Microstructural Characteristics and Mechanical Properties of an Additively Manufactured Nickel-Based Superalloy

Abstract

The nickel-based superalloys processed by additive manufacturing are very promising structural materials in aircraft engines as high-pressure turbine discs. In this work, a nickel-based superalloy with good mechanical performance and few defects was manufactured by optimized selective laser melting (SLM) processing. We then investigated the influences of post heat treatments on its microstructural characteristics and mechanical performance. The results indicated that a fine grain size with uniform grain orientation was presented in the as-printed nickel-based superalloy sample. After heat treatments, the grains were slightly grown and grain orientation was also changed. Under transmission electron microscopy, fine subgrains with an approximate size of 0.5 μm were found in the as-printed sample which accompanied massive dislocations and discontinuous Laves phases. After the post heat treatments, fine subgrains and less dislocations were retained. On the other hand, massive γ′ and γ″ precipitates with an orientation relationship of (001)[100]γ′//(100)[001]γ or (001)[100]γ″//(100)[001]γ were formed. As a result, the yield stress and tensile strength increased to 1362 and 1410 MPa, respectively, in a heat-treated sample, which retained the identical elongation of the as-printed specimen.

Keywords

• additive manufacturing
• nickel-based superalloy
• solution and aging treatment
• dislocations
• precipitates
• tensile properties