Ascertaining the Si-substitution on the tribo-corrosion behaviors of Ti₃AlC₂ in molten Solar Salt

As a promising working medium for thermal transportation, nitrate-based molten salts are widely adopted for current concentrating solar power (CSP) plants. However, their corrosive nature also brings severe safety hazards to the system, e.g., the impellers and cover in molten salt pumps. To study the potential application of MAX ceramics as a proactive coating for these parts, tribo-corrosion behaviors of Ti₃AlC₂ and its Si-substituted analogs against GCr15 steels are evaluated in the molten Solar Salt at 300 °C to simulate the operating condition of the cold-salt pump. The Si-substituted MAXs present higher anti-wear performance than pristine Ti₃AlC₂. With an optimal composition of Ti₃Al_0.6Si_0.4C₂, about a 25% reduction in mean wear rate to that of Ti₃AlC₂ is achieved. Through a comprehensive analysis of the morphological and chemical states of both tribo-corroded and static corroded surface, the effects of Si on the tribo-corrosion behaviors of Ti₃AlC₂ is illuminated. The enhanced performance after Si addition is ascribed to the facilitated formation of aluminosilicates as corrosion products on the surface, which act as a lubricant as well as impeding the dissolution of Al into the molten Solar Salt.