Atomization gases dependent mechanical properties in the laser powder bed fusion manufactured 304L stainless steel

Abstract

Clarifying the effects of the atomization gases on the mechanical properties and their interactions with scanning strategies is of vital importance in additively manufactured materials. In the present work, two batches of 304L specimens, i.e., N2-specimens and Ar-specimens, were produced by laser powder bed fusion using 304L stainless steel powders atomized by argon (Ar-powder) or nitrogen (N2-powder), respectively. The Ar-specimens have similar microstructures with finer grains, which do not change with the scanning strategies, while the N2-specimens have large-grained microstructures with textures varying with scanning strategies. The tensile test shows that the Ar-specimens have better consistency of mechanical properties, higher elongation, and higher strain hardening rates than that of the N2-specimens. While the tensile strength of the N2-specimens varies with the scanning strategies, in which the specimen with 67° laser scanning rotation has the highest tensile strength (694.80 MPa). Microstructural observation shows that the higher strain hardening rates of the Ar-specimens are caused by the simultaneous occurrence of deformation twinning and strain-induced martensite transformation, while the higher tensile strength of 67° rotation N2-specimen results from the texture-controlled Schmid factor (an average value of 0.45–0.47). This work may give guidance for the production of metal powders and for quickly tailoring the mechanical properties of the additively manufactured stainless steels.