Influence of Nd : YAG parameters on the selective laser sintering of metallic powders

Compared with CW CO2 laser sources, Nd:YAG lasers with Q-switching capability offer a wider parameter range, with improved sintering control, due to the short pulsed energy delivery. In particular, thermal diffusion being strictly limited by the nanosecond interaction between the energy pulse and the powder, higher accuracy can be achieved, while caking can be minimized. By systematically varying average power, scan velocity and repetition rate, process maps are established, for various materials, such as nickel and cobalt alloys, and titanium. Sintering depth and macrostructures are determined for different parameter sets. Basic models and physical explanations are given, for the various phenomena and consolidation processes. This mapping provides a correlation between the process parameters and the structure and properties of the produced parts. Results show that roughness and density are related to the pulsed energy delivery. For example, it is shown that multi-layer Ti samples can be sintered to a density close to 80 %.