Laser Cladding Al-si-based Nano-SiC Composite Coating On Magnesium Alloy Surface

Magnesium alloys have high strength, easy processing, recyclability, etc. Therefore, magnesium alloys are widely used in electrical and electronic, automotive, aerospace and other fields. However, due to the lower hardness of the magnesium alloy, less corrosion resistance, which largely restricts the wide application and further development of the magnesium alloy material. Therefore, how to improve the strength, hardness, corrosion resistance and other performance of magnesium alloy was become the focus of the magnesium alloy material.In this paper, the Al-Si coating, the Al-Si+5%nano SiC and Al-Si+10%nano-SiC layers were prepared on the surface of AZ31B magnesium alloy by laser cladding, the microstructure and phase of the layers were observed and analysed, the microhardness and corrosion resistance of the layers were determined.XRD analysis showed that the phase of the Al-Si cladding layer is a-Mg, Mg2Si, Mg17Al12, Al3Mg2, Al2Mg, the microstructure is composed of dendrites in the upper cladding layer, a linear arrangement of black phase in the Central cladding layer, the petal-like organization in the lower cladding layer, the maximum microhardness of the cladding layer is up’to150HV0.2, the corrosion potential higher than the matrix by0.279V, the corrosion current lower than the matrix by0.046A. The corrosion rate of the coating which was measured by weight loss method is0.158g/(cm2·h), significantly lower than the0.379g/(cm2·h) of the magnesium alloy.When the nano-SiC was add in the Al-Si coating, the microstructure and properties of the coating have undergone great changes. The phase of the Al-Si+5%nano-SiC coating is Mg2Si, Mg2C3, Mg17Al12, Al3.21Sio.47, a large number of cross-structure black phase were present in the Central of the cladding layer, the structure of the phase in the lower layer have non-obvious features, the maximum microhardness of the cladding layer is2I6HV0.2, the corrosion potential higher than the matrix by0.054V, the corrosion current lower than the matrix by0.081A, the corrosion rate dropped. The phase of the Al-Si+10%nano-SiC coating is Al, Mg, Mgi7Al12, Mg2Si, Mg2C3, Al9Si, the lower part of the cladding layer present a large number of petal-like structure which have eight petals, the maximum microhardness of the cladding layer is215HV02, the corrosion potential higher than the matrix by0.098V, the corrosion current lower than the matrix by0.072A, the corrosion rate dropped.