Study on Corrosion Resistance of Coating Produced by DC-Plasma Jet Surface Metallurgy
|School||Shandong University of Science and Technology|
|Keywords||DC-plasma jet surface metallurgy microstructure corrosion in seawater salt spray test pitting cavitation erosion|
In the paper, Fe-based alloy powders of corrosion-resistant have been schemed out contraposed to the characteristic of corrosive environment. DC-plasma jet surface metallurgy coating has been obtained by means of synchronous feeding and high-energy plasma beams. The macro-organization, microstructure and the rigidity of the DC-plasma jet surface metallurgy coating has been discussed in detail, the corrosion resistance of the coating has also been selective analysis.Making use of optical microscope, SEM, electron probe, X-ray diffraction etc., morphology and component features have been studied in detail. The coating near the substrate has typical flat epitaxial growth morphology and near the top has relatively regular dendritic morphology. The growth of grains is affected by crystallographic aeolotropy. The different component increased or decreased generally, but has been disturbed from microscopic view. The white-bright band, appearing between the coating and the substrate, proved metallurgical bond.Owing to the solution hardening, dispersion strengthening, and refinement strengthening, the metallurgy layer revealed high micro-hardness, and the hardness was uniform distribution during the coating.Coating by DC-plasma surface metallurgy occurs pitting both in the seawater and salt spray test, because there is a lot of corrodibility negion and dissolved oxygen in the electrolyte. The polarization curves and results of EIS showed that coating by DC-plasma surface metallurgy is more corrosion resistant than stainless steel in the seawater and salt spray test. The corrosion rate is great at the beginning of corrosion test, then it slowly reduced; after a long time, it became stabilization. The main reasons of low corrosion rate of coating by DC-plasma surface metallurgy is that: there is high content anticorrosion element and high quality of the coating and the feature of flash set and cooling.The cavitation erosion resistance of coating by DC-plasma surface metallurgy which is 1.23 times higher than that of 0Cr13Ni6Mo after 42 hours cavitation erosion. The hindrance of hard phase boundary forγ-(Fe,Ni) phase plastic deformation andγ-(Fe,Ni) phase change to martensite in the result of stress was main reason for excellent cavitation erosion resistance. Impurity, gas cavity and crack had impact for the nature of cavitation erosion resistance.