Selective laser melting of TiB2/H13 steel nanocomposites: Influence of hot isostatic pressing post-treatment

A TiB2/H13 steel nanocomposite powder was produced by high-energy ball milling and used to fabricate components by selective laser melting (SLM), an additive manufacturing process. Hot isostatic pressing (HIP) post-treatment was applied to improve the final density of the SLM-fabricated component, and the results were compared with those of an untreated component. The microstructure of the as built nanocomposite comprised of fine equiaxed grains with TiB2 particles homogenously dispersed in the H13 steel grains and grain boundaries. Relative to the unreinforced base metal, the hardness of the SLM-processed nanocomposite was found to be slightly higher, but friction and wear rate significantly decreased. The HIP post-treatment effectively eliminated major pores in the nanocomposites. In addition, the post-treatment transformed the continuous grains into intermittent grains with crystalline clusters. A further increase in the average hardness values with large standard deviations was observed after HIP treatment because of the competition between the high-temperature annealing effect and the improvement in density. A slight increase in the wear rate after the post-treatment was observed as a result of the grain coarsening and agglomeration of the TiB2 nanoparticles in the H13 matrix. (C) 2017 Elsevier B.V. All rights reserved.