Influence of Ni, Al, W doping on microstructure, corrosion and wear resistance of HVOF spraying Fe-based amorphous alloy coatings

Abstract

A series of novel Fe-based amorphous alloy coatings (AACs) with outstanding corrosion and wear resistance, composed of Fe57Cr15Mo4P10C7B3M4 (M = Fe, Ni, Al and W, in at. %) with various alloying elements, were fabricated using high-velocity oxygen fuel (HVOF) technique. The effect of Ni, Al, and W on microstructure, thermal behavior, corrosion resistance, and wear resistance of these fabricated Fe-based AACs were investigated systematically compared to 316L stainless steel (316L SS) substrates. Microstructural analysis revealed that the present Fe-based AACs exhibited a dense and uniform microstructure with high thermal stability. Electrochemical test results demonstrated that doping with Ni, Al and W significantly enhanced the corrosion resistance of the base alloy AAC. The W-doped AAC showed the best performance than Ni-doped, Al-doped and base alloy AAC, with a wide passive region (ΔEpass) of 1.7 V, low self-corrosion current density (Icorr) of 1.07 × 10−6 A·cm−2 and the lowest steady-state current densities and highest passivation index. Mott–Schottky analysis and X-ray photoelectron spectroscopy results showed that the W-doped AACs forming the densest and thickest passivation films, ascribed to an increased fraction of protective and stable low-valent metal oxides (Fe2+/Cr3+/Mo4+), enhanced corrosion resistance by promoting film growth and degradation processes. Dry wear tests revealed that among these Fe-based AACs, the W-doped AAC exhibited the superior wear resistance, with the lowest coefficient of friction (0.42) and wear rate (2.8 × 10−5 mm3·N−1·m−1), because of higher amorphous content and higher hardness. Under wear conditions, the primary wear mechanisms identified for the Fe-based AACs were abrasive, fatigue, and oxidative wear.

Keywords

• Fe-based amorphous alloy coatings
• Microalloying
• Corrosion resistance
• Passivation film
• Wear resistance