Microstructure, tribocorrosion and electrochemical properties of Ti2AlC reinforced Ni60WC coatings by high-speed laser cladding

Ti2AlC was a ceramic phase with the layered structure, which had excellent corrosion resistance. In this study, Ti2AlC was added into the Ni60WC coatings with the different mass fractions by high-speed laser cladding, and the effects of Ti2AlC mass fraction on the microstructure, tribocorrosion and electrochemical properties of Ni60WC-xTi2AlC composite coatings were investigated. The results show that the Ni60WC-xTi2AlC coatings are mainly composed of fined dendritic and irregular bulk crystal structures, and their grain sizes are refined with the increase of Ti2AlC mass fraction, which improve the coating hardness. The coefficients of friction of Ni60WC-5 % Ti2AlC, -10 %Ti2AlC and- 15 %Ti2AlC coatings are 0.422,0.394, and 0.374, respectively, and the corresponding wear rates are 227.7 f 21, 218.4 f 15, and 201.5 f 22 mu m3 center dot s- 1 center dot N- 1 , respectively, indicating that the tribocorrosion properties are improved by the addition of Ti2AlC. The wear mechanism is abrasive wear, adhesive wear, and corrosion wear, in which the abrasive wear is reinforced by the addition of Ti2AlC. Moreover, the Al2O3 passive film on the Ni60WC-xTi2AlC coatings has p-n junction characteristic, which prevents the positive and negative ions from penetrating into the coating interiors. The polarization resistances of Ni60WC-5 %Ti2AlC, -10 %Ti2AlC and-15 %Ti2AlC coatings are 4.24 x 103, 1.21 x 104, and 1.40 x 104 Omega center dot cm-2, respectively, showing that the corrosion resistance of Ni60WC-xTi2AlC coatings is increased with the Ti2AlC mass fraction, which is attributed to the stable passive film by the addition of Ti2AlC.