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Thermal Operating Window in Selective Laser Melting Processes

Jerzy Kozak
Jerzy Kozak
, 
Tomasz Zakrzewski
Tomasz Zakrzewski
, 
Marta Witt
Marta Witt
 e 
Martyna Dębowska-Wąsak
Martyna Dębowska-Wąsak
   | 08 dic 2023
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Article Category: research article
Pubblicato online: 08 dic 2023
Pagine: 18 - 32
Ricevuto: 08 feb 2023
Accettato: 11 set 2023
DOI: https://doi.org/10.2478/tar-2023-0020
Parole chiave
© 2023 Jerzy Kozak et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1.

Additive manufactured GE9X engine components: (A) T25 sensor housing; (B) fuel nozzle tip; and (C) low-pressure turbine blades (adopted from reference [1]).
Additive manufactured GE9X engine components: (A) T25 sensor housing; (B) fuel nozzle tip; and (C) low-pressure turbine blades (adopted from reference [1]).

Figure 2.

Scheme of the fabrication stages: A – data preparation, B – manufacturing stage, C – the physical part (figures adopted from reference [2]).
Scheme of the fabrication stages: A – data preparation, B – manufacturing stage, C – the physical part (figures adopted from reference [2]).

Figure 3.

Schematic diagram of laser sintering melting (SLM) showing the key phenomena occurring during the process.
Schematic diagram of laser sintering melting (SLM) showing the key phenomena occurring during the process.

Figure 4.

The diagram of phases changes during energy input into powder. Point A with melting temperature Tm represents the lower thermal limit, and point B has temperature TB = Tb – ΔTB where TB is the upper thermal limit.
The diagram of phases changes during energy input into powder. Point A with melting temperature Tm represents the lower thermal limit, and point B has temperature TB = Tb – ΔTB where TB is the upper thermal limit.

Figure 5.

The scheme of the single-track melting and multitrack structures.
The scheme of the single-track melting and multitrack structures.

Figure 6.

The cross-sections of the tracks (A) simulation vs experimental sample. Track width at different laser travel speeds of (B) 1,050 mm/s, (C) 1,250 mm/s and (D) 1,450 mm/s (material: Ti-6Al; laser power: 175 W) (adopted from reference [8]).
The cross-sections of the tracks (A) simulation vs experimental sample. Track width at different laser travel speeds of (B) 1,050 mm/s, (C) 1,250 mm/s and (D) 1,450 mm/s (material: Ti-6Al; laser power: 175 W) (adopted from reference [8]).

Figure 7.

Schematic approximation of the cross-section by parabolic profile (A) and elliptical profile (B).
Schematic approximation of the cross-section by parabolic profile (A) and elliptical profile (B).

Figure 8.

Scheme of heating of the powder layer. Model dimensions: a, h, l.
Scheme of heating of the powder layer. Model dimensions: a, h, l.

Figure 9.

Thermal conductivity coefficient ke for the powder material for the solid and liquid phases.
Thermal conductivity coefficient ke for the powder material for the solid and liquid phases.

Figure 10.

The model of the bed layer and the used mesh (A); simulation of heating and melting of powder with a laser beam (B).
The model of the bed layer and the used mesh (A); simulation of heating and melting of powder with a laser beam (B).

Figure 11.

Plot of temperature distribution during heating P = 70 W, V = 1,200 mm/s. (cross-section perpendicular to the laser path; refer to Fig. 10).
Plot of temperature distribution during heating P = 70 W, V = 1,200 mm/s. (cross-section perpendicular to the laser path; refer to Fig. 10).

Figure 12.

Plot of the operating window and results of simulation and experiments.
Plot of the operating window and results of simulation and experiments.

Figure 13.

Simulation result of SLM at the following laser powers: (A) below lower thermal limit; (B) between lower and upper thermal limits; (C and D) exceeding the upper thermal limit. SLM, selective laser melting.
Simulation result of SLM at the following laser powers: (A) below lower thermal limit; (B) between lower and upper thermal limits; (C and D) exceeding the upper thermal limit. SLM, selective laser melting.

Figure 14.

The result of the SLM when the process is carried out under conditions that exceed the upper thermal limit (sample dimensions: 21 mm × 21 mm × 10 mm).
The result of the SLM when the process is carried out under conditions that exceed the upper thermal limit (sample dimensions: 21 mm × 21 mm × 10 mm).

Figure 15.

Plot of the operating window and results of simulation and experiments.
Plot of the operating window and results of simulation and experiments.

Figure 16.

The surfaces obtained through experiments carried out in conditions represented by points (1) and (2) in Fig. 15.
The surfaces obtained through experiments carried out in conditions represented by points (1) and (2) in Fig. 15.

Thermophysical properties and other parameters used in simulation.

Physical properties of the powder
Material density ρ 8,600 kg/m3
Specific heat capacity solid phase cs 390 J/kgoK
Specific heat capacity liquid phase cl 410 J/kgoK
Latent heat of melting Lm 334 [kJ/kg]
Melting temperature Tm 1,380 °C
Boiling temperature Tb 2,930 °C
Upper temperature margin ΔTB 30 °C
Emissivity ε 0.7
Process efficiency coefficient η 0.27

j.tar-2023-0020.tab.003

A Path cross-section area [m3]
C Specific heat capacity [J/kg·K]
H Powder bed thickness [μm]
ht Track height [m]
L Specific latent heat [J/kg]
ke Thermal effective conductivity of powder [W/mK]
kp Track section profile coefficient [-]
P Laser beam power [W]
Pd Hatch spacing [μm]
re Effective laser beam radius [μm]
Tm Melting temperature [K]
Tb Boiling temperature [K]
TA Lower temperature limit [K]
TB Upper temperature limit [K]
V Laser scanning speed [mm/s]
W Track width [m]
β Porosity
ρ Density [kg/m3]

Process parameters.

Parameters Lower limit Upper limit Unit
Laser beam power 70 170 W
Scanning speed 100 1,200 mm/s
Powder layer thickness 25 35 μm
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