Statistical analysis of the effect of processing conditions on powder catchment efficiency in the Direct Laser Deposition (DLD) process

Metallic powders are used in direct laser deposition (DLD) processes to build three-dimensional objects directly from a computer aided design (CAD) model. The low powder deposition efficiency (below 40%) has been a concern for the industries using the techniques, although undamaged powders can be recycled in some applications. However, for aerospace industries, re-use of powders may not be desirable because of the very high part quality required. In addition, poor efficiency increases the proportion of misdirected, semi-molten powders, which adhere to the surface adversely affecting the surface finish. In this investigation, design of experiments and statistical modeling techniques were used to understand and identify the most influential parameters affecting the deposition efficiency in this multiple variable process. Experiments were conducted to simultaneously study the effect of 9 DLD process parameters. Using a 1.5 kW diode laser to deposit 316 L steel powder the maximum powder usage efficiency was found to be limited to 60%. After identifying the most influential factors and trends, further tests were then carried out and the deposition efficiency was raised to 75%. The work identifies the significant deposition parameters and shows the importance of targeting them.