Strengthening submerged-arc-additively-manufactured high-strength steel via in-situ carbon doping

In the present work, different additions of carbon powder were used in the fabrication of the high-strength steel by the submerged arc additive manufacturing (SAAM), and the microstructure and mechanical properties of the deposited specimens were characterized and discussed by the comparison with the specimen without carbon doping. The strengthening effects of the added carbon powder on the performance enhancement of high-strength steel were investigated. The results showed that the introduction of carbon powder promoted grain refinement. When adding 0.10 wt% carbon powder to the additive deposit, it was with no twinned martensite, but with the most significant grain refinement and the highest proportion of high-angle grain boundaries. The dislocation density increased and the highest strength reached 1030.8 MPa in that condition. The average ultimate tensile strength of the deposited specimen was increased by approximately 100 MPa compared with the deposited specimen without carbon doping. However, it had a decrease in the elongation. Combining the changes in strength and elongation, the major strengthening strategy was concluded to be dislocation strengthening.