scholarly journals Influence of Process Conditions on the Local Solidification and Microstructure During Laser Metal Deposition of an Intermetallic TiAl Alloy (GE4822)

2021 ◽  
Vol 52 (3) ◽  
pp. 1106-1116
Author(s):  
Silja-Katharina Rittinghaus ◽  
Jonas Zielinski
Keyword(s):  
Heat Treatment ◽  
Additive Manufacturing ◽  
Process Parameters ◽  
Titanium Aluminides ◽  
Metal Deposition ◽  
Experimental Investigations ◽  
Process Conditions ◽  
Laser Metal Deposition ◽  
Melt Pool ◽  
Temperature Regimes

AbstractTemperature-time cycles are essential for the formation of microstructures and thus the mechanical properties of materials. In additive manufacturing, components undergo changing temperature regimes because of the track- and layer-wise build-up. Because of the high brittleness of titanium aluminides, preheating is used to prevent cracking. This also effects the thermal history. In the present study, local solidification conditions during the additive manufacturing process of Ti-48Al-2Cr-2Nb with laser metal deposition (LMD) are investigated by both simulation and experimental investigations. Dependencies of the build-up height, preheating temperatures, process parameters and effects on the resulting microstructure are considered, including the heat treatment. Solidification conditions are found to be dependent on the build height and thus actual preheating temperature, process parameters and location in the melt pool. Influences on both chemical composition and microstructure are observed. Resulting differences can almost be balanced through post heat treatment.

scholarly journals Correlations of Melt Pool Geometry and Process Parameters During Laser Metal Deposition by Coaxial Process Monitoring

2014 ◽  
Vol 56 ◽  
pp. 228-238 ◽  
Author(s):  
Sörn Ocylok ◽  
Eugen Alexeev ◽  
Stefan Mann ◽  
Andreas Weisheit ◽  
Konrad Wissenbach ◽  
...  
Keyword(s):  
Process Monitoring ◽  
Process Parameters ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Melt Pool

Melt Pool Temperature Control for Laser Metal Deposition Processes—Part I: Online Temperature Control

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Lie Tang ◽  
Robert G. Landers
Keyword(s):  
Temperature Control ◽  
Process Parameters ◽  
Process Model ◽  
Dynamic Balance ◽  
Metal Deposition ◽  
Time Varying ◽  
Laser Metal Deposition ◽  
Melt Pool ◽  
Melt Pool Temperature ◽  
Deposition Processes

Melt pool temperature is of great importance to deposition quality in laser metal deposition processes. To control the melt pool temperature, an empirical process model describing the relationship between the temperature and process parameters (i.e., laser power, powder flow rate, and traverse speed) is established and verified experimentally. A general tracking controller using the internal model principle is then designed. To examine the controller performance, three sets of experiments tracking both constant and time-varying temperature references are conducted. The results show the melt pool temperature controller performs well in tracking both constant and time-varying temperature references even when process parameters vary significantly. However a multilayer deposition experiment illustrates that maintaining a constant melt pool temperature does not necessarily lead to uniform track morphology, which is an important criteria for deposition quality. The reason is believed to be that different melt pool morphologies may have the same temperature depending on the dynamic balance of heat input and heat loss.

scholarly journals Additive Manufacturing of β-NiAl by Means of Laser Metal Deposition of Pre-Alloyed and Elemental Powders

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2246
Author(s):  
Michael Müller ◽  
Bastian Heinen ◽  
Mirko Riede ◽  
Elena López ◽  
Frank Brückner ◽  
...  
Keyword(s):  
High Temperature ◽  
Additive Manufacturing ◽  
Single Phase ◽  
Metal Deposition ◽  
Advanced Materials ◽  
Process Conditions ◽  
Elemental Distribution ◽  
Laser Metal Deposition ◽  
Preheating Temperature

The additive manufacturing (AM) technique, laser metal deposition (LMD), combines the advantages of near net shape manufacturing, tailored thermal process conditions and in situ alloy modification. This makes LMD a promising approach for the processing of advanced materials, such as intermetallics. Additionally, LMD allows the composition of a powder blend to be modified in situ. Hence, alloying and material build-up can be achieved simultaneously. Within this contribution, AM processing of the promising high-temperature material β-NiAl, by means of LMD, with elemental powder blends, as well as with pre-alloyed powders, was presented. The investigations showed that by applying a preheating temperature of 1100 °C, β-NiAl could be processed without cracking. Additionally, by using pre-alloyed, as well as elemental powders, a single phase β-NiAl microstructure can be achieved in multi-layer build-ups. Major differences between the approaches were found within substrate near regions. For in situ alloying of Ni and Al, these regions are characterized by an inhomogeneous elemental distribution in a layerwise manner. However, due to the remelting of preceding layers during deposition, a homogenization can be observed, leading to a single-phase structure. This shows the potential of high temperature preheating and in situ alloying to push the development of new high temperature materials for AM.

Simulation of laser cladding

2004 ◽  
Vol 120 ◽  
pp. 397-403
Author(s):  
J. Wilden ◽  
H. Frank ◽  
C. Theiler ◽  
T. Seefeld ◽  
G. Sepold
Keyword(s):  
Process Parameters ◽  
Titanium Aluminides ◽  
Elevated Temperatures ◽  
Injection Rate ◽  
Experimental Results ◽  
Laser Generation ◽  
Process Conditions ◽  
Directionally Solidified ◽  
Melt Pool ◽  
Feedstock Material

Nickel and titanium aluminides already show a high potential for use in lightweight applications at elevated temperatures; however, the strength of these intermetallics can be increased by directional solidification. These materials show a brittle behaviour at temperatures less than 600°C. Strength and ductility of aluminides are controlled by phase formation during solidification. The problem of crack formation had to be solved for laser rapid prototyping of intermetallics, and the process conditions for formation of directionally solidified structures have to be specified in order to generate directionally solidified TiAl parts properly. A model was developed to determine the influence of the process parameters on melt pool geometry, solidification time, and the formed structure. Temperature gradients and cooling rates were calculated using a simulation that also included feedstock material injection rate and process parameters. The experimental results were analysed using these simulations, and the process parameters were optimised so that crack-free laser-generated TiAl parts exhibiting a partially directionally solidified structure could be produced. The comparison of the simulated and experimental results led to process guidelines for laser generation of directionally solidified TiAl components.

scholarly journals Wire Laser Metal Deposition Additive Manufacturing of Duplex Stainless Steel Components—Development of a Systematic Methodology

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7170
Author(s):  
Amir Baghdadchi ◽  
Vahid A. Hosseini ◽  
Maria Asuncion Valiente Bermejo ◽  
Björn Axelsson ◽  
Ebrahim Harati ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Additive Manufacturing ◽  
Duplex Stainless Steel ◽  
Nitrogen Loss ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Geometrical Complexity ◽  
Systematic Methodology ◽  
Single Bead

A systematic four-stage methodology was developed and applied to the Laser Metal Deposition with Wire (LMDw) of a duplex stainless steel (DSS) cylinder > 20 kg. In the four stages, single-bead passes, a single-bead wall, a block, and finally a cylinder were produced. This stepwise approach allowed the development of LMDw process parameters and control systems while the volume of deposited material and the geometrical complexity of components increased. The as-deposited microstructure was inhomogeneous and repetitive, consisting of highly ferritic regions with nitrides and regions with high fractions of austenite. However, there were no cracks or lack of fusion defects; there were only some small pores, and strength and toughness were comparable to those of the corresponding steel grade. A heat treatment for 1 h at 1100 °C was performed to homogenize the microstructure, remove nitrides, and balance the ferrite and austenite fractions compensating for nitrogen loss occurring during LMDw. The heat treatment increased toughness and ductility and decreased strength, but these still matched steel properties. It was concluded that implementing a systematic methodology with a stepwise increase in the deposited volume and geometrical complexity is a cost-effective way of developing additive manufacturing procedures for the production of significantly sized metallic components.

Heat Treatment Design for IN718 by Laser Metal Deposition with High Deposition Rates — Modeling, Simulation and Experiments

2020 ◽  
Author(s):  
Chongliang Zhong ◽  
Venkatesh Pandian ◽  
Norbert Pirch ◽  
Andres Gasser ◽  
Gandham Phanikumar
Keyword(s):  
Heat Treatment ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Deposition Rates ◽  
Modeling Simulation ◽  
Treatment Design

Model Approach for Displaying Dynamic Filament Displacement during Impregnation of Continuous Fibres Based on the Theory of Similarity – Theory and Modelling

2021 ◽  
Vol 36 (4) ◽  
pp. 423-434
Author(s):  
F. Schulte-Hubbert ◽  
D. Drummer ◽  
L. Hoffmann
Keyword(s):  
Process Parameters ◽  
Similarity Theory ◽  
Dynamic Compaction ◽  
Experimental Investigations ◽  
Process Conditions ◽  
Scaled Model ◽  
Compaction Behavior ◽  
Thermoplastic Matrix ◽  
Analytical Foundation ◽  
Reinforced Thermoplastics

Abstract The underlying process for the production of textile reinforced thermoplastics is the impregnation of dry textile reinforcements with a thermoplastic matrix. The process parameters such as temperature, time and pressure of the impregnation are mainly determined by the permeability of the reinforcement. This results from a complex interaction of hydrodynamic compaction and relaxation behavior caused by textile and process parameters. The foundation for the description and optimization of impregnation progresses is therefore the determination of the pressure-dependent permeability of fibre textiles. Previous experimental investigations have shown that the dynamic compaction behavior during the impregnation of fibre reinforcements with thermoplastics or thermosets can be successfully characterized. However, for most cases, an analytical representation has not been possible due to the complexity of the process. Although it may be possible to reproduce this behavior by numerical calculations, the results need to be confirmed by experiments. This paper lays the analytical foundation for building a scaled model system, based on the theory of similarity, to observe, measure, and evaluate the dynamic compaction behavior of textile reinforcements under controlled process conditions.

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