Evaluation under near-equilibrium conditions of the powders mixture AISI S2 Tool Steel and Silicon Carbide for Laser Powder Bed Fusion applications

Forecast the microstructures obtainable in alloys printed through Laser Powder Bed Fusion (LPBF) is a challenge in Additive Manufacturing (AM). The out-of-equilibrium condition of the solidification during the printing increases the difficulty to predict the final microstructure. Techniques such as thermal analysis in near-equilibrium conditions can be adopted to overcome the challenge. With thermal analysis, it is also possible to evaluate the influence of the elements of the alloy on the microstructure.
The main aim of this research is to fabricate an innovative alloy with good wear and tribological properties, in particular, an alloy with self-lubricating properties provided by the presence of graphite into the final microstructure. In this work, the evaluation of AISI S2 tool steel + silicon carbide (SiC) is performed in term of microstructural characterization after a Differential Thermal Analysis (DTA) at 5 and 20°C/min of cooling rates. 5, 10, 15 and 20% in volume of SiC were added to S2 tool steel. The influence of SiC on the final microstructure was investigated through optical and scanning electron microscopy with EDS and EBSD analysis that allow the evaluation and comparison of the different phases of the microstructures. The amount of SiC influence the final microstructure, passing from a fully pearlitic matrix, for the lowest amount, to a fully ferritic matrix with Iron/Molybdenum eutectic carbides and precipitates, and several types of graphite increasing the SiC amount