The Preparation Of TiC Particle Reinforced Ni Matrix Composite Coating By Laser Cladding On Aluminum Alloy Surface

Aluminum alloy is widely used as light metal structural materials because of its small density, high strength, low thermal expansion coefficient, good thermal conductivity, excellent mechanical property and well weldability. But the abrasion resistance and corrosion resistance of aluminum alloy is poor and limit the further application in complex environment. In this paper, to improve the abrasion resistance and corrosion resistance on the surface of the aluminum alloy, the TiC/NiCrAl/and TiC/Ni25B composite coating were prepared by laser cladding. Moreover, the microstructure, abrasion behavior and corrosion resistance of the cladding layer were analysized, aiming to provide theoretical basis and certain technology foundation, and improving the abrasion resistance and corrosion resistance properties of aluminum alloy.In this paper, the phases of the coating was analysized by using X-ray diffraction (XRD) and energy disperse spectroscopy (EDS). The macro morphology and microstructure of the coating section were observed by optical microscope (OM) and scanning electron microscope (SEM). The microhardness of the coating cross-section was tested by microhardness meter; The abrasion property and corrosion resistance of cladding coating were tested by the aid of abrasion tester and electrochemical workstation.The XRD phase analysis displayed that the main phase of the TiC/NiCrAl and TiC/Ni25B coating are AINi, Al3Ni2, TiC, and Cr13Ni5Si2, in TiC/Ni25B coating also found a small amount of Cr23C6and CrB phases.The morphology and microstructure of the coating was observed by OM and SEM. The results show that, the coating with metallurgy combined characteristics can be prepared in aluminum alloy surface, internal coating without apparent porosity and crack. The microstructure from the bottom to top of the TiC/NiCrAl coating is dendrite crystal, cellular crystal, columnar dendtite crystal and equiaxed crystal, respectively. The microstructure from the bottom to top of the TiC/Ni25B coating is lamellar dendrite, slender primary acicular dendrite and interdendritic eutectic.The EDS analysis diaplayed that the phase of TiC/NiCrAl coatingfrom the lower part to the upper part are Al3Ni2and AINi respectively. From the bottom to the top of the TiC/Ni25B coating, the Al:Ni atomic ratio decreasing, explain that the transition of phase from Al3N12to AINi, meanwhile, the top position in the TiC/Ni25B coating discovered the existence of element Cr and C, speculate that at the top of the coating has Cr23C6hard phase.Microhardness distribution curve shows that the average microhardness value of TiC/NiCrAl coating is about676HV0.2, about4times that of the aluminum alloy substrate. The average microhardness value of TiC/Ni25B coating is about752.35HVo.2, about4.45times that of the aluminum alloy substrate.The abrasion experiment of TiC/NiCrAl and TiC/Ni25B coating show that, before25minutes, the relative abrasion resistance are3.16and3.93respectively. Under the same condition, the A390substrate exhibits serious abrasive wear and peeling characteristics, TiC/NiCrAl and TiC/Ni25B cladding layer exhibits slight abrasive wear behavior.The polarization curves and electrochemical impedance spectroscopy (EIS) in3.5%NaCl solution indicate that, the corrosion potential of the coating is more positive than the matrix, and the corrosion current density decrease significantly. Contrast the polarization curve of the TiC/NiCrAl and TiC/Ni25B coating, found that the corrosion resistance of TiC/NiCrAl coating is berrer. The coating presents capacitive reactance behavior, and the capacitive reactance arc radius of TiC/NiCrAl coating is larger than TiC/Ni25B coating, A390substrate presents capacitive reactance in high frequency area and impedance in low frequency area. TiC/NiCrAl cladding coating in a wide range of frequencies the phase angle near90°and the capacitive reactance characteristic is better. In low frequency (0.01Hz<f<10Hz), the impedance modulus value of TiC/NiCrAl coating is higher than TiC/Ni25B coating and the slope is bigger, show that corrosion resistance of the former is superior to the latter. The corrosion morphology of the cladding layer is localized pitting, the corrosion morphology of A390matrix are intergranular corrosion and denudation.