Magnetron-sputtered nanocrystalline/amorphous multilayers with ultrasonic surface rolling pre-treatment for hot-salt stress corrosion of TC11 alloy

Hot-salt stress corrosion cracking (HSSCC) severely restricts the service reliability of titanium-alloy compressor components in aero-engines. In this work, the effects of ion-assisted magnetron-sputtered TiAlCoSiYN/TiAlCoSiY nanocrystalline/amorphous multilayer coatings and their synergistic combination with ultrasonic surface rolling processing (USRP) on the HSSCC resistance of TC11 titanium alloy were systematically investigated. Under prolonged hot-salt stress corrosion conditions, the multilayer coatings gradually formed a continuous composite corrosion layer composed of a predominantly amorphous matrix with dispersed nanocrystals and nanoscale porosity. This composite structure creates tortuous diffusion pathways that hinder corrosive species ingress, while the nanoscale pores act as stress buffers, enhancing corrosion layer resilience. Alternating nanocrystalline nitride and amorphous metallic sublayers efficiently accommodate strain and redistribute stress under coupled thermal–mechanical loading, reducing coating cracking. The USRP–multilayer combination establishes a multiscale protective mechanism through surface mechanical state regulation and interfacial damage suppression, enhancing coating durability and markedly improving HSSCC resistance for titanium alloy. These results demonstrate an effective surface engineering strategy for improving the corrosion durability of titanium alloys under severe hot-salt service environments.