M300 Process Parameters Optimization for Direct Energy Deposition

Direct Energy Deposition has been employed to produce M300 samples in two optical configurations. Process parameters effects on the quality of the printed parts have been studied, analysing the relashionship with the microstructure. The same samples have been produced in both free atmosphere and inert chamber . Primary cellular arm spacing has been computed also for the evaluation of the cooling rate at different height of the specimens. It has been found that the two atmosphere show opposite trends. In free atmosphere the PCAS increases from 8um to 13.5um. Using the airtight room insted it decreases from 6um to 4um for the different cooling rates. The reason of that can be explained by the presence of Argon that in the considered temperature range has a convective heat transfer coefficient 5 times bigger than the air. For the quality definition, the porosity, the meltpool shape and the geometrical accuracy has been studied. They are function of the re-melting during the process. Again the Ar atmosphere plays an important role for a consistent increase of the working temperature. The meltpools in the inert chamber are bigger, hence become more difficult the control of the shrinkage. The parameter selection has been directed also to the minization of the austenite content, that is the most undesirable effect in this kind of steels. For this reason the phases present in the microstructure has been also studied performing both the XRD and EBSD analysis.