Selective laser melting of high strength and toughness stainless steel parts: The roles of laser hatch style and part placement strategy

Laser hatch style and part placement strategy are acknowledged to have a considerable effect on processing quality and mechanical performance of selective laser melting (SLM) products. In an effort to obtain 316L stainless steel products with favorable properties, hatch style integration and part placement optimization were adopted in this study. The tensile property of SLM parts at different placement angle ψ was identified and the corresponding deformation behavior and failure mechanism were investigated. Interestingly, the part prepared by double stagger melt (DSM) style presented a strong <001> texture along the transverse direction (TD) rather than the growth orientation of the columnar grains (building direction, BD). This crystallographic variation imposed an immense effect on yield strength of SLM-processed parts by modifying the orientation relationship between texture and growth direction of grains. As ψ was set to 60°, the DSM-fabricated parts exhibited a lower Schmid factor, hence achieving a higher average yield strength σs of 536.6 MPa. The static fracture toughness UT was closely associated with the normal component force Fn imposed on preferential loading plane. By means of hatch style integration and part placement optimization, the dangerous “opening or tensile” loading mode was effectively avoided and reasonable compromise between the strength and ductility was achieved elaborately, thus obtaining an ultrahigh UT (3.478 × 108 J/m3) of SLM-processed parts. This study scientifically showed the great potentials of the SLM process to prepare 316L stainless steel products demanding challenging high-strength and high-toughness performance.