This paper advances the findings of the selective laser melting (SLM) of tool steel and stainless steel powders. The distinguishing feature is the melting of single layers in deep powder beds by a continuous CO_2 laser. First, effect of process parameters on the surface roughness for each material is investigated. Based on these results combined with visual observation of the solidified tracks, the question is then discussed as how the processability of various type of steels is changed. The results show that surface morphology of layers is affected strongly by scan spacing, thereby giving a lower average roughness at reduced scan spacing. The effect of scan speed is also remarkable. In addition, other roughness parameters such as the peak height and skewness are found to be useful tools for evaluation of laser melted surfaces.
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