Effect of nano-Al 2 O 3 on erosion–corrosion behaviour of composite alloying layer under two phase flow conditions

Abstract

The present study was focused on understanding the effect of the added nano-Al₂O₃ on erosion–corrosion behaviour of composite alloying layer. The nano-Al₂O₃ reinforced composite alloying layer was prepared by duplex surface treatment, which consisted of Ni/nano-Al₂O₃ predeposited by brush plating and a subsequent surface alloying with Ni–Cr–Mo–Cu by double glow process on the surface of AISI 316L stainless steel. Current response with applied potential, potentiodynamic polarisation curve, electrochemical impedance spectroscopy and weight loss techniques were applied to evaluate the erosion–corrosion behaviour of composite alloying layer compared with the single alloying layer and 316L stainless steel under hydrodynamic conditions. Results of electrochemical measurements showed that the erosion–corrosion resistance of composite alloying layer was lower than that of single alloying layer when the rotating velocity of tested samples was below 2·51 m s⁻¹, whereas the erosion–corrosion resistance of composite alloying layer was higher than that of single alloying layer when the rotating velocity of tested samples above 2·51 m s⁻¹. The weight loss rate studies and surface analysis suggested that the dispersive undissolved nano-Al₂O₃ particles and γ′ prime (Ni₃Al) phase were helpful to improve the erosion–corrosion resistance of composite alloying layer at high rotational speed, though the γ′ prime phase was deleterious to corrosion resistance of composite alloying layer.