Title: Effect of heat treatment on the microstructures and hardness of selective laser melted Rene88DT superalloy

Authors: Jian Liu; Yu Yan; Qin Peng; Yu Lei

Addresses: Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China; Key Laboratory for Advanced Materials Processing, Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China ' Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China; Key Laboratory for Advanced Materials Processing, Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China ' Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China; Key Laboratory for Advanced Materials Processing, Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China ' Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China; Key Laboratory for Advanced Materials Processing, Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China

Abstract: Selective laser melted Rene88DT specimens with columnar grains (specimen C) and near-equiaxed grains (specimen E) were fabricated, on which solution-aging and direct aging treatments were applied, respectively. The evolution of microstructures and hardness of both specimens was investigated. Results show that specimen C showed columnar grains with aspect ratio of 3.6 and 5% difference in hardness between vertical and horizontal directions, while specimen E with near-equiaxed grains (aspect ratio of 1-2) was isotropic. The as-deposited alloys consisted of γ-matrix, carbides and Laves phases. After solution-aging treatment, equiaxed grains (56 μm) with annealing twins, blocky μ phases (1 μm) and dispersively distributed γ′ (40 nm) were observed in specimen C. After direct aging treatment, rod-like γ′ phases with 40 nm in length and 15 nm in diameter were precipitated in specimen E. Specimen E showed higher hardness than specimen C because of stronger grain boundary strengthening, substructure strengthening and second-phase strengthening.

Keywords: selective laser melting; Rene88DT superalloy; heat treatment; microstructures; hardness.

DOI: 10.1504/IJCMSSE.2020.10034959

International Journal of Computational Materials Science and Surface Engineering, 2020 Vol.9 No.4, pp.304 - 317

Received: 08 Jun 2020
Accepted: 18 Aug 2020

Published online: 18 Jan 2021 *

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