In-situ exfoliated few-layer graphene during plasma spraying: A pathway to hot corrosion-resistant Cr3C2-NiCr coatings

Hot corrosion poses a significant challenge in high-temperature industries, leading to accelerated material degradation and component failure. This study investigates the hot corrosion behavior of Cr₃C₂-NiCr coatings reinforced with in-situ exfoliated few-layer graphene in a Na₂SO₄–60wt%V₂O₅ salt environment at 900 °C. Three coating compositions were examined: pure Cr₃C₂-NiCr, 1 wt% graphene-reinforced Cr₃C₂-NiCr, and 2 wt% graphene-reinforced Cr₃C₂-NiCr coatings. The 2 wt% graphene-reinforced coating exhibited superior hot corrosion resistance, with a weight gain of 8.8 mg/cm² after 50 h of exposure, compared to 277 mg/cm² for the Cr₃C₂-NiCr coating. Microstructural analysis revealed that the reduction in crystallite size due to in-situ exfoliated few layer graphene reinforcement contributes to the formation of a more uniform and dense protective oxide layer, enhancing the overall corrosion resistance of the coatings. XPS analysis confirmed the role of exfoliated graphene in enhancing oxide layer formation and limiting the formation of detrimental compounds. The improved hot corrosion resistance is attributed to few layer exfoliated graphene's ability to refine the coating microstructure, act as a physical barrier against corrosive species, and promote the formation of a more protective oxide layer. These findings suggest that in-situ exfoliated graphene reinforcement is a promising approach for developing advanced coatings with enhanced hot corrosion resistance for high-temperature applications.