Passivation Behavior of Fe-Based Amorphous Coatings Prepared by High-Velocity Air/Oxygen Fuel Processes
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Passivation Behavior of Fe-Based Amorphous Coatings Prepared by High-Velocity Air/Oxygen Fuel Processes H. R. Ma1,2,3 • J. W. Li1,2 • C. T. Chang1,2 • X. M. Wang1,2 • R. W. Li1,2
Submitted: 23 November 2016 / in revised form: 16 July 2017 Ó ASM International 2017
Abstract Corrosion resistance and passivation behavior of Fe63Cr8Mo3.5Ni5P10B4C4Si2.5 amorphous coatings prepared by the activated combustion high-velocity air fuel (AC-HVAF) and high-velocity oxygen fuel (HVOF) processes have been studied in detail by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, cathodic polarization and Mott–Schottky approach. The AC-HVAF coating shows higher corrosion resistance than the HVOF coating in 3.5 wt.% NaCl solution, as evidenced by its lower corrosion current density and passive current density. It is found that the superior corrosion resistance of the AC-HVAF coating is attributed to the enhanced formation of a dense passive film with less defective structure, higher pitting resistance and passivity stability, as well as stronger repassivity. Keywords amorphous metals coatings corrosion electrochemical characterization microstructure
& J. W. Li [email protected] & C. T. Chang [email protected] 1
Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, Zhejiang, China
2
Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, Zhejiang, China
3
Laboratory for Microstructures, Shanghai University, Shanghai 200444, China
Introduction Corrosion is an important issue in numerous industrial applications where it leads to significant loss of energy as well as destructive changes in materials. During the last decades, Fe-based amorphous coatings fabricated using high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes show huge application prospects in the areas involving high corrosion and wear, due to their unique combination of high hardness, good bonding strength, outstanding corrosion and wear resistance (Ref 112). Specifically, the SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 at.%) and SAM1651 (Fe48Mo14Cr15Y2C15B6 at.%) amorphous coatings have received extensive attention because of their better performance over others (Ref 1-9). However, the SAM series alloys contain a large amount of Mo (C 14 at.%) and/or Cr (C 15 at.%), leading to an increase in materials cost. Recently, we have developed an Fe63Cr8Mo3.5Ni5P10B4C4Si2.5 (at.%) amorphous coating by HVOF that exhibits corrosion resistance comparable to the SAM series amorphous coatings despite its very low Cr and Mo content (Ref 13, 14). Moreover, we have found that the Fe63Cr8Mo3.5Ni5P10B4C4Si2.5 amorphous coating fabricated by activated combustion high-velocity air fuel (AC-HVAF) shows superior wear resistance than that fabricated by HVOF during dry sliding conditions (
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