High-density tungsten fabricated by selective laser melting: Densification, microstructure, mechanical and thermal performance.

• Selective laser melting tungsten with a relative density of 98.71% was obtained firstly. • Coarse columnar grains changed to fine grains with increasing laser scan speed. • Compressive strength and thermal conductivity were 1523 MPa and 148 W/mK. High-density pure tungsten (W) fabricated by selective laser melting (SLM) has been considered as a substantial challenge due to its high melting point of 3410 °C. In this study, near fully dense W samples with a relative density of 98.71% were obtained for the first time through a series of optimization experiments during the SLM process. The characteristics of the surface and the formation mechanism of the micro defects were systematically elucidated. Additionally, it was found that the typical microstructures of horizontal and vertical planes experienced successive changes, where coarser columnar grains changed to uniform finer grains when increasing the laser scan speed from 50 mm/s to 400 mm/s. The compressive strength, micro hardness and thermal conductivity of the optimal SLM sample was improved to 1523 MPa, 428 HV 3 and 148 W/m·K, which were superior to the sample produced by the conventional methods. The relationship of processing parameters to the surface morphology and microstructure evolution and material properties associated with fusion reactors was established in order to optimize the performance of SLM pure W and explore the possibility of further application in fusion reactors. [ABSTRACT FROM AUTHOR]