Microstructure and corrosion resistance of laser clad coatings with rare earth elements

摘要

The effects of rare earth oxides CeO_2 and La_2O_3 on the microstructure and corrosion re- sistance of laser clad nickel-based alloy coatings were investigated. The nickel-based alloy powder with CeO_2 or La_2O_3 was laser clad on to a steel substrate. The coatings were examined for microstructural features, compositions, phase structure and corrosion resistance. The re- sults were compared with those for coatings without CeO_2 and La_2O_3. The comparison in- dicated that the addition of CeO_2 or La_2O_3 can refine and purify the microstructure of coatings and reduce dilution of clad material from the substrate. Moreover, the addition of rare earth oxide can cause the following variations of phase structure of the coating : (a) in- crease of diffraction angle, (b) decrease of interplanar spacing, (c) reduction of lattice constant and (d) appearance of new compounds with the rare earth. The corrosion resistance of clad coating with rare earths was enhanced significantly. The mechanism of these effects is also discussed in this paper.