Effects Of Ti And CeO₂ On Microstructure And Properties Of Plasma Surfacing Co+Cr₃C₂ Composite Coatings

Plasma surfacing Co-based alloy coating(Co40) and Co-based composite coatings(Co+Cr3C2、Co+Cr3C2+1%Ti、Co+Cr3C2+1%CeO2 and Co+Cr3C2+1%Ti+1%Ce O2) on the surface of low carbon steel were obtained by plasma surfacing. Microstructures and the phase composition of the coatings were examined by optical microscope(OP), scanning electron microscope(SEM), energy dispersive X-ray analysis(EDS) and X-ray diffraction(XRD). Microhardness,wear resistance and corrosion resistance of the coatings were also studied. Compared with Co40, Co+Cr3C2, Co+Cr3C2+1%Ti and Co+Cr3C2+1%CeO2 coatings, the effects of 1%Ti and 1%CeO2 on microstructure and properties of plasma surfacing Co+Cr3C2+1%Ti+1%CeO2 composite coatings were mainly discussed.The main phases of the Co40 coating were γ-Co and Cr23C6. The Co+Cr3C2 composite coatings were mainly composed of γ-Co, Cr23C6, Cr7C3, and Cr3C2. The addition of 1%Ti into Co+Cr3C2 composite coatings, besides these phases, TiC existed in composite coatings. While adding 1%CeO2, the main phases of composite coatings were still the same.It was found that the addition of 1%Ti and 1%Ce O2 could significantly improve and enhance the surface macro-quality of Co+Cr3C2 composite coatings, and could effectively control and eliminate the formation of cracks.The Co40 coating consisted of developed γ-Co dendrite and fine eutectic structure(γ-Co+Cr23C6). The microstructure of all composite coatings was greatly refined by adding Cr3C2 particles. The Co+20%Cr3C2 composite coatings mainly consisted of fine dendrite and eutectic structure. Vast scale primary carbides and fine dendrite and eutectic structure were observed in the Co+40%Cr3C2 coating. Compared with Co40 coating, The microhardness and corrosion resistance of the Co+Cr3C2 composite coatings were obviously improved. While the microstructure of Co+Cr3C2 coatings were changed by adding 1%Ti and 1%CeO2 particles.The microstructure of Co+Cr3C2 coatings were largerly changed by adding 1%Ti particles, and the microstructure of Co+20%Cr3C2+1%Ti tranferred to equiaxed grains. Co+40%Cr3C2+1%Ti coating reduced and distributed more uniform, the dendtites and eutectic structure also get some refinement. With the addition of 1%Ti, the microhardness, wear resistance and corrosion resistance of Co+20%Cr3C2+1%Ti coating were changed slowly. While the additive content reached 40%, the hardness, wear resistance and corrosion resistance of coating with 1%Ti were improved.Compared with Co+20%Cr3C2 coating, the microstructure of coating with 1%CeO2 was more homogeneous and finer. Compared to Co+40%Cr3C2 coating, the number, shape, size and distribution of primary carbide were obviously changed. Owing to the addition of 1%CeO2, properties of the Co+Cr3C2+1%CeO2 composite coatings were significantly enhanced as compared with Co+Cr3C2 composite coatings.With the combination of 1%Ti and 1%CeO2, the microstructure of Co composite coatings were greatly improved. And performance improvement is more significant, comprehensive performance is better, especially in the Co+40%Cr3C2 composite coatings.In a word, the comprehensive properties of Co+Cr3C2+1%Ti+1%CeO2 composite coatings were the best.