Effect of nano-CeO2 on cobalt-based alloy laser coatings

Cobalt-based alloy coatings with/without nano-CeO2 addition prepared by a 5 kW CO2 laser on Q235 low carbon steel were introduced. The effects of nanoparticles on the macro-quality, microstructure, phase composition, and wear resistance of the coatings were investigated. The microstructure and phases composition of the coatings were analyzed using Olympus-Pme-3 type microscope, Philip Xl 30 type scanning electron microscope and XD-3A type X-ray diffractometer (XRD). The wear resistance was tested using MM-200 type sliding wear machine, and the wear mechanism was analyzed by JSM-35C type scanning electron microscope (SEM). The results showed that defect (such as crack, gas hole, etc.) -free coatings were obtained. There existed γ-Co and Cr23C6 in cobalt-based alloy coatings. Another two phases of CeCo2 and ɛ-Co were identified with nanoparticles addition. Fine microstructure and equiaxed dendrite were obtained by adding nano-CeO2. The relative wear resistance is improved with the increased amount of nano-CeO2, and the coatings with the best wear resistance when laser power was 2.0 kW by adding 1.5 wt.% CeO2. The mechanism was found from abrasive/adhesive wear to fretting wear. The wear resistance decreased with 2.0 wt.% CeO2 addition.