structure was successfully fabricated and subjected to microstructural analysis and quasi-static tensile strength tests with machined coupons in two different orientations. The microstructural sample basis consisted of lath-shaped acicular ferrite; however the structure exhibited a recurrent pattern of bulky polygonal ferrite sections, which were expectedly credited to slowed down cooling rates of the upper layers. The tensile strength properties adequately matched the as-welded material specifications with isotropic behaviour among all samples; however, the existence of polygonal ferrite and inclusions negatively impacted the ductility of the vertical samples, resulting in brittle fracture mechanism. A moderate enhancement of tensile strength properties was seen with machined test coupons, as compared to their as-built equivalents.