Characterization of the process control for the direct laser metallic powder deposition

Direct Laser Metallic Powder Deposition Process is one of the most popular direct additive manufacturing processes which use laser as a heat source to deposit the metallic powder layer by layer for surface modification and fabrication of three-dimensional parts. The properties of the deposited layer, such as microstructure, hardness and dimensional accuracy determine the usage properties of the processed parts. The temperature and size of the melt pool, the cooling rate and the solidification conditions dominate the microstructure, hardness and dimensional accuracy. In this work, a closed-loop process control based on the infrared (IR)-temperature signal was investigated by deposition of thin walls. Process control with constant set-values and path-dependent set-values was tried and compared. The results showed that the process control with a path-dependent set-value can notably improve the homogeneity of the microstructure and hardness as well as the dimensional accuracy of the deposited samples.