**1. Introduction**

SKD61 and H13 are types of hot work tool steels applied to casting molds, extrusion tools, forging dies, etc., and the hardness of SKD61 (229 BHN) is lower than that of H13 (235 BHN) [1]. Both steels are fabricated by conventional methods requiring expensive dedicated tools, and thus are inappropriate for small-scale or complex-shape productions [2–4]. Selective laser melting (SLM), is a laser powder-bed additive manufacturing process that is suitable for the processing of tool steels, including SKD61 and H13, because it offers the ability to not only reduce the amount of machining and hence wastage of this expensive material, but also to produce intricate molds with a nearly full density and a refined microstructure [3,4].

The mechanical behavior of hot work tool steels prepared by the PBF method is one of the most important characteristics [5,6]. It was reported that the hardness of PBF SKD61 fabricated from commercial powders was higher than that made from gas atomized spherical powders [4,7]. Very recently, a few studies have addressed the mechanical properties of tool steel processed by PBF using nanoindentation [3,8]. For example, the H13 PBF-processed at 200 mm/s scan speed exhibited the lowest creep resistance and highest hardness values. However, very few studies have dealt with the mechanical behavior of PBF SKD61 using nanoindentation. It is thus necessary to perform nanoindentation tests to probe the creep behavior of the PBF SKD61 and compare it with that of PBF H13 [9,10].

In a previous study, PBF processing at an 800 mm/s laser scan speed was applied successfully for SKD61 powders [4,11]. This study expands on those reported findings by using nanoindentation tests to investigate the mechanical properties of PBF SKD61. Results for PBF-processed H13 at the same laser scan speed sourced from the literature are used in the evaluation conducted here [2].
