Study On Processes And Properties Of Electroless Composite Coating Ni-P-Ti₃AlC₂

Electroless Ni-P alloy coating is well known of their excellent properties. As a new ternary layered ceramic, Ti₃AlC₂ has the advantages of high hardness, thermal stability and corrosion resistance. Therefore, introducing Ti₃AlC₂ particles into Ni-P alloy would improve performances of the coating. In this paper, the bath formula and process parameters of electroless Ni-P-Ti₃AlC₂ are obtained by orthogonal experiments. The morphologies, phase, hardness, wear resistance, corrosion resistance and high temperature oxidation resistance of the composite coating are studied.The Ni-P-Ti₃AlC₂ composite coating with smooth and compact surface and good bonding with matrix metal was prepared through optimizing process parameters, and the coating rate is 21?m/h. Phase and morphology analysis show that Ti3AIC2 particles with homogeneous distribution are composted successfully on the Ni-P substrate. The polarization curve results indicate that corrosion current density of the composite coating is 2.62?A·cm-2 in 3.5mass% NaCl solution, which corrosion rate is similar with that of the Ni-P coating. The oxidation resistance of the composite coating is better than that of the Ni-P coating at 300??400??500? and 600?. The oxidation rate increases with the increasing temperature. The best microhardness and wear resistance are obtained after 400?. Under this condition, the microhardness value is 873.4HV and the wear weight loss is 4.37mg/cm2.The erosion test of the coatings in the oil water shows that Ni-P-Ti₃AlC₂ composite coating's property of anti-erosion is the best. The erosion resistance of composite coating is 4.7 times higher than that of the substrate, and is 2 times higher than that of the Ni-P coating. The erosion test of the coatings in the slurry media shows that Ni-P-Ti₃AlC₂ composite coating's property of anti-erosion is 6.1 times higher than that of the substrate, and is 3.3 times higher than that of the Ni-P coating. The erosion test of the coatings in the coal slurry media shows that Ni-P-Ti₃AlC₂ composite coating has the best property of anti-erosion, which erosion resistance is 2.7 times higher than that of the substrate, and is 1.3 times higher than that of the Ni-P coating when the coal slurry contains 30vol% coal powder.