Corrosion characteristics of plasma spray, arc spray, high velocity oxygen fuel, and diamond jet coated 30MnB5 boron alloyed steel in 3.5 wt.% NaCl solution
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30MnB5 boron alloyed steel surface is coated using different coating techniques, namely 60(Ni-
15Cr-4.4Si-3.5Fe-3.2B 0.7C)-40(WC 12Co) metallic powder plasma spray, Fe-28Cr-5C-1Mn
alloy wire arc spray, WC-10Co-4Cr (thick) powder high velocity oxy-fuel (HVOF), and WC-
10Co-4Cr (fine) diamond jet HVOF. The microstructure of the crude steel sample consists of
ferrite and pearlite matrices and iron carbide structures. The intermediate binders are well
bonded to the substrate for all coated surfaces. The arc spray coated surface shows the formation
of lamellae. The cross-section of HVOF and diamond jet HVOF coated surfaces indicates the
formation of WC, W2C Cr, and W parent matrix carbide structures. The corrosion characteristic
of the coated steel has been investigated in 3.5 wt.% NaCl solution using electrochemical
impedance spectroscopy (EIS), scanning electron microscope (SEM), and energy dispersive Xray
spectroscopy (EDAX) techniques. The results reveal that the steel corroded in the medium
despite the coatings. However, the extent of corrosion varies. HVOF coated sample
demonstrated the highest corrosion resistance while arc spray coated sample exhibited the least.
EDAX mapping reveals that the elements in the coatings corroded in the order of their standard
electrode potential (SEP). Higher corrosion resistance of HVOF coated sample is linked to the low SEP of tungsten.
Keywords
QD Chemistry