Research On Solidification Mechanism And The Abrasion Resistance (Cr_1-x,Al_x)₂O₃+Cr Coating Prepared By Reactive Plasma Spraying

In this paper,?Cr,Al?₂O₃+Cr composite coatings were prepared by using reactive plasma spraying.First of all,the solidification processes of three kinds of coating were studied.Then,the electrochemical corrosion behaviors in simulated seawater of three coatings were analyzed.Finally,their abrasion resistance and the interaction between wear and corrosion were discussed.Studies had shown that:?Cr,Al?₂O₃ solid solution in[?Cr,Al?₂O₃+Cr]coating grew in the form of dendrite crystal;the eutectic morphology was:?Cr,Al?₂O₃ solid solution was the matrix,and Cr particles uniformly dispersed in the solid solution matrix.The average particle size is less than 15nm and the morphology of Cr particles was in the form of spherical or short rod;Hypoeutectic and hypereutectic coatings of[?Cr,Al?₂O₃+Cr]consisted of proeutectic phase and eutectic structure.According to the difference of cooling conditions and liquid components,there would be divorced eutecticThe electrochemical corrosion properties and behaviors in simulated seawater of eutectic,hypoeutectic,and hypereutectic coating were evaluated using the open circuit potential measurements,the potentiodynamic polarization measurements and the electrochemical impedance measurements.The eutectic coating exhibited excellent corrosion resistance due to uniform organization and minimum porosity.The open circuit potential of hypereutectic coating and eutectic coating were not affected by the establishment of wear,but the potential of hypoeutectic coating decreased further.The reason of reducing potential of hypoeutectic coating was the existence of large Cr particles and the damage of the passivation film on the Cr particle.The corrosion current density were increased and the corrosion rates of three coatings were accelerated due to the wear effection.The increase of density was the most obvious in hypoeutectic coating.Wear made the eutectic and hypereutectic coating change their equivalent circuit in the earlier stage of corrosion;wear accelerated corrosion obviously in the later stage of corrosion,the failure time was shorter,and more serious damage appeared in the coatings.In the earlier stage of corrosion,wear had accelerated corrosion of hypoeutectic coating,and the coating damage was the most serious than other two coatings in the later stage.The wear mechanism of three coatings is abrasive wear.The abrasion rate of three coatings increased with the extension of immersion time and this indicates that corrosion promoted wear.In the three coating,hypoeutectic erosion is the most serious,and eutectic abrasion the slightest;With the extension of corrosion time,the interaction between corrosion and wear of three coating increased,and the interaction of eutectic coating was the lowest.