This study evaluates the effects of post-processing
annealing (900-1200 oC) and work hardening followed by recrystallisation
annealing on the microstructure and properties of laser powder bed fused (LPBF)
316L stainless steel, aiming to optimise its mechanical and corrosion
performance. As-built LPBF 316L exhibits a cellular microstructure with Cr/Mo
segregations, providing high strength and hardness. Annealing at 900-1050 oC
eliminates the cellular structure, reduces dislocation density, and forms
recrystallised grains, decreasing yield tensile strength (YTS) and hardness by
1.3-1.4 times while peaking ductility (total elongation 68 %) and impact
toughness (128 J/cm²) at 900 oC. However, higher temperatures (1200 oC)
moderately increase strength but significantly reduce ductility, toughness, and
corrosion resistance due to nano-sized (MnCrSiAl)O₃ inclusion precipitation and
transition to Mo-rich oxides, coarsening particles, and degrading the passive
film. Corrosion resistance is least affected at 1050 oC but remains inferior to
the as-built state. Prestraining (0.12 plastic strain) increases YTS by 1.2-1.7
times (to 690-699 MPa) and ultimate tensile strength by ~1.2 times (762-770
MPa) but reduces ductility by 1.5 times. Subsequent annealing at 900-1050 oC
induces recovery and partial recrystallisation, restoring ductility and achieving
a strength-ductility product of 40.3 GPa·%, though prior thermal stabilisation
hinders recrystallisation. All specimens exhibit ductile fractures with
fine/ultra-fine dimples. High-temperature annealing (900-1200 oC) fails to
comprehensively enhance properties (including corrosion resistance), suggesting
that as-built or prestrained-and-annealed LPBF 316L offers a better balance of
strength, ductility, and impact toughness for engineering applications.
Author(s) Details
Efremenko B.V
Pryazovskyi State Technical University, 49044 Dinpro, Ukraine.
Chabak Yu.G.
Pryazovskyi State Technical University, 49044 Dinpro, Ukraine and Institute
of Materials Research, Slovak Academy of Sciences, 04001 Kosice, Slovak
Republic.
Petryshynets I.
Pryazovskyi State Technical University, 49044 Dinpro, Ukraine and Institute
of Materials Research, Slovak Academy of Sciences, 04001 Kosice, Slovak
Republic.
Efremenko V.G.
Pryazovskyi State Technical University, 49044 Dinpro, Ukraine and Institute
of Materials Research, Slovak
Academy of Sciences, 04001 Kosice, Slovak Republic.
Please see the book here :- https://doi.org/10.9734/bpi/cmsrf/v5/6099
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