Speaker
Description
Additive manufacturing (AM) is a material-processing technique that is expanding rapidly, with applications in various fields such as repair technology under thin or thick deposits, or the development of complex shaped parts.
In this work, AISI HSS M4 thick deposits of various geometries (thin walls, bulk specimens, and large plate samples) are obtained from a Laser Metal Deposition (LMD) process using a medium alloy steel as the substrate. Such geometries allow to highlight the influence of heat accumulation during LMD processing on both the solidification structure and the subsequent solid state transformations that set the macrostructure and the microstructure respectively, those features being known to strongly influence the final mechanical properties.
It is well established that higher thermal gradients are achieved during AM processes, together with complex thermal histories within the building deposit. Even the characterization of the final microstructure in the as-built specimen is not enough to understand how the microstructure evolves during AM processing. Therefore, the use of validated thermal models that can restore the actual thermal histories for any location within the deposit can be very helpful.
In this study, a validated thermal model has been used to set the thermal histories of defined positions within the deposits of various geometries. Restored thermal histories are then used to determine peak temperatures and thermal gradients that influence both the solidification structure and the solid state transformations, the latter phenomena being also highlighted under dilatometry tests that have been performed. Hardness measurements performed at various scales, and microstructural characterization under SEM/EDX/EBSD have been carried out, thus leading to the identification of phases that are present in the as-built samples.
It is found that the hardness in the deposits varies according to the local thermal history that also influences the microstructure, including the nature, the size and the location of carbides. Regarding the matrix within the cells or grains, its nature is enhanced through dilatometry tests performed under different heating/cooling rates, while highlighting at the same time the diffusive or displacive mechanisms of the related solid state transformations.
The influence of both hardness and microstructure on mechanical properties and wear behavior are also discussed.
Summary
Additive manufacturing (AM) is a material-processing technique that is expanding rapidly, with applications in various fields such as repair technology under thin or thick deposits, or the development of complex shaped parts.
In this work, AISI HSS M4 thick deposits of various geometries (thin walls, bulk specimens, and large plate samples) are obtained from a Laser Metal Deposition (LMD) process using a medium alloy steel as the substrate. Such geometries allow to highlight the influence of heat accumulation during LMD processing on both the solidification structure and the subsequent solid state transformations that set the macrostructure and the microstructure respectively, those features being known to strongly influence the final mechanical properties.
It is well established that higher thermal gradients are achieved during AM processes, together with complex thermal histories within the building deposit. Even the characterization of the final microstructure in the as-built specimen is not enough to understand how the microstructure evolves during AM processing. Therefore, the use of validated thermal models that can restore the actual thermal histories for any location within the deposit can be very helpful.
In this study, a validated thermal model has been used to set the thermal histories of defined positions within the deposits of various geometries. Restored thermal histories are then used to determine peak temperatures and thermal gradients that influence both the solidification structure and the solid state transformations, the latter phenomena being also highlighted under dilatometry tests that have been performed. Hardness measurements performed at various scales, and microstructural characterization under SEM/EDX/EBSD have been carried out, thus leading to the identification of phases that are present in the as-built samples.
It is found that the hardness in the deposits varies according to the local thermal history that also influences the microstructure, including the nature, the size and the location of carbides. Regarding the matrix within the cells or grains, its nature is enhanced through dilatometry tests performed under different heating/cooling rates, while highlighting at the same time the diffusive or displacive mechanisms of the related solid state transformations.
The influence of both hardness and microstructure on mechanical properties and wear behavior are also discussed.
| Speaker Country | Belgium |
|---|