Influence of Cr Content and Coating Thickness on the Microstructure and Corrosion Resistance of Ultra-high-speed Laser Cladded Martensitic Stainless Steel Coatings
Martensitic stainless steel coating of varying thicknesses were deposited by ultra-high-speed laser cladding technology.The microstructure,microhardness,and corrosion resistance of the coating under different Cr contents were analyzed.The results shows that the hardness of martensitic stainless steel coatings are significantly higher than that of the substrate.Coating with high Cr content exhibite increased martensite content.Due to the synergistic effects of martensitic strengthening,fine-grain strengthening,and dispersion strengthening,the thinner coating with higher Cr content achieve the highest hardness,reaching up to 537.71HV0.2.At the same time,due to the fine grain,higher content and more uniform distribution of Cr element,the thicker coating with higher Cr content exhibite superior corrosion resistance in electrochemical testing,with a lower corrosion current density,higher corrosion potential and the maximum arc radius and impedance values.Neutral salt spray corrosion test results shows that the intergranular Cr deficiency is the main reason of corrosion failure of martensitic stainless steel coatings.However,increasing the Cr content and its uniform distribution,along with increasing the coating thickness,hinder the penetration of corrosive media,thereby enhancing the long-term corrosion resistance of the coating.
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