Effect of structural support on microstructure of nickel base superalloy fabricated by laser-powder bed fusion additive manufacturing

Multi-laser scan strategies for enhancing creep performance in LPBF

“…At the time of writing, it is not possible for critical components to be manufactured using LPBF alloy 718 as there is a lack of research and understanding about the effect of the LPBF-specific microstructure on its mechanical performance, particularly for high temperature applications where creep may be an issue. Furthermore, due to the fine cellular dendritic microstructure produced by the LPBF process for as-built (AB) material [7], regardless of the use of supports, which can act as heat sink/source [8], the mechanical performance of materials/components, such as ductility, has been found to be inferior to that of cast and wrought materials, especially for creep [9]. Although the creep performance of LPBF alloy 718 has been studied previously, the tests performed were of too short durations for creep mechanisms, such as microvoid coalescence, to have fully taken place (sometimes, less than 2h) [9].…”

Powder bed fusion additive manufacturing of Ni-based superalloys: a review of the main microstructural constituents and characterization techniques

“…The expected lack of Laves formation is further supported by simple cooling experiments on IN718 which seem to indicate that Laves formation should be suppressed at cooling rates experienced during L-PBF [222]. However, based on several reports in AM literature, it becomes clear that non-equilibrium formation of Laves does occur [50,98,99,191,209,223]. This may be due to the repeated melting that occurs from the layer-by-layer process within L-PBF, and the high level of Nb microsegregation.…”

“…a, b, c, d, e and f adapted from [102], g from [191], and h from [159] with permission. [98,116,171,191,192]. It has also been found that fewer carbides form during L-PBF compared to E-PBF.…”

“…Figures 16bf and 15b use TEM-EDS in the identification of carbides and oxides within their IN718 and Haynes 282 alloys, respectively. Similarly, and not shown here, TEM-EDS has been used in the identification of TCP phases such as Laves in IN718 [98]. Lastly, analysis of the chemical composition at almost atomic scale can be done via TEM by an electron spectrometer that creates an energy-loss spectrum (i.e., EELS) [243].…”

“…3e). Based on the literature, the noted range of primary dendritic arm spacings (PDAS) is between 0.2 and 1.8 lm [98,99]. Most studies report no secondary dendrite arms due to the fast solidification rates.…”