Microstructure And Properties Of Ni-based Laser Cladding Layers

The working environment of steel parts is increasingly harsh and complex with the development of science and technology. As we all know, damage occurs generally from the surface of the material. We use laser cladding technology to improve the wear resistance and corrosion resistance of the cladding layer. We prepared three kinds of cladding layers on the surface of Q345 steel, which are Ni60A cladding layer, Ni60A+WC+Mo and Ni60A+Al2O3 cladding layers. Then a series of tests were carried out to analyze the microstructures, phase composition, wear and corrosion properties of cladding layer.A semiconductor laser-equipment was used in this experiment and process parameters are as follows. The spot size was 14mm X 2mm, the laser power was 2800W, the laser scanning speed was 450mm/min, and the multi-channel cladding lap was 50%.We found that the microstructure of Ni60A cladding layer was mainly consisted of dendrites, between which flower-shaped and massive Cr-rich precipitates distributed. As for Ni60A+WC+Mo composite cladding layer, When the amount of Mo added at 5.5wt%, the cladding layer was mainly equiaxed refined grains and the microstructure was more compact and uniform.With the addition of Al2O3, the needle-shaped and massive structure precipitated in the composite cladding layer. When the addition of Al2O3 was 14wt%, the flower-shaped structure became finer and distributed more homogeneously, and some coarse matrix phase of dendrites changed into short rod-shaped.The XRD results showed that the main component of Ni60A cladding layer is Austenite phase y-(Ni,Fe), and FeNi3, BNi3, CrsB3, CrB, Cr23C6. As for the Ni60A+WC+Mo composite cladding layer, new phases were found, such as WC, W3C, W2FeB2, Fe2MoC and Fe2MoB4. With the adding of 14wt% Al2O3, The decomposition of Al element reacts with other elements and brings phases like AlB12 and Ni2oAlBi4, AlNi3.In the performance tests, it was found that the micro hardness of Ni60A+WC cladding layer increased with the increase of Mo content. The wear loss weight ofNi60A+WC+5.5%Mo cladding layer was 5.3mg, its wear resistance is 6 times as many as Ni60A cladding layer. The chloride corrosion resistance and ability to resistant high temperature acid corrosion is 5 times and 7 times as many as Ni60A cladding layer. In the Ni60A+Al2O3 layer cladding layer, the average micro hardness is higher than Ni60A cladding layer. With the increase of the Al2O3 content, the loss weight of the composite cladding layer showed a general trend of decreasing steadily. Composite cladding layer with 14wt% Al2O3, its wear loss weight was 22.6mg, and the wear resistance is 2.6 and 1.5 times as many as Q345 steel and Ni60A laser cladding layer. In terms of corrosion resistance, Ni60A+14% Al2O3 composite cladding layer shows the optical ability of chloride corrosion resistance and resistant to high temperature acid corrosion, they are 2.3 and 3 times as many as Ni-based cladding layer.The comprehensive performance of Ni-based cladding layer with Mo and Al2O3 is better than Ni60A cladding layer, especially Ni60A+WC+5.5%Mo composite cladding layer, which has the biggest promotion in terms of surface properties. The wear resistance is 11 times that of the base material Q345 steel and 6 times that of the Ni60A cladding layer. The corrosion resistance is 5 times as many as Ni60A cladding layer, and its high temperature acid corrosion resistance ability is 7 times that of Ni60A cladding layer.