Enhanced Durability of Chromium-Primed MoS2 Coatings on Aluminum for Aerospace Flap Rail Slider Pads

Abstract Molybdenum disulfide (MoS2) is a widely used solid lubricant due to its excellent low-friction performance under dry sliding conditions. However, its practical application on aluminum substrates, such as those used in aircraft flap rail slider pads, is limited by poor adhesion and rapid degradation in ambient environments. This study investigates the performance of functionally layered Cr + MoS2 coatings deposited via DC magnetron sputtering onto aluminum substrates, specifically targeting their use in aircraft flap rail slider pad assemblies. Four coating architectures, MoS2, Cr + MoS2, MoS2 + Cr, and Cr + MoS2 + Cr, were fabricated and evaluated for tribological performance, adhesion, and durability. The Cr + MoS2 coating demonstrated a stable coefficient of friction (∼0.29) and over twice the wear life of pure MoS2 coatings due to the improved mechanical integrity and interfacial bonding provided by the Cr underlayer. In contrast, coatings with Cr top layers exhibited higher friction and shorter lifespans due to abrasive wear mechanisms. Surface and cross-sectional analyses confirmed that the Cr underlayer enhances load distribution, suppresses coating delamination, and mitigates contact stress-induced failure. These findings underscore the effectiveness of Cr-primed MoS2 coatings as durable and reliable solid-lubricant solutions for aluminum components in commercial and military aircraft flap rail slider systems, where long-term stability and wear resistance in ambient conditions are critical.