Synchronous-hammer-forging-assisted laser directed energy deposition additive manufacturing of high-performance 316L samples

Abstract

Plastic-deformation-assisted method has positive effect on regulating microstructure and mechanical properties of additive manufacturing (AM) metal samples. However, when fabricating weakly rigid metal samples by laser directed energy deposition (LDED), there are great limitations in the applicability and process flexibility of the commonly used rolling deformation auxiliary methods, which needs to be further improved. In this study, a synchronous-hammer-forging-assisted laser directed energy deposition (SHLDED) method is developed, and the effect of synchronous-hammer-forging on the microstructure and mechanical properties of LDED-processed 316L stainless steel samples is investigated. The results show that large plastic deformation up to 21 % of deposited materials can be achieved using a small hammering force of 55 N. Compared with LDED sample, the microstructure of SHLDED sample shows obvious equiaxed grains and refinement effect. The maximum intensity of the pole figure decreases by 50 % and the average grain size decreases by 69 %. Owing to the combined effect of grain refinement and work hardening, the yield strength (YS), ultimate tensile strength (UTS), and microhardness of SHLDED sample reach 494 ± 19 MPa, 677 ± 7 MPa, and 243 ± 11 HV 0.2 , respectively, which are 41 %, 10 %, and 22 % higher than those of LDED sample. This study provides a new method for microstructure and mechanical properties regulation of LDED metal samples. • A synchronous-hammer-forging-assisted LDED device was developed. • 21 % large plastic deformation was achieved using small hammering force of 55 N. • The microstructure achieved 69 % grain refinement and 50 % anisotropy reduction. • The yield strength and tensile strength were improved by 41 % and 10 % respectively.