, Meir Kreitman, ,
Laser based additive manufacturing of metals relies on many micro-sized welds to build a part. A simplified, well studied case of this process is a single scan of the laser across a single layer of powder. However, there is a lack of mechanical property measurements of the tracks produced in such experiments. Nanoindentation measurements on laser track cross-sections of nickel super alloy 625 reveal hardness differences between the track melt pool and base material as well as variations with laser scan speed. There is a change from ≈5.5 GPa in the track melt pool to ≈4.8 GPa in the base material for laser settings of 195 W and 800 mm s−1. In comparison, the increase in hardness in the melt pool is not observed for settings of 195 W and 200 mm s−1. It is believed that the difference in thermal histories supported by thermographic measurements causes a difference in the dislocation density in the melt pool. This results in a difference in hardness between the two tracks. The effects of the local crystal orientation, dendritic spacing, and residual stress are considered in the interpretation of results.
TMS 2019 Conference Proceedings
March 10-14, 2019
San Antonio, TX
additive manufacturing, hardness, residual stress, microstructure, electron backscatter diffraction