Networked γ′ in additively manufactured cobalt-based superalloy through dislocation cell-templated precipitation

The cobalt-based γ′-strengthened superalloy shows great promise across various sectors, including power generation and aerospace. Laser Powder Bed Fusion (LPBF) technology is well-suited to meet the requirements for superalloys with strong textures or single-crystal microstructures. However, post-processing often leads to recrystallization, altering the desired microstructure. In this study, we propose the Dislocation Cell-templated Precipitation (DCP) method, which utilizes the elemental segregation at the high-density dislocation cell walls inherent in LPBF to control three-dimensional morphological evolution of γ′ phases. This process results in a unique networked γ′ structure in a newly developed cobalt-based superalloy (49Co-30Ni-10Al-5V-4Ta-2Ti at. %), which is distinctly different from the conventional cubic γ′ phase morphology observed in cast samples. Compared with the conventional cubic γ′ morphology in cast alloys, the networked γ′ structure exhibits significantly enhanced strength at both room and elevated temperatures. Furthermore, the networked γ′ structure shows excellent thermal stability, retaining its morphology and columnar grains after 120 h at 1000 °C, without forming detrimental phases. These findings offer new insights into the microstructural engineering of LPBF-manufactured superalloys. Dislocation Cell-templated Precipitation (DCP), employed during the Laser Powder Bed Fusion process, leverages high-density dislocation cells and elemental segregation to control γ' phase precipitation and promote the formation of an unconventional network-like γ' structure. The networked γ′ architecture exhibits superior thermal stability and mechanical strength, offering a promising approach for advancing additively manufactured superalloys.