Effect of Nb Content on the Microstructure and Mechanical Properties of a Stellite 20 Laser Clad onto Cast Steel
X-Y. Gu, H.T. Gong, Y-J. Song, X-P. Gu, H-M. Li, X-H. Zhao and L Liu
Stellite 20 layers were clad onto a ZG230-450 cast steel substrate by laser cladding with different content of Nb in the Stellite 20 powder. The microstructure evolution, phase composition, microhardness and wear properties of the laser clad Stellite 20 were studied systematically. The results showed that the phases in the laser clad Stellite 20 layers were mainly γ-Co, FeCox, M23C6, Cr3C2,CoxNb, M7C3 and NbC. The NbC phase formed in situ significantly refined the microstructure in the laser clad Stellite 20 layer. The microhardness and wear resistance of the laser clad Stellite 20 layer increased gradually with the increasing of Nb content. When the 13% Nb powders were added the microhardness of the laser clad Stellite 20 layer was 1050 HV0.5 which is about 7½ times that of the ZG230-450 cast steel substrate. Also, the wear resistance was improved to about 10.6 times that of the ZG230-450 cast steel substrate.
Keywords: Fibre laser, Co-based alloy, Stellite 20, ZG230-450 cast steel, in situ NbC, laser cladding, microstructure, microhardness, wear