Influence of the processing parameters on the final properties of powder-bed laser additively oxide dispersion strengthened (ODS) Fe-14Cr steel parts

Oxide Dispersion Strengthened (ODS) ferritic steels typically contain a fine dispersion of nanosized Y-Ti-O precipitates, leading to an improvement of creep properties and neutron swelling resistance. These alloys are usually manufactured by different successive steps: mechanical alloying, outgassing, hot extrusion and cold working. Mechanical alloying aims at the dissolution of Y and Ti atoms into the ferritic matrix. This process leads to the precipitation and growth of fine Y-Ti-O oxide dispersoids during the heat treatments and the consolidation by hot isostatic pressing and/or by hot extrusion. Considering the limitations regarding the final shapes complexity of components obtained by this traditional fabrication route, the evaluation and development of alternative production methods are currently studied in order to increase the widespread use of ODS alloys. In the frame of assessing the potentialities of additive manufacturing to manufacture ODS complex parts, a Fe14Cr1W + 0.3percent Y2O3 + 0.3percent TiH2 milled powder is consolidated by Selective Laser Melting (SLM). The influence of processing parameters (scanning speed, scanning strategy, laser power, etc…) on the final microstructures as well as the final densities are studied. For this purpose, several microstructural techniques (scanning electron microscopy, electron backscattered diffraction & transmission electron microscopy) are coupled in order to analyze the cross-sections. First results are quite promising since density of more than 98percent could be achieved with a non-optimized powder. As expected, processing parameters strongly influence the microstructural evolution, especially the grains size and the precipitates’ density. The influence of powder properties, such as particles size distribution and flowability, on the final properties are also studied and presented in details. The objective of this work is to demonstrate how process parameters tailor the microstructure of such alloys and so final mechanical properties.