A simulation method with the embedded atom model (EAM)/alloy potential energy function was used to determine the mechanical characteristics of nanoscale spherical solid and hollow iron (Fe) particles of various sizes under different laser heating rates during laser powder bed fusion (PBF) additive manufacturing (AM). We concluded that the coalescence temperatures of nanoscale spherical solid and hollow Fe particles were in the range from 1300 to 1732 K and from 1150 to 1682 K, respectively. We found that the macroscopic melting point of Fe (1811 K) was much greater than the melting temperatures of nanoscale spherical solid and hollow Fe particles. We also found that the melting temperatures of nanoscale spherical solid and hollow Fe particles were in the ranges from 1600 to 1785 K and from 1515 to 1767 K, respectively. We found that the interdiffusion of Fe atoms slows down while the heating rate increases. The solid-state sintering of nanoscale spherical solid and hollow Fe particles can readily take place at room temperature (300 K). We found that the interdiffusion of Fe atoms slows down while the heating rate increases. The solid-state sintering of nanoscale spherical solid and hollow Fe particles can also spontaneously occur at room temperature (300 K). The sizes and geometrical microstructures of nanoscale particles and laser heating rates are important factors during laser PBF AM.