Effect of CeO2 addition on microstructure and mechanical properties of in-situ (Ti, Nb)C/Ni coating.

Abstract As a surface repair and strengthening technology, (Ti, Nb)C/Ni coatings with different amount of CeO 2 were fabricated to repair the automobile dies. The phase constitution, microstructure, texture characteristics of oriented growth, micro-hardness, tensile properties and the action mechanism of CeO 2 were investigated. The results showed that the diffraction peaks of γ-Ni(Fe), (Ti, Nb)C, Cr 7 C 3 and Cr 23 C 6 drifted slightly as a result of solute atoms incorporation. The compact and homogenized microstructure of coatings was dominated by small striped precipitated phases and particles according to SEM and TEM results. The size of (Ti, Nb)C particles were suppressed by rare earth element Ce, which was prone to accumulate at the interface of grain boundary or crystalline phases. The unmelted CeO 2 can also become the heterogeneous nucleation basement of (Ti, Nb)C, Cr 23 C 6 and Cr 7 C 3 particles. EBSD results showed that the grain growth orientation of coatings was changed by the effect of CeO 2 on the fluidity of molten pool, as well as the growth of particles. In addition, the tensile properties of coatings were improved, and the fracture behavior was transformed from the quasi-cleavage fracture to brittle fracture with the increase of CeO 2 addition. Highlights • (Ti, Nb)C/Ni coatings with different amount of CeO 2 addition were fabricated utilizing laser cladding technology. • Proper content of CeO 2 has the effect of improving the microstructure and tensile properties. • The growth orientations of particles in the coatings were perpendicular to laser cladding direction according to the EBSD results. • The action mechanism of rare earth oxides CeO 2 was discussed systematically. [ABSTRACT FROM AUTHOR]