Effect of pre-oxidation on the electrochemical corrosion behavior of Ni-based coating reinforced by ceramic particles

Based on the widely use of the NiCr coating, we investigated the electrochemical corrosion behavior of the NiCr coating reinforced by MoSi2 and AT40 ceramic phases which has the potential of application in seal coating. The composite coating was prepared on the surface of the nickel-based alloy with approximately 150 mu m thick by using atmospheric plasma spraying (APS). The composite coatings were exposed in air at 650 degrees C, 900 degrees C, 1050 degrees C and 1100 degrees C for 24 h respectively and then the corrosion behavior of the coatings were analyzed by electro-chemical workstation. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) were used to analyze the microstructure and phase composition. The results show that the pre-oxidation improved the corrosion resistance substantially compared to the original coating. It was shown that the coating with ceramics addition which was pre-oxidized at 900 degrees C presents the best corrosion resistance. The influence of the ceramics particles addition and elements diffusion were discussed.