Gas atomized (GA) and water atomized (WA) 1(418 superalloy powders were injection molded, and a detail comparative investigation on microstructure and mechanical properties of MIM418 superalloys was carried out. The GA sample possesses higher sintering density than the WA sample due to its lower oxygen content, narrow pore size distribution and higher packing density. Both superalloys achieve near full dense after HIPing, and increasing HIPing temperature leads to grain growth and leaving carbide particles at the site of the original prior particle boundaries (PPBs) within the new grains. The GA powder leads to finer and more homogeneous gamma' precipitates and carbides, as well as equiaxed grains (31 mu m), while the WA powder results in larger gamma' precipitates with higher coarsening rate, higher concentration of PPBs, and smaller grain size (26 mu m). The GA sample exhibits satisfactory levels of tensile strength (1425 MPa) and yield strength (1004 MPa) combined with a significantly improved elongation (19.4%), which is suitable for high performance applications. The WA sample has comparable mechanical properties with that of the cast K418 superalloy, which can be used for less critical and low cost demand applications. (C) 2015 Elsevier B.V. All rights reserved.