Structure and electrochemical behavior of atmospheric plasma sprayed Cr3C2-NiCr cermet composite coatings

Abstract

The technical advantages and capabilities of the Metco TriplexPro-210 atmospheric plasma spray system offers the potential to develop a new protective surface to address extreme engineering requirements. The primary goal of the present work was to investigate microstructural features, mechanical properties and the electrochemical behavior of atmospheric plasma spray Cr3C2-NiCr based coatings used as erosion and corrosion-resistant materials in seal structures of gas turbines. The commercially-available 75Cr3C2–25NiCr (Metco 81NS) was used as a reference material, and blended with B4C and Cr2O3 (weight fractions of 5% and 10%) to improve properties of the newly-developed plasma sprayed coatings. Microstructural and mechanical properties were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and through microhardness indentations. The cracks and porosity levels of the as-sprayed coatings were defined using of image analysis technqiues and desnity of the coatings was masured using Archmedie's principle. Open circuit potential and linear potentiodynamic polarization studies were carried out in artificial seawater to determine the electrochemical response and corrosion degradation mechanism of the plasma sprayed coatings. The corrosion resistance of the coatings strongly depended on the coating type, crack distribution, and porosity levels.