This study is aimed to investigate the effect of adding on the three-dimensional printing (3DP) processed 420 stainless steel (SS). The final density, dimensional changes, and mechanical properties have been studied for the samples prepared under a series of sintering conditions. The contents of powder ranging between and and the sintering temperature were varied in the experiments in order to understand the dependence of densification kinetics and changes in properties on these process parameters. The experiments provide the evidence that the addition of can improve the densification kinetics of 420 SS significantly. The 420 SS samples produced by 3DP with sintered at for 6 h yielded 95% relative density, 190 GPa Young’s modulus, and 500 Knoop microhardness without any major sample shape distortion. The results are promising in that the 3DP process can be used to yield the prototype almost equivalent to a real part with a full mechanical capacity.