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Research Papers

A Numerical Investigation into Residual Stress Characteristics in Laser Deposited Multiple Layer Waspaloy Parts

[+] Author and Article Information
A. M. Kamara1

Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering,  University of Manchester, M13 9PL, United Kingdoma.kamara@manchester.ac.uk

S. Marimuthu, L. Li

Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering,  University of Manchester, M13 9PL, United Kingdom

1

Corresponding author.

J. Manuf. Sci. Eng 133(3), 031013 (Jun 15, 2011) (9 pages) doi:10.1115/1.4003833 History: Received July 21, 2010; Revised March 10, 2011; Published June 15, 2011; Online June 15, 2011

This paper reports an investigation into the residual stress generated with the laser direct metal deposition (LDMD) process and particularly that which arises from the deposition of a multiple-layer wall of Waspaloy on an Inconel 718 substrate. These Ni-based superalloys possess excellent strength and creep resistance at relatively high temperatures. These are attributes contributing to their extensive utilization in various applications in modern industry and particularly in the aerospace sector. Depending on its magnitude and nature (i.e., whether tensile or compressive), the residual stress generated in the combined use of these materials in an LDMD process affect interfacial bonding and structural integrity during the process, and it can also cause unpredicted in-service failures. Prediction of its distribution in the deposited structure is vital toward enhancing process optimization that could lead to its control. Using the ANSYS finite element package, this study investigated the residual stress characteristics in a 6 mm wide and 14 mm high Waspaloy wall that was built from the deposition of 20 layers each consisting of 6 parallel tracks. The predicted results were validated by published experimental data and showed very good agreement. The results indicated that irrespective of the position in the height of the wall, the stress along the length of the wall oscillates about a stress-free state. Along the height of the wall, the stress was found to vary with position. The wall is near stress-free close to the substrate, while, at positions close to the free surface, the stress was uniaxially tensile. The largely tensile stress in the beam scanning direction in the deposited wall increases with number of layers while the stress in the build-up direction in the wall is close to zero.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

The geometry and mesh used in the analysis

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Figure 2

Schematic illustration of the raster pattern of laser beam scanning used in the manufacture of the wall

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Figure 4

Contours plots of (a) z-component residual stress, σz , and (b) x-component residual stress, σx , as recorded through the x–z plane on the wall

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Figure 6

Residual stress (a) z-component, σz , and (b) x-component, σx , measured at positions in the direction of the x-axis and at the location 2 mm below the top surface of the wall

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Figure 7

Residual stress (a) z-component, σz , and (b) x-component, σx , measured at positions along the z-axis through the height of the wall

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Figure 8

Comparison of the x-component of residual stress, σx , for the wall builds of different number of deposited layers, measured in each case at positions along the z-axis through the height of the wall and the substrate

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Figure 9

Comparison of the distortion in the components with clad walls of the different number of deposited layers studied

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Figure 10

Schematic representation of stress generation: (a) initial stage with hot top layer, (b) the effective size of the top layer after cooling, (c) the deflection caused by the size mismatch, and (d) the direction of stress generation when the deformation shown in (c) is constrained [7]

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Figure 5

Residual stress (a) z-component, σz , and (b) x-component, σx , measured at positions in the direction of the of the x-axis and at the location 2 mm above the base of the wall

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Figure 3

Schematic illustration of beam/substrate interaction substrate at different times during beam scanning and length of clad, vdt, which is manufactured in every scan over a time of dt.

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