Comparisons of particle's thermal behavior between Fe-base alloy and boron carbide in plasma transferred-arc (PTA) space was made based on theoretical evaluation results in this article. It was found that most of the Fe base particles would be fully melted while they transporting through the central plasma field with 200 A surfacing currents. And the particles with a diameter less than 0.5×10-4 m might be fully evaporated. However, for the boron carbide (B4C) particles, only the one with a diameter less than 0.5×10-4 m could be melted in the same PTA space. Most of B4C particles are only preheated at its solid state when they were fed through the central field of PTA plasma when the surfacing current is equal to or less than 200 A. When the arc current was smaller than100 A, only the particles smaller than 0.5×10-4 m could be melted in the PTA space for the Fe-base alloy. Almost none of the discussed B4C particles could be melted in the 100 A PTA space.