Temperature profile and melt depth in laser powder bed fusion of Ti-6Al-4V titanium alloy
Temperature profile and melt depth in laser powder bed fusion of Ti-6Al-4V titanium alloy
Luis E. Criales 0 1
Tug˘rul O¨ zel 0 1
Titanium 0 1
0 Manufacturing Automation Research Laboratory, Department of Industrial and Systems Engineering, Rutgers State University of New Jersey , 96 Frelinghuysen Road, Piscataway, NJ 08854 , USA
1 & Tug ̆rul O ̈ zel
In this paper, the prediction of temperature profile and melt depth for laser powder bed fusion (L-PBF) of Ti-6Al-4V titanium powder material was performed by numerically solving the heat conduction-diffusion equation using a finite difference method. A review of the literature in numerical modeling for laser-based additive metal manufacturing is presented. Initially, the temperature profile along the depth direction into the powder material is calculated for a stationary single pulse laser heat source to understand the transient behavior of the temperature rise during L-PBF. The effect of varying laser pulse energy, average power, and the powder material's density is analyzed. A method to calculate and predict the maximum depth at which localized melting of the powder material occurs is provided.
Lasers; Powder bed fusion; Thermal; Modeling
1 Introduction
Laser-based additive manufacturing (3-D printing)
technology has been rapidly growing and finding applications
in various industries including medical implants,
automotive and aerospace parts with complex geometries and
structures [
1
]. Specifically, laser powder bed fusion
(LPBF) processes such as direct metal laser sintering
(DMLSTM), selective laser melting (SLMTM),
LaserCUSINGTM, direct metal production (DMPTM), and laser
metal fusion (LMFTM) have been receiving a lot of
attention [
2
]. However, the build part quality and process
performance, structural integrity, mechanical properties and
related processing times are not at the desired
industryready levels. Predictive process modeling and optimization
for improved dimensional quality, product reliability, and
overall productivity are of great interest to the current,
ongoing research efforts [
3–7
]. This work gives a rapid
calculation technique for predicting temperature profile and
melt depth of metal powder material during laser melting.
It uses pulsed laser heat source to acquire transient
temperature behavior and enables studying the influence of
process input parameters and powder material properties
on the depth of melted material which is very practical for
industrial applications.
Selective laser melting is an additive manufacturing
process that directly and rapidly fabricates
three-dimensional parts by focusing and fully melting metallic powders
at selective locations and subsequently allowing for
solidification. In laser melting process, the powder material is
completely melted and solidified, as opposed to laser
sintering processes where metal powder material is sintered,
or partially melted [
5, 8, 11
]. Both groups of processes
utilize similar operational set-ups typically requiring a high
power fiber laser source, a beam delivery lens system, a
scanning mirror, a metal powder supply, a recoater roller or
blade, and a build platform, (see Fig. 1). When comparing
laser melting to other manufacturing techniques, the L-PBF
process has some clear advantages which can be listed as
(1) high flexibility in manufacturing complex shapes, (2)
quick process set-up avoiding the need for tooling, and (3)
high suitability for product customization and use of
different powder materials. These advantages allow for
quick transition between manufacturing products of
different geometries within the same station. The most
attractive feature of laser powder bed fusion is the ability to
use this process to produce highly complex geometries and
structures that would normally not even be feasible using
conventional manufacturing processes. However, laser
melting has a major disadvantage: the laser heating process
is known for its rapid heating times and unstable cooling
times, which result in the formation of pores and voids in
the microstructure, which often lead to reduced material
density and loss of dimensional accuracy and process
repeatability.
2 Literature review
Temperature distribution possesses a significant factor in
the resulting properties of the fabricated components using
laser powder bed fusion or laser cladding processes.
Therefore, accurately describing the temperature
distribution during and after the process is vital to obtaining
highquality samples. The temperature distribution for L-PBF
can be calculated using either an analytical solution
approach or a numerical solution approach. Furthermore, a
numerical solution can be obtained two-fold with a finite
element analysis (FEA) approach, and by means of
applying the finite difference method (FDM). L-PBF and
SLS processes use powder material which has different
thermal properties when compared to the bulk (fully dense)
material. Gusarov et al. [
9
] established a model to cal (...truncated)