Preparation and Electrochemical Corrosion Performance of Plasma-Sprayed NiMoCrFeW Coatings

NiMoCrFeW coatings were successfully prepared by atmospheric plasma spraying technology. The effects of spraying process parameters (spraying power and main gas flow rate) on the microstructure and mechanical properties of the coatings were investigated. The electrochemical corrosion properties of the coatings in 3.5% NaCl and 9.8% H2SO4 (wt.%) solutions were also discussed. The results showed that the microstructure of plasma-sprayed NiMoCrFeW coating was relatively dense with the uniform composition and low porosity. Different parameters had significant effects on the mechanical properties and microstructure of the coating. When the spraying power was too large, the superheated spraying powder could lead to loose microstructure. The coating was composed of a single gamma-Ni solid solution alloy phase. The change of spraying process parameters had no obvious effect on the phase composition. With the increase in spraying power, the average bonding strength of NiMoCrFeW coating increased, and the average Vickers hardness first increased and then decreased. The average bonding strength and Vickers hardness of the coating decreased with the increase in the main gas flow rate. The NiMoCrFeW coating had the highest Vickers hardness (328.9 +/- 14.7 HV0.2), higher bonding strength (65.1 +/- 1.9 MPa) and lower porosity (3.31 +/- 0.1 %) under 36-kW spraying power and 35 L/min main gas flow. Additionally, the cast iron substrate has been severely corroded in H2SO4 and NaCl solutions, while the protective efficiency of NiMoCrFeW coating on cast iron substrate was up to 98.5% in acidic environment and 76.5% in salt solution. APS NiMoCrFeW coating had good high-temperature phase stability, so that it can effectively protect the metal substrate to slow down or prevent corrosion.