Wear and Corrosion Resistance of Fe-Based Coatings Reinforced by TiC Particles for Application in Hydraulic Systems

Abstract

Thermally sprayed Fe-based coatings reinforced by TiC particles are a cost-effective alternative to carbide coatings such as WC/CoCr, Cr3C2/NiCr, and hard chrome coatings. They feature a good wear resistance and—with sufficient amount of alloying elements like Cr and Ni—also a high corrosion resistance. In hydraulic systems, the piston is usually coated with hard chrome coatings for protection against corrosion and wear. New water-based hydraulic fluids require an adaption of the coating system. In order to investigate the wear and corrosion resistance of Fe/TiC, a novel powder consisting of a FeCr27Ni18Mo3 matrix and 34 wt.% TiC was applied by HVOF and compared to reference samples made of WC/CoCr (HVAF) and hard chrome. Besides an in-depth coating characterization (metallographic analyses, electron microprobe analyzer–EMPA), wear resistance was tested under reverse sliding in a water-based hydraulic fluid. The novel Fe/TiC coatings showed good wear protection properties, which are comparable to conventional coatings like WC/CoCr (HVAF) and electroplated hard chrome coatings. Corrosion resistance was determined by polarization in application-oriented electrolytes (hydraulic fluid at 60 °C, artificial sea water at RT). The corrosion resistance of the investigated iron-based coatings at 60 °C was superior to the references coatings for both hydraulic fluids. Selected coatings were tested in an application-oriented hydraulic test bench with HFC hydraulic fluid (water polymer solutions) showing comparably good wear and corrosion resistance as the hard chrome-coated reference.