Instytut Podstawowych Problemów Techniki

Streszczenie:

Background Metal Laser Powder Bed Fusion Melting (LPBF-M) is considered economically viable and environmentally
sustainable because of the possibility of reusing the residual powder feedstock leftover in the build chamber after a part
build is completed. There is however limited information on the fatigue damage development of LPBF-M samples made
from reused feedstock.
Objective In this paper, the stainless steel 316 L (SS316L) powder feedstock was examined and characterised after 25
reuses, following which the fatigue damage development of material samples made from the reused powder was assessed.
Methods The suitability of the powder to LPBF-M technology was evaluated by microstructural observations and measurements of Hall flow, apparent and tapped density as well as Carr’s Index and Hausner ratio. LPBF-M bar samples in three
build orientations (Z – vertical, XY – horizontal, ZX – 45° from the build plate) were built for fatigue testing. They were
then subjected to fatigue testing under load control using full tension and compression cyclic loading and stress asymmetry
coefficient equal to -1 in the range of stress amplitude from ± 300 MPa to ± 500 MPa.
Results Samples made from reused powder (25 times) in the LPBF-M process exhibited similar fatigue performance to fresh
unused powder although a lower ductility for vertical samples was observed during tensile testing. Printing in horizontal
(XY) and diagonal (ZX) directions, with reused powder, improved the service life of the SS316L alloy in comparison to
the vertical (Z).
Conclusions Over the 25 reuses of the powder feedstock there was no measurable difference in the flowability between the
fresh (Hall Flow: 21.4 s/50 g) and reused powder (Hall Flow: 20.6 s/50 g). This confirms a uniform and stable powder feeding
process during LPBF-M for both fresh and reused powder. The analysis of fatigue damage parameter, D, concluded cyclic
plasticity and ratcheting to be the main mechanism of damage.

Słowa kluczowe:

SS316L ,Stainless steel,Fatigue,Additive manufacturing,Laser Powder Bed Fusion Melting (LPBF-M)

Afiliacje autorów:

Streszczenie:

Background

Metal Laser Powder Bed Fusion Melting (LPBF-M) is considered economically viable and environmentally sustainable because of the possibility of reusing the residual powder feedstock leftover in the build chamber after a part build is completed. There is however limited information on the fatigue damage development of LPBF-M samples made from reused feedstock.
Objective

In this paper, the stainless steel 316 L (SS316L) powder feedstock was examined and characterised after 25 reuses, following which the fatigue damage development of material samples made from the reused powder was assessed.
Methods

The suitability of the powder to LPBF-M technology was evaluated by microstructural observations and measurements of Hall flow, apparent and tapped density as well as Carr’s Index and Hausner ratio. LPBF-M bar samples in three build orientations (Z – vertical, XY – horizontal, ZX – 45° from the build plate) were built for fatigue testing. They were then subjected to fatigue testing under load control using full tension and compression cyclic loading and stress asymmetry coefficient equal to -1 in the range of stress amplitude from ± 300 MPa to ± 500 MPa.
Results

Samples made from reused powder (25 times) in the LPBF-M process exhibited similar fatigue performance to fresh unused powder although a lower ductility for vertical samples was observed during tensile testing. Printing in horizontal (XY) and diagonal (ZX) directions, with reused powder, improved the service life of the SS316L alloy in comparison to the vertical (Z).
Conclusions

Over the 25 reuses of the powder feedstock there was no measurable difference in the flowability between the fresh (Hall Flow: 21.4 s/50 g) and reused powder (Hall Flow: 20.6 s/50 g). This confirms a uniform and stable powder feeding process during LPBF-M for both fresh and reused powder. The analysis of fatigue damage parameter, D, concluded cyclic plasticity and ratcheting to be the main mechanism of damage.

Słowa kluczowe:

SS316L ,Stainless steel,Fatigue ,Additive manufacturing,Laser Powder Bed Fusion Melting (LPBF-M)

Afiliacje autorów:

Streszczenie:

In this paper, stainless steel 316L (SS316L) bars were additively manufactured (AM) in three orientations (Z – vertical, XY – horizontal, ZX45 – midway between vertical and horizontal) by using the Laser Powder Bed Fusion Melting (LPBF-M) method. The AM specimens were subjected to load control fatigue testing under full tension and compression (R = -1) at stress amplitudes ±350, ±400 and ±450 MPa. The XY and ZX45 printing orientations were found to significantly improve service life. Although similar strain response was found for each orientation when the same stress amplitude was applied, slightly different fracture mechanisms were identified during the post-mortem surface observations.

Słowa kluczowe:

SS316L,stainless steel,fatigue,additive manufacturing,Laser Powder Bed Fusion Melting (LPBF-M)

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Streszczenie:

Additive manufacturing (AM) is revolutionizing production with its ability to rapidly create complex designs while minimizing material waste. The influence of the SLM parameters on mechanical properties of two sets of open cell lattices (Set A and Set B) made of IN718 was investigated. The purpose of using the modified parameters was to reduce the cost/time of manufacturing as well as to reduce microporosity in ligaments by increased exposure time (reduced laser scanning speed) or higher energy density based on increased exposure time. The researchers investigate ligament deformation and collapse in porous lattices, its impact on overall behavior, and how microstructure influences hardening under varying strain rates.

Słowa kluczowe:

highly porous random open-cell lattice, additive manufacturing, direct impact Hopkinson pressure bar technique, Inconel 718

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Streszczenie:

Nowadays, additive manufacturing (AM) is revolutionizing production, enabling the rapid fabrication of objects in various sizes and shapes, including complex designs such as metallic foam, while significantly reducing material waste. This paper examines the effect of 3D printing parameters (Set A and Set B) on the mechanical behavior of a highly porous random open-cell lattice (HPROCL) in IN718 alloy produced by selective laser melting (PBF-LM). The modified build parameters were applied to reduce manufacturing cost and time while minimizing micro porosity in ligaments by increasing exposure time through reduced laser scanning speed or higher energy density. Furthermore, the researchers investigate ligament deformation, key stages of collapse and stability, its role in impact resistance, and how microstructure influences the hardening behavior of the HPROCL across a wide range of strain rates. The SEM-EDS elemental distribution analysis carried out on the tested specimens enabled to conclude that the foam printed with modified parameters (Set B) contained a lower content of the Laves phase and a higher amount of the δ-phase, which led to an increase in both static and dynamic compressive behavior of HPROCL in IN718 alloy.

Słowa kluczowe:

Additive manufacturing, Impact resistance, Highly porous random open-cell lattice, Inconel 718

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