Reinforcing behavior and microstructure evolution of NbC in laser cladded Ni45 coating.

The microstructure evolution, microhardness and wear resistance of Ni45 composite coatings reinforced by in-situ NbC were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), electron probe microprobe analyzer (EPMA), transmission electron microscopy (TEM), digital microhardness tester and wear test machine. The results showed that the matrix was mainly composed of γ-Ni(Fe) solid solution, and the reinforcement phases consisted of Cr 23 C 6 , NbC, Cr 7 C 3 , Cr 2 B and little content of Cr 3 C 2 . In-situ NbC particles were homogeneous and heterogeneous nucleation from the Nb and C atoms dissolved in the molten pool, which was first precipitated from the Ni45 alloy liquid. With the increase of NbC designed content, the microhardness of coating increased gradually. When the designed content was 20%, in-situ NbC particles were regular and distributed homogeneously, and the composite coating exhibited excellent wear resistance which was higher 4.43 times than that of the original coating. [ABSTRACT FROM AUTHOR]