Multi-purpose parameter development for high productivity in Laser Powder Bed Fusion of IN718
Typ
Examensarbete för masterexamen
Program
Publicerad
2020
Författare
Panahi, Negar
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Laser-Powder Bed Fusion (L-PBF) is one of the main metal Additive Manufacturing
(AM) technologies that has seen major developments in terms of materials development,
applications, design and quality assurance, etc. One of the main limitations
of L-PBF process is the high cost of machine time dedicated to the production of
the parts. It is therefore desirable to speed up the process, making wide application
of the process more economically viable. In this thesis, we aim to increase the productivity
of L-PBF processing of IN718 by using a layer thickness (80 μm) which is
at least two times larger than the state-of-art (20 - 40 μm). An increase in the layer
thickness essentially decreases the amount of energy input by the laser beam to the
material per unit volume. Consequently, other process parameters including but
not limited to laser power, hatch distance, scanning speed, etc., shall be adjusted
accordingly to enable full densification of the part. Additionally, other aspects of
the product qualities should be considered during the optimization process, which
includes surface finish, geometrical compliance, and microstructure.
This thesis employs statistical Design of Experiments (DoE) and regression analysis
for the optimization of key L-PBF processing parameters. In the meantime, two
separate experimental campaigns were conducted using similar DOE matrix (central
composite design) but different sample geometries. In the first experimental
campaign, a simple cubic specimen was used, a processing window with optimized
combination of laser power, scan speed, hatch distance was determined using regression
analysis based on the measurements of relative densities from cross-sections. In
the second experimental campaign, more complex designs (staircase geometry) were
used to characterize the influence of heat accumulation effects at thin wall structures
on relative density and surface roughness. The applicabilities of volumetric
energy density (VED) and its normalised form for evaluation of process stability are
discussed.
Beskrivning
Ämne/nyckelord
Additive manufacturing , Laser powder bed fusion , Porosity , Powder layer thickness , IN718 , Scanning speed , Laser power , Hatch distance , Image analysis , Surface roughness