Unveiling the synergistic effect of high-temperature corrosion and wear on the failure mechanisms of APS-sprayed cobalt-based coatings

In order to understand the corrosive wear behavior of abradable seal coatings in aero-engine hot-end environments, CoMoCrSi and CoCrNiW coatings were synthesized on IN718 alloys using Atmospheric Plasma Spraying (APS). The high-temperature tribological performance and failure mechanisms of these two coatings were systematically investigated in a sea salt environment across a temperature range of 400 °C to 800 °C. The results indicate that the CoMoCrSi coating exhibits superior friction and wear resistance compared to the CoCrNiW coating throughout the tested range, demonstrating better structural integrity under extreme conditions. Both coatings show a monotonic increase in coefficient of friction (COF) and wear rate with rising temperature, a phenomenon primarily attributed to the transition of the salt film from an inert, load-bearing solid third-body mediator at 400 °C to a highly reactive molten phase at 800 °C. At 400 °C, the wear mechanism for both coatings is dominated by oxidative wear. At 600 °C and above, the CoCrNiW coating suffers from a synergistic degradation process involving adhesive, corrosive, and oxidative wear, while the CoMoCrSi coating maintains a more stable protective layer due to the robust interfacial cohesion between CoMoO₄ and Na₂MoO₄ phases. The high-temperature failure is driven by the “active oxidation of chlorine” mechanism, initiated by Na₂O reacting with protective oxides to form porous scales, followed by Cl₂ penetration and the formation of volatile chlorides. This research elucidates the “thermo-mechanical-chemical” coupling effects in sea salt environments, providing a theoretical foundation and data support for the development of high-temperature protective coatings in aerospace applications.