Investigation of zirconium coating by sol–gel processes on A216 steel

Abstract

Steel substrates hard faced with nickel or cobalt based alloys are widely used for high-temperature and pressure applications in chemically reactive environments due to their good corrosion and wear resistance properties. The limitations of traditional hardfacing techniques are identified from various researches and nano-coating of materials is suggested as an alternate solution. In the present study, the ceramic material namely zirconium was coated on a steel substrate to improve high-temperature pitting corrosion, wear resistance, and hydrophobic property. The applicant steel substrate was coated with zirconia by sol–gel and plasma spray processes. Results indicated that bonding of zirconium with the steel substrate was influenced by stoichiometric ratio of sol–gel constituents and pH level of the sol–gel. Coating thickness obtained in first stage penetration of Zr by sol–gel coating was 540 nm. Metallographic studies showed that uniform distribution of zirconium coating along with even dispersion of the alloying elements. X-ray diffraction (XRD) analysis confirmed the presence of zirconia (ZrO) particles synthesized by sol–gel process is of nano-size. Sol–gel process exhibited better wear resistance of 2 μm compared to plasma spray process of 4 μm at higher degree of applied load through dry wear tests. The coating of the substrate using sol–gel process was found to be effective when compared with the results of the similar experiments conducted through plasma spray and hardfacing processes.