Effect of stoichiometry conditions on the erosion and sliding wear behaviors of Cr3C2-NiCr coatings deposited by a novel ethanol-fueled HVOF process

In this work, a novel ethanol-fueled HVOF process, as the most recently developed liquid fuel HVOF technology, was employed to prepare Cr3C2-25wt%NiCr hard-metal coatings on 304 stainless steel substrates. The influence of different stoichiometry conditions, defined as the oxygen/ethanol ratio, on the evolution of the coating microstructure was investigated in order to correlate with the properties of as-deposited Cr3C2-NiCr coatings. The results showed that the varied stoichiometry factors have little effect on the phase composition of the coating. However, they have a great influence on the microstructure and performances, including porosity, microhardness, fracture toughness, erosion resistance and sliding wear resistance. A denser Cr3C2-NiCr coating with higher erosion resistance is obtained when the stoichiometry factor is <1, being markedly different compared with the results obtained using kerosene-fueled HVOF processes. The stoichiometry factor of kerosene-fueled HVOF processes is generally slightly >1 allowing to obtain a higher quality Cr3C2-NiCr coating. The sliding wear mechanism of Cr3C2-NiCr coatings is attributed to abrasive grooving, peelings induced by cracking, fragmentation and pull-out of carbide grains, as well as delamination and tribo-oxidation.

Automated summary

This study used a novel ethanol-fueled HVOF process to prepare Cr3C2-25wt%NiCr hard-metal coatings on stainless steel substrates. The influence of different stoichiometry conditions on the microstructure and performances of the coatings was investigated. The results showed that the stoichiometry factor has little effect on the phase composition but has a significant impact on the microstructure and properties of the coatings. When the stoichiometry factor is <1, a denser and higher erosion-resistant Cr3C2-NiCr coating is obtained, which differs from the results obtained using kerosene-fueled HVOF processes.