**4. Conclusions**

This work investigated the e ffective thermal di ffusivity of laser-deposited AISI H13 tool steel, and the following conclusions were drawn:

(1) The e ffective thermal di ffusivity of the laser-deposited AISI H13 tool steel is lower than that of the reference value of the cast material, which is critical for applications where the heat transfer is a key parameter.

(2) Despite the directional nature of the DED process, the resulting thermal properties presented no anisotropy and heat was conducted equally in all directions.

(3) Various cross-sections of the laser-deposited AISI H13 tool steel were studied and no porosity was found. Therefore, the thermal di ffusivity reduction could not be attributed to the existence of internal voids. The reduction of the e ffective thermal di ffusivity was due to the microstructure that developed during the fast cooling of the deposited material, in which the fine grain size reduced the heat transfer through the material.

(4) The microstructure that developed within the deposited material was directly related to the cooling rate, which was higher at the beginning of the DED process. This is why the e ffective thermal di ffusivity of Sample 1 (situated at 0–2 mm from the interface) was lower than that of Sample 2 (at 4–6 mm from the interface).

(5) The e ffect of the DED process on the substrate was minimal and did not a ffect the thermal di ffusivity of the base material.

(6) If the e ffective thermal conductivity is not considered the cooling capability of the DED-manufactured tools is overestimated.

This work extends current knowledge on the thermal properties of DED materials, and the thermal di ffusivity and conductivity di fferences encountered may also a ffect other AM processes. Therefore, further research is necessary to fully characterize AM parts.

**Author Contributions:** Conceptualization, J.I.A. and M.C.; investigation, M.C., A.S. and A.M.; software, J.I.A.; writing—original draft preparation, J.I.A., M.C. and A.L.; supervision, A.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors gratefully acknowledge the financial support for this study from the European Union, through the H2020-FoF13-2016 PARADDISE project (contract number 723440) and from the Ministry of Economy and Competitiveness (grant number DPI2016-77719-R).

**Conflicts of Interest:** The authors declare no conflict of interest.
