Laser-based metal deposition process such as selective laser melting (SLM) is one of Direct Metal Deposition (DMD) or Additive Manufacturing (AM) processes. Due to the nature of its layer-by-layer process, the microstructures from the bottom layers to the top layers are significantly different due to highly thermal gradient induced by laser beam combined with different cooling rates at each built layer. The SLM process parameters such as laser power, scan speed, layer thickness, hatch spacing etc have a major influence on the mechanical properties of the material fabricated. The relationship between mechanical properties associated with microstructure and process parameters is critical for the manufacture of functional components. The understanding of this relationship will help to facilitate future studies on manufacture and repair of titanium alloy parts/components with SLM technology. Increase in layer thickness will lead to increase in productivity. However, such an increase may impact on the mechanical properties of the material.

This paper presents the effect of powder layer thickness on the mechanical properties (tensile and fatigue) of manufactured specimens. The experimental results in this investigation showed that the increase in layer thickness from 30 to 90 µm did not affect the tensile strengths but the ductility was dramatically reduced. The fatigue life was also significantly decreased. The results indicate that the SLM process needs to be optimised for a thicker powder layer case.

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