Tribological behavior of laser-cladded CoCrFeNi system high-entropy alloy coatings before and after immersion in 3.5 wt. % NaCl solution

In marine engineering, steels are prone to corrosion after long-term seawater immersion, while the tribological properties of coatings post-immersion-which are critical to engineering reliability-remain insufficiently investigated. To address this gap, three coatings (CoCrFeNi, CoCrFeNi-Mn, and CoCrFeNi-Al) were fabricated on Q235B steel substrates via laser cladding (laser power: 1200 W, scanning speed: 500 mm/min). Systematic tribological tests were performed before and after 90 h of immersion in 3.5 wt % NaCl solution at 17°C (simulated seawater conditions). Key findings show that CoCrFeNi and CoCrFeNi-Mn coatings possess a single face-centered cubic (FCC) phase, whereas CoCrFeNi-Al transforms into a body-centered cubic (BCC) phase, with grain size ranking as CoCrFeNi > CoCrFeNi-Mn > CoCrFeNi-Al. Before immersion, CoCrFeNi-Al exhibits optimal hardness (494.29 HV) and wear resistance (wear rate: 4.88 × 10^-5 mm³ N^-1 m^-1). After immersion, CoCrFeNi-Mn achieves the best wear resistance (wear rate: 1.23 × 10^-5 mm³ N^-1 m^-1). This work provides theoretical support and guidance for studying the tribological properties of metallic coatings after long-term immersion in marine engineering.