Process optimization of melt growth alumina/aluminum titanate composites directed energy deposition: Effects of scanning speed

Abstract In-envelope hybrid manufacturing systems comprised of directed energy deposition (DED) and machining provide flexibility for the fabrication of complex geometries with minimal setup changes. However, for these manufacturing set ups, the effects of deposition parameters such as laser power and scanning speed on the quality of the build remain relatively unexplored. An important aspect for developing components with reliable mechanical properties is a thorough understanding of DED thermodynamics during fabrication. Therefore, DED thermodynamics were defined based on the strengthening properties derived from the thermal gradient (G) and solidification rate (R) of the melt pool. Other factors influencing DED thermodynamics include substrate geometry and surface finish which are expected to affect cooling rates and adhesion, respectively. In this work, stainless steel 316L specimens were fabricated varying laser power intensity, scanning speed, and deposition substrate. The effect of these parameters on the microstructure of the sample components were analyzed. Microstructural evolution at various points within and between layers was studied and correlated to localized hardness. An increase in mechanical properties for fine, equiaxed grains demonstrates the Hall-Petch principle for strengthening of components.

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

Volume 1: Additive Manufacturing; Advanced Materials Manufacturing; Biomanufacturing; Life Cycle Engineering; Manufacturing Equipment and Automation ◽

10.1115/msec2020-8389 ◽

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.

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