| 304 stainless steel has many excellent properties and has become a widely used steel. However, due to the low hardness and poor wear resistance, pits, peeling, corrosion and a series of phenomena will appear on its surface when it is used in some special environment, which reduces the lifetime severely and causes great economic loss. In order to improve the wear resistance and corrosion resistance of 304 stainless steel, self-fluxing Ni-based alloy powder were clad on 304 stainless steel surface with semiconductor laser.The influence of different laser process parameters on macro morphology, microstructure, wear resistance and corrosion resistance of the cladding coating were discussed, and the optimal laser parameters were explored, which may bring a cladding coating that have fine macro morphology, moderate dilution rate, good metallurgical combination, better abrasion resistance and corrosion resistance. The obtained parameters, to some extent, have certain practical applications and reference significance to the ball valve, which can improve the wear resistance and corrosion resistance, prolong the service life and reduce the economic loss.The experimental results showed that different laser process parameters have important influence on the cladding coating. From the upper to the lower part, the cladding coating is divided into the cladding layer, the bonding area and the heat affected zone. XRD diffraction analysis showed that there is no change in the phase composition of the cladding coating under different laser process parameters, which is composed of γ-(Ni,Fe), Cr23C6, FeNi3 and so on. Based on comprehensive analysis of the microstructure and properties, the optimum laser process parameters are as follows: the laser power is 2.5kW,the scanning speed is 4mm/s,the powder feeding rate is 300mg/s.Under the single trace cladding experiments, laser power, scanning speed and powder feeding rate have important influence on macro morphology of the Ni-based cladding coating. With the increase in laser power, the height of cladding layer decreases gradually, the width, depth and dilution rate increase gradually, the cladding layer surface becomes more smooth. With the increase in scanning speed, the height and width decrease gradually, the depth firstly decreases and then increases, the dilution increases. With the increase in powder feeding rate, the height of cladding layer firstly increases and then decreases, the width increases, the depth and dilution rate decreases. There are no obvious defects in the surface of the cladding layer, such as cracks, pores and so on.Under the single trace cladding experiments with different laser power, the macro morphology of the cladding coating are roughness and smooth when the laser power is 2.5kW, and the width of the cladding coating is 14.85 mm, the height is 1.680 mm, the depth of molten pool is 0.262 mm, and the dilution rate is 13.49. The microstructure is followed by small plane crystal, cellular shape crystal, columnar crystal, dendritic crystal, equiaxed crystal from bottom to top. The microhardness of the cladding layer reached the maximum of 619.0HV0.2 when the laser power is 2.5kW, and have good abrasion resistance. Moreover, the abrasion loss of cladding coating are far smaller than the matrix under different loading. In addition, when the laser power is 2.5kW, the corrosion resistance of the cladding coating is the best, and the self corrosion potential is-461.899 mV.Under the single trace cladding experiments with different scanning speed and different powder feeding rate, the macro morphology of the cladding coating are roughness and smooth when the scanning speed is 4mm/s and the powder feeding rate is 300mg/s, and the width of the cladding coating is 14.36 mm, the height is 1.612 mm, the depth of molten pool is 0.248 mm, and the dilution rate is 13.33. The microhardness of the cladding layer reached the maximum of 646.4HV0.2 when the scanning speed is 4mm/s. Meanwhile, the abrasion resistance is better and abrasion loss of cladding coating is smaller. When the load is 10 N, the abrasion loss is 11.5mg; when the load is 15 N, the abrasion loss is 14.7mg and when the load is 20 N, the abrasion loss is 17.6mg. Compared with the matrix, the wear property of the cladding layer is greatly improved. Moreover, when the scanning speed is 4mm/s and the powder feeding rate is 300mg/s, the corrosion resistance of the cladding coating is better, and the self corrosion potential is-286.77 mV.Under the laser cladding experiments with different lap ratio, the cladding coating has good macro morphology and excellent abrasion resistance when the lap ration is 30%。When the load is 10 N, the abrasion loss is 11.8mg; when the load is 15 N, the abrasion loss is 12.1mg and when the load is 20 N, the abrasion loss is 17.7mg. When the lap ratio is 30%, the corrosion resistance of the cladding coating is close to the matrix, and the self corrosion potential is-496.863 mV. |
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