ELECTROCHEMICAL CORROSION BEHAVIOR AND MICROSTRUCTURAL CHARACTERIZATION OF HVOF SPRAYED INCONEL718-Al2O3 COMPOSITE COATINGS

Abstract

In the current experimental study, grey cast iron (CI) substrate was coated with Inconel718-Al2O3 based composite coating with a high-velocity oxy-fuel technique. The effect of changing the Al2O3 content (10, 20 and 30 wt.%) on the microstructure, hardness, porosity and electrochemical corrosion performance of Inconel (INC718) coating was studied. Investigations on the corrosion behavior of uncoated and HVOF-coated substrates were carried out at room temperature at 3.5[Formula: see text]wt.% sodium chloride solution (NaCl) with the help of the potentiodynamic polarization approach. The surface morphologies and compositions of HVOF as-sprayed and electrochemically corroded coatings were studied through SEM and EDS techniques. The various phases existing in the INC718 and Al2O3 feedstock powders and HVOF-deposited composite coatings were determined by XRD analysis. The microhardness of INC718-based coatings was found to be increased with the increase in Al2O3 content. The highest average microhardness value of about [Formula: see text]HV[Formula: see text] was observed in INC718-30[Formula: see text]wt.% Al2O3 coating. The deposited coatings exhibited an increased porosity level with the increased amount of Al2O3 contents. However, the coating with 10[Formula: see text]wt.% Al2O3 content exhibited the maximum corrosion resistance. Its improved corrosion performance is attributed to low porosity levels, which causes the penetrating pathways of Cl− ions to be blocked completely.