Synergistic laser cladding and ion sulfurization strategy for in-situ FeS-WS2 solid lubrication film on CoCrFeNiW0.8 high-entropy alloy: Tribological system design and process-structure-property insight

Abstract

This work employs ion sulfurization to fabricate a sulfide solid lubricating film on CoCrFeNiW_0.8 high-entropy alloy (HEA) coatings, aiming to enhance wear resistance and friction reduction. Systematic characterization reveals the HEA coating's multiphase composition (FCC, BCC, and α-phase) with an average hardness of 521 HV_0.2. A 3.8 μm thick porous feather-like FeS-WS₂ solid lubricating film was formed on the surface of the CoCrFeNiW_0.8 HEA coating, and the bonding force of this film to the HEA coating reached 43.9 N. Tribological tests revealed that the ion sulfurized HEA exhibited a 73.3 % reduction in friction coefficient (from 0.45 to 0.12) and a wear rate reduced to 52.4 % of the untreated HEA (from 4.2 mg to 2.2 mg) under a 3 N applied load. The lubricating film maintains stable low friction (0.11–0.15) across 1.5–4.5 N loads but loses its friction-reducing ability when the normal load reaches 5 N. Wear mechanism analysis identifies distinct transitions: untreated HEA progresses from abrasive to abrasive-fatigue wear, while the sulfurized coating exhibits mild abrasive wear through synergistic FeS-WS₂ lamellar lubrication and HEA substrate support. This study develops a wear-resistant tribological system combining the CoCrFeNiW_0.8 HEA substrate and the in-situ FeS-WS₂ solid lubricant film with strong interfacial adhesion. The synergy between HEA design and ion sulfurization technology establishes a new strategy for high-performance anti-wear applications.