Abstract
Properties of an erosion resistant Cr3C2 - NiCr coating have been studied as a function of both plasma spraying process variables and heat treatment. The as-sprayed Cr3C2 - NiCr coating revealed low hardness value of 380-470 Hv, which provided the coating with a poor erosion resistance. This is directly attributed to the decomposition of Cr3C2 constituent into Cr7C3 and graphite phases during the spraying. It was not the effective way to control the process variables such as arc current and stand-off distance for preventing the decomposition of Cr3C2 constituent. A proper heat treatment on the as-sprayed coating increases the hardness of the coating in a great extent up to 900Hv so that the erosion resistance of the coating is clearly improved. This was confirmed to be attributed to the recovery of Cr3C2 at the expense of graphite phase and the formation of Cr2O3 by the heat treatment. In addition, the formation of Cr2O3 phase plays an important role of increasing the erosion resistance of the coating by healing the microcracks of the as-sprayed coating. These are the microstructural features responsible for the high erosion resistance of the coating after a proper heat treatment.
