Processability of different IN738LC powder batches by selective laser melting

Selective laser melting of high γ′ strengthened superalloys such as IN738LC is of huge interest for stationary gas turbine applications. In order to identify the influence of the powder characteristics on SLM processing, several batches of commercially available IN738LC powder made by gas and water atomization were characterized with respect to particle size distribution, morphology and chemical composition. The different powders were processed under equal conditions by selective laser melting (SLM) and the build quality was assessed by quantitative image analysis. Samples made out of the water atomized (WA) powder showed a higher porosity after SLM compared to the spherical gas atomized (GA) powders due to the greater irregular morphology of the powder. The porosity of the gas atomized powder batches was found to be influenced by the flow behavior of the powder. Large differences were observed for the hot cracking susceptibility of the different powder batches during SLM processing. The cracking density was correlated to the chemical composition and it was found that the minor element Si has a large influence on the SLM processability of the IN738LC powder. A strict control of this element is important to decrease the hot cracking tendency and extends the SLM processing window of this alloy.