Characterization of slurry-based mullite coating deposited on P91 steel welds

Ceramic coatings are widely used as thermal and environment barrier coatings due to their inert properties and capability to withstand high temperature. Ceramic coatings are commonly deposited by air plasma spray process and electron beam physical vapor deposition. In the present work, a cost-effective, slurry-based dip coating technique was developed to deposit mullite-based ceramic coating on the P91 steel substrate. The coating has been characterized by X-ray diffraction technique and scanning electron microscopy. Sintering of coatings was carried out in the temperature range of 900-1000 degrees C. Sintering time was varied between 0.5 and 1h. Energy dispersive spectroscopy was carried out to study the distribution and diffusion of constituent elements during high-temperature sintering. Potentiodynamic polarization tests and thermo-gravimetric analysis were performed to investigate the corrosion behavior of the coating. The coating sintered at 1000 degrees C was found to be free from cracks and other microdefects. The corrosion rate of coating sintered at 1000 degrees C was found to be 26.06mpy whereas the uncoated sample showed a higher corrosion rate of 153.7mpy.