| SHAN Jia-lu,AIYITI.Wurikaixi,GUO Gang.Effect of Graphene on Corrosion Resistance of Laser Cladding Nickel Base Composite Coating[J],52(5):175-188 |
| Effect of Graphene on Corrosion Resistance of Laser Cladding Nickel Base Composite Coating |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.05.017 |
| KeyWord:laser cladding graphene Ni60 acidic neutral alkaline corrosion resistance |
| Author | Institution |
| SHAN Jia-lu |
College of Mechanical Engineering, Xinjiang University, Urumqi , China |
| AIYITI.Wurikaixi |
College of Mechanical Engineering, Xinjiang University, Urumqi , China |
| GUO Gang |
College of Mechanical Engineering, Xinjiang University, Urumqi , China |
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| Abstract: |
| Laser cladding (LMD) technology can be used to manufacture 3D components, repair damaged parts and prepare high-performance coatings. It can not only maintain the original advantages of materials, but also enhance other properties of materials, such as wear resistance and corrosion resistance. In recent years, based on various excellent properties, graphene has been used as the reinforcing phase of metal matrix composites, and its properties have been studied. The work aims to study the effect of graphene (Gr) content on corrosion resistance of nickel base composite coating and determine the optimal content of Gr by analyzing the effect of Gr on the corrosion resistance of composite coating, and explore the corrosion behavior of nickel base composite coatings with different Gr contents in three solutions (acidic, neutral and alkaline) with different pH values. Q235 steel was cut into a 160 mm×70 mm×8 mm rectangle and used as the matrix for the experiment, and the rust and oxide scale on the surface were removed by an angle grinder. The surface was polished to be smooth and flat with sandpaper, and the surface of the matrix was wiped clean with absolute ethanol. Different proportions of Gr (0%, 0.3%, 0.5%, 0.8%, and 1%, mass fraction) were added to Ni60 powder as cladding powder. The uniformly mixed Gr/Ni60 powder was put into a 60 mm×40 mm mold and preset on the Q235 matrix, and the preset powder thickness was 0.8 mm. The YLS-2 000 W fiber laser was used in the experiment. The scanning speed in the cladding process was 6 mm/s, the laser power was 1 400 W, and the lap rate between two adjacent channels was 30%. The sample was cut with wire cutting machine, the coating surface was polished to be smooth, and the coating surface was corroded with aqua regia solution (V(HCl)︰V(HNO3)=3︰1), then the micro morphology of the coating surface before corrosion was observed with scanning electron microscope (SUPRA-55VP), and BRUKER X-FLASH- SDD-5010 energy spectrometer (EDS) was adopted to map the coating surface to analyze the element segregation on the coating surface. The corrosion resistance of the coating was analyzed by Linear Sweep Voltammetry (LSV) test and Electrochemical Impedance Spectroscopy (EIS) test with ChenHua CHI660E electrochemical workstation. The surface composition and elemental valence state of the coating were analyzed by semefi K-alpha + X-ray photoelectron spectroscopy tester, and the surface morphology of the coating after corrosion was observed. The Gr/Ni60 composite coating with good bonding with the matrix was successfully prepared on the surface of Q235 by laser cladding technology. The results indicated that the C and Cr elements of the composite coating with Gr were mainly distributed among the dendrites, and the intragranular regions were mainly Fe and Ni. The content of Gr increased with the increase of corrosion potential in the composite coating. Under acidic corrosion conditions, the self-corrosion potential increased with the increase of GR content, from −0.466 V to −0.384 V, and the polarization resistance also increased from 87.71 Ω/cm2 to 153.53 Ω/cm2 of pure Ni60 coating, but each coating had no obvious passivation range, mainly hydrogen evolution corrosion. Under the neutral corrosion environment, each coating had an obvious passivation range when the Gr content was 0.8wt.%, the longest passivation interval reached 0.285 V, the phase angle value and impedance mode value reached the maximum, and oxides were formed on the surface, which improved the corrosion resistance of the coating. Under the condition of alkaline corrosion, the composite coatings with five different Gr contents had a longer passivation range compared with those under the neutral corrosion environment. When the GR content was 0.8wt.%, the passivation interval length reached 1.506 V and the polarization resistance reached the highest value of 3 030.32 Ω/cm2. When the Gr content was 1wt.%, the corrosion resistance of the composite coating was not as good as that of the composite coating with Gr content of 0.8wt.% in the three corrosive environments. The addition of GR has a significant positive effect on the corrosion resistance of Ni base composite coating. The addition amount of GR has the optimal value. Excessive addition of GR will reduce the corrosion resistance of the composite coating. The corrosion resistance of the composite coating under alkaline corrosion conditions is better than that under acidic and alkaline corrosion conditions. When the content of GR is 0.8wt.%, the corrosion resistance of the composite coating is the best. |
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