Erosive-Corrosive Wear of Thermally Sprayed Hard Coatings Using Powder and Wire Materials

Erosive-corrosive wear experiments were conducted on coatings deposited by flame spray/flexicord and high velocity oxy-fuel (HVOF) thermal spray techniques onto AISI 1020 steel substrates. Erosion tests were performed on the slurry tribometer using a combination of freshwater with quartz sand particles with a grain size of 300 to 425 μm. The study of the erosive-corrosive effect was carried out by comparing the results obtained in electrochemical corrosion tests of original and previously eroded samples, as well as samples subjected to erosive-corrosive tests under the most critical condition. A solution of 0.1 M H2SO4, with 19 g/L of Cl was used as the corrosive medium. All the coatings exhibited erosion wear mechanisms associated with brittle forms of failure due to high hardness. The worst erosion test condition was for the impact velocity of the particles of 9.33 m/s at the impact angle of 90˚. Under this condition, the erosion rate was 78.28 mm3/Kg for the FS/FC sprayed coating and 25.37 mm3/Kg for the HVOF coating. Under corrosive wear conditions, the process was predominantly influenced by the erosive component, which was favored by the low resistance to corrosion of the binder phase. The degradation mechanisms are related to the dilution of the binder phase at the interface and the extrusion of hard fillers. Factors such as the composition and microstructure of the deposits, porosity, roughness, and corrosion significantly influenced the test results. The wear mechanism reveals that the erosive component prevails in the wear-corrosion synergy.