Enhancing wear resistance and mechanical performance of HVOF-sprayed Cr3C2-NiCr coatings via NiCr interlayer design

In this study, four coating systems were fabricated on Co3W3 heat-resistant steel substrate using High-Velocity Oxy-Fuel (HVOF) spraying technology: single-layer Cr3C2-25NiCr and Cr3C2-35NiCr coatings, as well as double-layer Cr3C2-25NiCr/NiCr and Cr3C2-35NiCr/NiCr structured coatings. The microstructure, phase composition, nanoindentation, and tribological performance of coatings with varying NiCr contents and double-layer structures were analyzed. The results indicated that the NiCr content and double-layer structure did not significantly affect the phase composition of the coatings. However, the introduction of a NiCr intermediate layer significantly reduced the coating porosity (from 3.02 % to 1.02 %), enhancing the coating's densification and mechanical properties. The Cr3C2-25NiCr/NiCr coating exhibited relatively higher H/E and H3/E2 values, which were 0.045 and 0.030, respectively. Tribological performance testing revealed that the double-layer structure coatings effectively alleviated stress concentration and suppressed crack propagation, improving friction and wear performance. The volumetric wear rates of Cr3C2-35NiCr/NiCr and Cr3C2-25NiCr/NiCr were reduced by 70 % and 68 %, respectively, with the wear mechanisms primarily consisting of adhesive wear, oxidative wear, and abrasive wear. Additionally, using the Williamson-Hall (W-H) approach, the key role of the NiCr intermediate layer in reducing porosity, dispersing stress, and decreasing wear in the double-layer coatings was analyzed.