Study On Laser Cladding Amorphous Composite Coating On Ni-Al Bronze And Its Wear And Corrosion Resistance

Nickel aluminum bronze has good mechanical properties and excellent resistance to seawater corrosion,etc.It is currently the main material of ship propellers.With the development of shipping industry and the increasing demand of navigation,the propeller,as the main propulsion equipment of ships,will not only suffer from strong erosion and cavitation corrosion,but also will have sediment wear and biological contamination,etc.,the wear and corrosion resistance of nickel aluminum bronze requirements are more stringent In this paper,the influence of laser cladding（power,scanning speed）on the microstructure of the cladding layer on the surface of nickel-aluminum bronze is firstly analyzed.On this basis,the amorphous composite coating is prepared,the wear resistance and corrosion resistance of nickel-aluminum bronze composite coating and its mechanism are studied,and the service life of the propeller is further improved.The main contents and results are as follows:（1）The effects of laser power and scanning speed on microstructure of cladding coating were studied.The results show that:the phase of the cladding layer obtained under different laser process parameters is approximately the same.With the increase of laser power,the intensity of diffraction peak first decreases and then increases,and the equiaxed crystals on the upper part of the coating first decrease and then increase,with the formation of coarse dendrites.With the increase of scanning speed,the diffraction peak and peak intensity of the obtained coating decrease,the equiaxed crystal in the top region decreases,and the amorphous phase increases.The bonding area between cladding layer and substrate is composed of coarse dendrite or cellular crystal.With the increase of scanning speed,the thickness of dendrite area decreases,indicating that the increase of scanning speed is beneficial to inhibit the growth of crystal grains.（2）Cu₄₅Zr₄₇Al₈ amorphous/crystalline composite coatings were prepared,and the mechanical properties and wear resistance were studied.The results show that:at600W laser power,the microhardness and wear resistance of the coating gradually increase with the increase of scanning speed,and the change rule of amorphous content in the coating is consistent.At 700W laser power,the microhardness of the coating firstly increases and then decreases with the increase of scanning speed,and its wear resistance has no obvious change compared with that of the substrate.However,the microhardness of the coating at 800W laser power varies irregularly with the scanning speed,and its wear resistance is worse than that of the substrate.（3）The effect of laser cladding process on corrosion resistance of cladding coating and its mechanism were studied.The results show that:from the polarization curve test results,it can be seen that the matrix and coating curves are similar,and self-passivation occurs,but the passivation interval and pitting potential are different.At the laser power of 600W,with the increase of scanning speed,the self-corrosion potential gradually increases and the self-corrosion current density gradually decreases,indicating that its corrosion resistance gradually improves,which is positively related to the amorphous content in the coating.However,the corrosion resistance of 700W and 800W is also improved to some extent compared with the matrix,but there is no obvious rule.The electrochemical impedance spectroscopy radius of the coating obtained under different process parameters is larger than that of the substrate,and its variation trend is consistent with the polarization curve test results.The corrosion mechanism of the amorphous/crystalline composite coating is analyzed.