Investigation on the inclusions in maraging steel produced by Selective Laser Melting

Maraging steel is an iron-nickel steel alloy which achieves its superior strength, hardness and toughness by aging the martensite phase.In earlier investigations, however, the toughness of selective laser melted (SLM) and subsequent aged maraging steel was found to be low.Several authors attribute this to the large oxides present in the finished product.In this work, the origin for these oxides is investigated by using microscopy and spectroscopy.The analysis is done on specimens produced under different processing conditions and the most important characteristics of the inclusions are discussed.It is found that during the SLM process, an oxide layer containing Al and Ti is created on top of each layer.Upon melting the next layer, the oxide layer is broken and dragged further.Therefore, accumulations of oxide material are found in the final product as large, irregularly shaped inclusions.