High-temperature tribological properties of a novel AlFeCoNiCr–Cr3C2 cermet coatings

Abstract

Microstructural instability of NiCr–Cr3C2 coating greatly limits its high-temperature tribological applications. In this work, we present a design concept for NiCr alloys based on an enthalpy-guided approach. A novel AlFeCoNiCr–Cr3C2 coating was fabricated using a supersonic plasma spraying followed by annealing. The high-temperature tribological results suggested that, due to the precipitation strengthening of Cr23C6 nano-grains in the interfacial transitions and the high plasticity of the disordered BCC (A2) and FCC (A1) phases in the AlFeCoNiCr alloy, the wear rate of the coating after annealing at 600 °C decreased by 47.6 % compared to the NiCr–Cr3C2 coating. The high density of mesoscopic defects further contributed to the strengthening and plasticity of the coating. After annealing at 900 °C, a net-shaped agglomeration of Cr23C6 and A2 phases accelerated oxidation diffusion and abrasive wear, leading to an increase of wear rate of coating. The produced wear debris mainly came from NiCr2O4, Cr2O3, NiO, Al2O3 and Fe2O3, where the NiCr2O4 was the product from the reaction between the Cr2O3 and NiO phases.

Keywords

• AlFeCoNiCr-Cr3C2 coating
• Supersonic plasma spraying
• Microstructure
• High-temperature tribological properties