Effect of building strategy on sample dimensions and properties in direct laser deposition of Ti-6Al-4V

Laser additive manufacturing (LAM) techniques have evolved significantly in recent years. They have the potential advantage of complex geometry and manufacturing speed compared to conventional manufacturing processes. Direct laser deposition (DLD) is a form of LAM process where a moving laser power source creates a melt-pool, into which a powder is injected to build a desired shape. In this study, building strategy was investigated to understand its effect on geometrical tolerance and defect induced porosity when using DLD. It involves a combination of skin and core. The build order, powder flow rate, direction and number of layers of the skin was varied whilst keeping all the parameters for the core constant. The results show that it is beneficial to build the skin separate from the core. Increasing the powder flow rate when manufacturing the skin improves both the geometrical tolerance and porosity of the sample. There is potential improvement in geometrical tolerance when two layers are used for the skin but care must be taken as large lack-of-fusion type defects can be introduced.