Discrete Phase Modeling of the Powder Flow Dynamics and the Catchment Efficiency in Laser Directed Energy Deposition with Inclined Coaxial Nozzles

2021 ◽  
pp. 1-37
Author(s):  
Sachin Alya ◽  
Ramesh Singh
Keyword(s):  
Mass Flow ◽  
Energy Deposition ◽  
Flow Dynamics ◽  
Free Form ◽  
Powder Flow ◽  
Process Conditions ◽  
Directed Energy Deposition ◽  
Discrete Phase ◽  
Directed Energy ◽  
Inclined Nozzle

Abstract Laser Directed Energy Deposition (DED) is one of the most promising additive manufacturing processes for restoring high value components. The damaged components can have complex free-form shapes which necessitates depositions with an inclined nozzle, where, the gravity can adversely affect the powder flow dynamics and the powder catchment efficiency (PCE). PCE is defined as the fraction of the total mass flow rate entering the melt pool and a low PCE can render the process inviable. In this paper, the effect of nozzle inclination on the powder flow dynamics and resulting PCEs have been studied. It was found that the powder flow dynamics is altered significantly in an inclined nozzle and results in an asymmetric and skewed powder jet. This affects the powder focusing adversely and the PCE deteriorates rapidly with an increase in the inclination and falls below 20% at 75°. A discrete phase model has been developed to understand the powder flow dynamics at different inclinations and process conditions. The mass flow distribution asymmetry on the focal plane at various nozzle inclinations have been analyzed via the model. The model is able to predict PCEs at different nozzle inclinations with reasonable accuracy. It has been observed that carrier gas flow, particle size and laser diameter affect the PCE significantly and can be used to counter the enhanced powder loss at large nozzle inclinations. Process maps have been developed to identify the favorable, acceptable and low PCE regions for the selection of optimal DED parameters.

Parametric Study and Multi-Criteria Optimization in Laser Directed Energy Deposition of 316L Stainless Steel

2020 ◽  
Author(s):  
Samuel Kersten ◽  
Maxwell Praniewicz ◽  
Omar Elsayed ◽  
Thomas Kurfess ◽  
Christopher Saldana
Keyword(s):  
Energy Deposition ◽  
Base Material ◽  
Predictive Modelling ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Process Conditions ◽  
Material System ◽  
Multiple Parameters ◽  
Directed Energy Deposition ◽  
Directed Energy

Abstract Directed Energy Deposition (DED) is an additive manufacturing technique in which a heat source is used to generate a small pool of molten material while powder feedstock is fed into the melt pool to create tracks of raised material on the surface of a part. Given the appropriate process parameters for the chosen material system and process conditions, fully dense complex geometric features are able to be constructed. In order to generate a high quality clad, two main criteria must be met: sufficient bonding with the substrate with minimized dilution of the clad by the base material and minimal porosity. Track shape is a key indicator in determining the quality of the process. This paper evaluates the influence of several of the key processing parameters — laser power, scanning speed, and powder mass flowrate — on single-clad track morphology. An analysis of variance (ANOVA) is performed to evaluate the significance of the main input parameters and the interactions between multiple parameters. A second-order polynomial model is then fit to the data to allow for predictive modelling of track shape based on a set of inputs. Finally, a multi-criteria cost function is generated, and sequential quadratic programming is performed to solve the objective function. Through these operations, the correct combination of processing parameters can be selected in order to generate a cladded track with desirable geometric traits.

Effect of Process Parameters on Laser Directed Energy Deposition of Copper

2019 ◽  
Author(s):  
Sunil Yadav ◽  
Christ P. Paul ◽  
Arackal N. Jinoop ◽  
Saurav K. Nayak ◽  
Arun K. Rai ◽  
...  
Keyword(s):  
Process Parameters ◽  
Feed Rate ◽  
Laser Power ◽  
Energy Deposition ◽  
Process Conditions ◽  
Powder Feed Rate ◽  
Track Geometry ◽  
Powder Feed ◽  
Directed Energy Deposition ◽  
Directed Energy

Abstract Laser Additive Manufacturing (LAM) is an advanced manufacturing processes for fabricating engineering components directly from CAD Model by depositing material in a layer by layer fashion using lasers. LAM is being widely deployed in various sectors such as power, aerospace, automotive etc. for fabricating complex shaped and customized components. One of the most commonly used LAM process is Directed Energy Deposition (LAM-DED) which is used for manufacturing near net shaped components with tailored microstructure, multi-materials (direct and graded) and complex geometry. This paper reports experimental investigation of LAM of Copper (Cu) tracks on Stainless Steel 304 L (SS 304L) using an indigenously developed LAM-DED system. Cu-SS304L joints find wider applications in tooling, automotive and aerospace sectors due to its combination of higher strength, thermal conductivity and corrosion resistance. However, laying Cu layers on SS304L is not trivial due to large difference in the thermo-physical properties. Thus, a comprehensive experiments using full factorial design are carried out and a number of Cu tracks were laid on SS304L substrate by varying laser power, scan speed and powder feed rate. The laid tracks are characterized for track geometry and porosity and the quality of the tracks are analyzed. Lower values of laser power and higher powder feed rate results in discontinuous deposition, while higher laser power and lower powder feed rate results in cracked deposits. Porosity is observed to vary from 6–45 % at different process conditions. Analysis of Variance (ANOVA) of deposition rate and track geometry is performed to estimate the major contributing process parameters. This study paves a way to understand effect of process parameters on LAM-DED for fabricating bimetallic joints and graded structures of Copper and SS304L.

Predicting Part-Level Thermal History in Metal Additive Manufacturing Using Graph Theory: Experimental Validation With Directed Energy Deposition of Titanium Alloy Parts

2019 ◽  
Author(s):  
Reza Yavari ◽  
Jordan Severson ◽  
Aniruddha Gaikwad ◽  
Kevin Cole ◽  
Prahalad Rao
Keyword(s):  
Heat Flux ◽  
Titanium Alloy ◽  
Additive Manufacturing ◽  
Energy Deposition ◽  
Process Conditions ◽  
Theoretic Approach ◽  
Temperature Trends ◽  
Directed Energy Deposition ◽  
Directed Energy ◽  
Metal Additive

Abstract The objective of this paper is to experimentally validate the graph-based approach that was advanced in our previous work for predicting the heat flux in metal additive manufactured parts. We realize this objective in the specific context of the directed energy deposition (DED) additive manufacturing process. Accordingly, titanium alloy (Ti6Al4V) test parts (cubes) measuring 12.7 mm × 12.7 mm × 12.7 mm were deposited using an Optomec hybrid DED system at the University of Nebraska-Lincoln (UNL). A total of six test parts were manufactured under varying process settings of laser power, material flow rate, layer thickness, scan velocity, and dwell time between layers. During the build, the temperature profiles for these test parts were acquired using a single thermocouple affixed to the substrate (also Ti6Al4V). The graph-based approach was tailored to mimic the experimental DED process conditions. The results indicate that the temperature trends predicted from the graph theoretic approach closely match the experimental data; the mean absolute percentage error between the experimental and predicted temperature trends were in the range of 6% ∼ 15%. This work thus lays the foundation for predicting distortion and the microstructure evolved in metal additive manufactured parts as a function of the heat flux. In our forthcoming research we will focus on validating the model in the context of the laser powder bed fusion process.

Characterization of Co-Cr-Mo Alloys Manufacturing via Directed Energy Deposition

2021 ◽  
Author(s):  
Michael Liu ◽  
Mathew Kuttolamadom
Keyword(s):  
Process Parameters ◽  
Energy Deposition ◽  
Process Conditions ◽  
Directed Energy Deposition ◽  
Metal On Metal ◽  
Knee Replacements ◽  
Scale Characterization ◽  
Directed Energy ◽  
Traditional Processing

Abstract In this study, Co-Cr-Mo samples that were fabricated via directed energy deposition (DED) at various laser powers and powder feed rates were characterized to ascertain their microstructure and mechanical properties. Co-Cr-Mo is a common alloy for total hip and knee replacements, dental, and support structures due to its biocompatibility, hardness and abrasion resistance, making them a preferred alloy for metal-on-metal (MOM) contact. This study was undertaken to understand the pertinent process parameters that would generate structurally viable bulk structures. High-resolution microscopy and spectroscopy revealed the presence of networked and jagged carbides with varying amounts of Mo. Further, XRD confirmed the presence of the γ and ε phases. Micro- and nano-scale characterization of the alloy fabricated at different process conditions showed material properties in line with those made via traditional processing approaches such as casting. Altogether, this investigation provided an understanding of the effect of additive manufacturing process parameters on the microstructure and properties of Co-Cr-Mo.

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