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Abstract: The γ’ precipitate coarsening kinetics in additively manufactured Ni-based superalloys needs to be investigated to predict the microstructure stability at high temperature. Therefore, we investigate the γ’ precipitate coarsening

kinetics in a laser powder bed fusion IN738LC Ni-based superalloy at 900 ◦C. We find that the initial bimodal γ’ precipitate size distribution at 24 h of ageing time changes to unimodal distribution at 168 h of ageing time at 900 ◦C. We perform the mean-field modelling to understand the transition physics using γ-γ’ composition and γ’ volume fraction obtained using atom probe tomography and find that the modelling results are consistent with the experimental observation. Based on the modelling, we found that the γ’ volume fraction is an important parameter in the mean-field modelling, which is slightly higher than the equilibrium value due to the nonequilibrium composition of γ-γ’ phases in the additively manufactured superalloy. Furthermore, the γ/γ’ interfacial energy is predicted to increase from bimodal to unimodal distribution due to an increase in Ti/Al ratio in γ’ precipitate, which increases the γ’ precipitate coarsening kinetics. It is also found that the γ/γ’ interfacial energy and z factor have more influence on the γ’ precipitate coarsening kinetics than the mobility parameter in additively manufactured IN738LC. In conclusion, the γ’ precipitate coarsening kinetics in additively manufactured Ni-based superalloy is predicted to be slightly faster than the alloy with equilibrium composition of phases.