Introduction to the SLM process
Selective laser melting (SLM) is one of the new additive manufacturing techniques that emerged in the late 1980s and 1990s. During the SLM process, a product is formed by selectively melting successive layers of powder by the interaction of a laser beam. Upon irradiation, the powder material is heated and, if sufficient power is applied, melts and forms a liquid pool. Afterwards, the molten pool solidifies and cools down quickly, and the consolidated material starts to form the product. After the cross-section of a layer is scanned, the building platform is lowered by an amount equal to the layer thickness and a new layer of powder is deposited. This process is repeated until the product is completed.
This layer-by-layer process was first used to produce prototypes, but the trend is towards direct manufacture of components because of its ability to net-shape manufacture complex structures from a CAD model and a wide range of materials without the need of expensive tooling and machining so that the delay between design and manufacture is minimised. Another advantage is that the powder is melted only locally by the laser and the rest of the powder can be recycled for further fabrication. So far, here in AMPLab at the University of Birmingham, SLM has been used to selectively melt Ni-based superalloys, Ti-based alloys, Al-based alloys and Nb-based alloys to fabricate components and structures for automobile and aeropsace applications.
SAMULET 3.4 project details
| Full title |
SAMULET 3.4 |
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| Description |
SAMULET 3.4 was a TSB funded project to identify the optimum processing parameters and support structures for fabrication of T700 Vanes using SLM. The project involved investigating the influence of laser processing parameters and laser scanning strategy on the microstructure and structural integrity (such as porosity) of as-fabricated Ti-6Al-4V alloy samples and the study of the influence of post-build heat treatment and hot isostatic pressing on structural integrity, microstructure and mechanical properties such as tensile, low cycle fatigue, crack propagation properties and fracture behaviour. Support structures were designed to withstand enormous stress buildup during SLM and to ensure successful fabrication of T700 vanes. Surface roughness measurement, distortion measurement by GoM laser scanning and residual stress measurement using synchrotron X-ray diffraction were also be carried out.
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| Key partners |
TSB and Rolls-Royce plc |
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| Total budget |
£250, 000 |
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| Team members |
Moataz.M.Attallah, Nick.Adkins, Chunlei Qiu
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Additive manufacturing of aluminium alloys and nickel superalloys project details
| Full title |
Additive manufacturing of aluminium alloys and nickel superalloys |
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| Description |
This project was funded by Microturbo for the research and investigation into the usage of high temperature Al alloys and Ni-based superalloys in the manufacture of components using SLM. The effect of processing parameters and scanning speed on porosity, the amount of cracks, and mechanical properties were investigated, and tomography was used for characterisation of the shapes, as well as macro distribution of cracks and porosity in the laser fabricated components. In addition, tensile and creep tests, distortion measurement by laser scanning and comparison of surface treatments for SLM fabricated materials were carried out.
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| Key partners |
Microturbo |
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| Total budget |
£200, 000 |
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| Team members |
Moataz.M.Attallah, Noriko Read, Wei Wang and Xiqian Wang
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