Effect of heat input on phase content, crystalline lattice parameter, and residual strain in wire-feed electron beam additive manufactured 304 stainless steel

Structural and mechanical characterization of electron beam additive manufactured stainless steel samples has been carried out. The XRD measured austenite and ferrite lattice parameters showed their sensitivity to the heat input value, which was related to the chromium atom redistribution. The ferrite content depended on the heat input too. Optimal heat input level has been detected, which allowed obtaining the tensile strength higher than that of the base stainless steel. Residual strain levels in the as-deposited metal and fusion line zone have been measured using the X-ray sin²ψ method. The highest tensile residual strain was determined in a fusion line zone between the first as-deposited layer and a substrate. The microstructure of the first fusion line zone contained deformation twins and entangled dislocations generated by plastic flow under thermal expansion-contraction cycles.