Process variation in Selective Laser Melting of Ti-6Al-4V alloy

The present work explores the variation in Ti-6Al-4V part quality introduced by the key process operations of Selective Laser Melting (SLM) process, the recoating, the gas flow, and the laser beam irradiation. Novel specimens and experiments were designed to characterize the differences in surface quality and thermal history as a function of part geometry and location on the build platform. The variation in the roughness of inclined surfaces shows a clear dependency on the laser incidence angle and the influence of gas flow on process by-products. The direction in which the laser beam traverse across the build area with respect to the gas flow direction also affects the surface quality. Thermal profiles were recorded by attaching thermocouples to the surface of the built part with various geometries. The measured temperature profiles show intense local fluctuations due to the rapid movement of the laser beam. The parts also experience a continuous heat treatment throughout the SLM process due to the low effective conductivity of the powder bed and continuous heat input by the laser