Effect of Nanoparticles on the Erosion-Corrosion Resistance Property of a Ni-Based Alloying Layer

Abstract

A nanoparticle reinforced Ni-based alloying layer was prepared by a duplex surface treatment on the surface of AISI 316L stainless steel. This steel contained Ni/nano-SiO2 or Ni/nano-SiC layer which was predeposited by brush plating and subsequent surface alloying with Ni-Cr-Mo-Cu by a double glow process. The microstructures of the two kinds of nanoparticles that reinforced the Ni-based alloying layers were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The corrosion behaviors of the composite layers under hydrodynamic conditions and at different rotational speeds were characterized by current responses at a potential of +0.2 V, a potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) under a static state (3.5%(w, mass fraction) NaCl solution) and under slurry flow conditions (3.5%(w) NaCl solution+10%(w) sand particles). To assess possible erosion-corrosion mechanisms, the worn sample surfaces were observed by SEM. Electrochemical tests showed that the corrosion resistance of the composite layer with the brush plated Ni/nano-SiO2 particle interlayer was slightly lower than that of the single Ni-based alloying layer produced under static state conditions. However, under hydrodynamic conditions, the corrosion resistance of the composite layer with the brush plated Ni/nano-SiO2 particle interlayer was obviously superior to that of the single Ni-based alloying layer. The corrosion resistance of the composite layer produced with the brush plated Ni/nano-SiC particle interlayer was lower than that of the single Ni-based alloying layer produced under static state and hydrodynamic conditions. From the eroded-corroded cross-section morphologies we found that highly dispersive nano-SiO2 particles were helpful in improving the erosion-corrosion resistance of the Ni-based alloying layer whereas the carbides and silicide phases were deleterious to the Ni-based alloying layer.