scholarly journals Employment of an Extended Double-Integrating-Sphere System to Investigate Thermo-optical Material Properties for Powder Bed Fusion

2021 ◽  
Author(s):  
Thomas Schuffenhauer ◽  
Thomas Stichel ◽  
Michael Schmidt
Keyword(s):  
Optical Properties ◽  
Material Properties ◽  
Integrating Sphere ◽  
Powder Materials ◽  
Powder Bed Fusion ◽  
Empirical Parameter ◽  
Powder Bed ◽  
Heating And Cooling ◽  
Preheating Temperature ◽  
Polyamide Powder

AbstractThe optical energy input during laser-based powder bed fusion of polymers (PBF-LB/P) is influenced by a variety of process parameters (e.g., energy density) and powder material properties (e.g. optical properties, additives). Qualification of newly developed and/or modified powder materials still requires extensive, empirical parameter studies to assess processibility and find suitable process strategies. For powder characterization, a double-integrating-sphere system with an intervening hot stage, which allows accurate sample heating during the measurement of the optical properties, is presented and described. For qualification of the system and the associated characterization method for the PBF-LB/P process, the interaction of a collimated CO2 laser beam with selected polyamide powder materials during heating and cooling is investigated. The obtained results illustrate the suitability of the presented thermo-optical characterization technique, i.e., the temperature-dependent measurement of radiation reflected by and transmitted through the samples, for the systematical investigation of material-related (i.e., additives) and process-related (i.e., preheating temperature, layer height) influences on the beam-matter interaction.

scholarly journals Process characterization and analysis of ceramic powder bed fusion

2021 ◽  
Author(s):  
Kevin Florio ◽  
Dario Puccio ◽  
Giorgio Viganò ◽  
Stefan Pfeiffer ◽  
Fabrizio Verga ◽  
...  
Keyword(s):  
High Speed ◽  
Ceramic Powder ◽  
Integrating Sphere ◽  
Alumina Powder ◽  
Powder Bed Fusion ◽  
Single Track ◽  
Ceramic Powders ◽  
Pure Alumina ◽  
Powder Bed ◽  
Melt Pool

AbstractPowder bed fusion (PBF) of ceramics is often limited because of the low absorptance of ceramic powders and lack of process understanding. These challenges have been addressed through a co-development of customized ceramic powders and laser process capabilities. The starting powder is made of a mix of pure alumina powder and alumina granules, to which a metal oxide dopant is added to increase absorptance. The performance of different granules and process parameters depends on a large number of influencing factors. In this study, two methods for characterizing and analyzing the PBF process are presented and used to assess which dopant is the most suitable for the process. The first method allows one to analyze the absorptance of the laser during the melting of a single track using an integrating sphere. The second one relies on in-situ video imaging using a high-speed camera and an external laser illumination. The absorption behavior of the laser power during the melting of both single tracks and full layers is proven to be a non-linear and extremely dynamic process. While for a single track, the manganese oxide doped powder delivers higher and more stable absorptance. When a full layer is analyzed, iron oxide-doped powder is leading to higher absorptance and a larger melt pool. Both dopants allow the generation of a stable melt-pool, which would be impossible with granules made of pure alumina. In addition, the present study sheds light on several phenomena related to powder and melt-pool dynamics, such as the change of melt-pool shape and dimension over time and powder denudation effects.

scholarly journals Effects of Positioning Conditions on Material Properties In Powder bed Fusion Additive Manufacturing

2021 ◽  
Author(s):  
Mevlüt Yunus Kayacan ◽  
Nihat Yılmaz
Keyword(s):  
Additive Manufacturing ◽  
Material Properties ◽  
Layer By Layer ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Cooling Rates ◽  
Powder Bed ◽  
Manufacturing Technologies ◽  
Average Size ◽  
Hardness Values

Abstract Among additive manufacturing technologies, Laser Powder Bed Fusion (L-PBF) is considered the most widespread layer-by-layer process. Although the L-PBF, which is also called as SLM method, has many advantages, several challenging problems must be overcome, including part positioning issues. In this study, the effect of part positioning on the microstructure of the part in the L-PBF method was investigated. Five Ti6Al4V samples were printed in different positions on the building platform and investigated with the aid of temperature, porosity, microstructure and hardness evaluations. In this study, martensitic needles were detected within the microstructure of Ti6Al4V samples. Furthermore, some twins were noticed on primary martensitic lines and the agglomeration of β precipitates was observed in vanadium rich areas. The positioning conditions of samples were revealed to have a strong effect on temperature gradients and on the average size of martensitic lines. Besides, different hardness values were attained depending on sample positioning conditions. As a major result, cooling rates were found related to positions of samples and the location of point on the samples. Higher cooling rates and repetitive cooling cycles resulted in microstructures becoming finer and harder.

scholarly journals Analytical Modeling of Residual Stress in Laser Powder Bed Fusion Considering Part’s Boundary Condition

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 337 ◽  
Author(s):  
Elham Mirkoohi ◽  
Hong-Chuong Tran ◽  
Yu-Lung Lo ◽  
You-Cheng Chang ◽  
Hung-Yu Lin ◽  
...  
Keyword(s):  
Residual Stress ◽  
Thermal Stress ◽  
Kinematic Hardening ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Repeated Heating ◽  
Powder Bed ◽  
Heating And Cooling ◽  
Body Load ◽  
Point Body

Rapid and accurate prediction of residual stress in metal additive manufacturing processes is of great importance to guarantee the quality of the fabricated part to be used in a mission-critical application in the aerospace, automotive, and medical industries. Experimentations and numerical modeling of residual stress however are valuable but expensive and time-consuming. Thus, a fully coupled thermomechanical analytical model is proposed to predict residual stress of the additively manufactured parts rapidly and accurately. A moving point heat source approach is used to predict the temperature field by considering the effects of scan strategies, heat loss at part’s boundaries, and energy needed for solid-state phase transformation. Due to the high-temperature gradient in this process, the part experiences a high amount of thermal stress which may exceed the yield strength of the material. The thermal stress is obtained using Green’s function of stresses due to the point body load. The Johnson–Cook flow stress model is used to predict the yield surface of the part under repeated heating and cooling. As a result of the cyclic heating and cooling and the fact that the material is yielded, the residual stress build-up is precited using incremental plasticity and kinematic hardening behavior of the metal according to the property of volume invariance in plastic deformation in coupling with the equilibrium and compatibility conditions. Experimental measurement of residual stress was conducted using X-ray diffraction on the fabricated IN718 built via laser powder bed fusion to validate the proposed model.

Laser-based powder bed fusion of 16MnCr5 and resulting material properties

2020 ◽  
Vol 35 ◽  
pp. 101372
Author(s):  
Matthias Schmitt ◽  
Tobias Kamps ◽  
Felix Siglmüller ◽  
Jakob Winkler ◽  
Georg Schlick ◽  
...  
Keyword(s):  
Material Properties ◽  
Powder Bed Fusion ◽  
Powder Bed

scholarly journals Improved Process Efficiency in Laser-Based Powder Bed Fusion of Nanoparticle Coated Maraging Tool Steel Powder

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3465
Author(s):  
Oliver Pannitz ◽  
Felix Großwendt ◽  
Arne Lüddecke ◽  
Arno Kwade ◽  
Arne Röttger ◽  
...  
Keyword(s):  
Tool Steel ◽  
Steel Powder ◽  
Process Efficiency ◽  
Powder Materials ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Laser Systems ◽  
Additional Improvement ◽  
Few Layer Graphene ◽  
The Impact

Research and development in the field of metal-based additive manufacturing are advancing steadily every year. In order to increase the efficiency of powder bed fusion of metals using a laser beam system (PBF LB/M), machine manufacturers have implemented extensive optimizations with regard to the laser systems and build volumes. However, the optimization of metallic powder materials using nanoparticle additives enables an additional improvement of the laser–material interaction. In this work, tool steel 1.2709 powder was coated with silicon carbide (SiC), few-layer graphene (FLG), and iron oxide black (IOB) on a nanometer scale. Subsequently, the feedstock material and the modified powder materials were analyzed concerning the reflectance of the laser radiation and processed by PBF-LB/M in a systematic and consistent procedure to evaluate the impact of the nano-additivation on the process efficiency and mechanical properties. As a result, an increased build rate is achieved, exhibiting a relative density of 99.9% for FLG/1.2709 due to a decreased reflectance of this modified powder material. Furthermore, FLG/1.2709 provides hardness values after precipitation hardening with only aging comparable to the original 1.2709 material and is higher than the SiC- and IOB-coated material. Additionally, the IOB coating tends to promote oxide-formation and lack-of-fusion defects.

scholarly journals Position-dependent mechanical characterization of the PBF-EB-manufactured Ti6Al4V alloy

2021 ◽  
Author(s):  
Daniel Kotzem ◽  
Alexandra Höffgen ◽  
Rajevan Raveendran ◽  
Felix Stern ◽  
Kerstin Möhring ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Material Properties ◽  
Mechanical Characterization ◽  
Industrial Applications ◽  
Fatigue Tests ◽  
Ti6al4v Alloy ◽  
Effective Diameter ◽  
Powder Bed Fusion ◽  
Powder Bed

AbstractBy means of additive manufacturing, the production of components with nearly unlimited geometrical design complexity is feasible. Especially, powder bed fusion techniques such as electron beam powder bed fusion (PBF-EB) are currently focused. However, equal material properties are mandatory to be able to transfer this technique to a wide scope of industrial applications. Within the scope of this work, the mechanical properties of the PBF-EB-manufactured Ti6Al4V alloy are investigated as a function of the position on the building platform. It can be stated that as-built surface roughness changes within building platform whereby highest surface roughness detected by computed tomography (Ra = 46.0 ± 5.3 µm) was found for specimens located in the front of the building platform. In contrast, no significant differences in relative density could be determined and specimens can be assumed as nearly fully dense (> 99.9%). Furthermore, all specimens are affected by an undersized effective diameter compared to the CAD data. Fatigue tests revealed that specimens in the front of the building platform show slightly lower performance at higher stress amplitudes as compared to specimens in the back of the building platform. However, process-induced notch-like defects based on the surface roughness were found to be the preferred location for early crack initiation.

Investigation of significant factors on deformation with powder bed fusion system

2020 ◽  
pp. 095440542097008
Author(s):  
Tan Pan ◽  
Lan Li ◽  
Xinchang Zhang ◽  
Aaron Flood ◽  
Sreekar Karnati ◽  
...  
Keyword(s):  
Powder Layer ◽  
Layer By Layer ◽  
Powder Bed Fusion ◽  
Geometric Accuracy ◽  
Success Rates ◽  
Powder Bed ◽  
Component Size ◽  
Heating And Cooling ◽  
Part Thickness ◽  
Significant Factors

Powder bed fusion (PBF) is one of the most popular techniques in additive manufacturing (AM). The PBF technique of selective laser melting (SLM) consolidates powder layer by layer using a laser as the energy source. This technique ensures the processes capability of fabricating components with internal and external complex geometries, which could be challenging to make with conventional manufacturing methods. However, the cyclic heating and cooling inherent in this process give rise to the buildup of residual stresses, which can distort or completely deform the part. In this work, a screening build with nine factors was designed to investigate the effects of component size, support structure, and energy input on the build completion and average distortion induced by the inherent residual stress. Experimental results indicated that support hatch spacing, part thickness, and support contact spacing played dominant roles in the final quality (i.e. resultant deformation) of the built parts. The identified significant factors from this study can be carefully selected to increase the success rates of single builds and improve the qualities (i.e. geometric accuracy) of the final products.

Powder Bed Fusion Additive Manufacturing of Ni-Based Superalloys

2020 ◽  
pp. 249-270
Author(s):  
Evren Yasa ◽  
Ozgur Poyraz
Keyword(s):  
Additive Manufacturing ◽  
Material Properties ◽  
Elevated Temperatures ◽  
Design Criteria ◽  
Complex Geometries ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Volume Production ◽  
Manufacturing Technologies ◽  
Aerospace And Defense

Emerging additive manufacturing technologies have been gaining interest from different industries and widened their fields of application among aerospace and defense. The introduction of powder bed fusion processes was one of the significant developments in terms of direct metal part manufacturing of different materials and complex geometries, presenting good properties, and decreasing the need for tooling to allow fast product development as well as small-volume production. In this respect, nickel-based superalloys are one of the most employed material groups for aerospace and defense applications due to their mechanical strength, creep, wear, and oxidation resistance at both ambient and elevated temperatures. Nevertheless, the use of some materials has not become widespread due to several reasons such as processing difficulties, absence of design criteria or material properties. This chapter presents a comprehensive benchmark for powder bed fusion additive manufacturing of nickel-based superalloys considering applications, characteristics, and limitations.

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