Rare earth elements modification of laser-clad nickel-based alloy coatings

The effects of rare earth oxide CeO2 and La2O3 on the microstructure and wear resistance of laser-clad nickel-based alloy coatings were investigated. The nickel-based alloy powders with different contents of CeO2 or La2O3 were laser-clad on to a steel substrate. The coatings were examined and tested for microstructural features, compositions, phase structure, and wear resistance. The results were compared with those for coatings without CeO2 and La2O3. The comparison indicated that the additions of rare earth oxide CeO2 or La2O3 can refine and purify the microstructure of coatings, reduce the dilution of clad material from base metal, form some new hard crystallographic phase and increase the microhardness of the coatings. As a result, by CeO2 or La2O3 addition, the friction coefficient of the coatings was decreased and the wear resistance of the coatings was enhanced significantly. The mechanism of these effects is also discussed in this paper.