Investigation on Evolution Behavior of Carbide in Composite Carbide Reinforced Fe-based Laser Cladding Coating
The iron based powder containing TiC and Nb+C was used to prepare the composite carbide reinforced Fe-based laser cladding coating by means of the carbide compound introduction method,and the evolution behavior of the carbide in cladding coating was investigated.The results show that the decomposition of TiC and the precipitation of composite carbide can cause the changes in the chemical composition,structure,morphology,size and distribution of carbide during the cladding process.TiC is partially decomposed under the effect of laser.Ti atoms release by TiC and Nb atoms in molten pool can participate in the precipitation process of carbide,and then formed(Nb,Ti)C with C atoms.Nb can delay the crystallization process of TiC and promote the formation of amorphous phase.The undecomposed TiC can act as the heterogeneous nucleation core and promote the formation and growth of the amorphous phase and(Nb,Ti)C on its surface,then evolve into the core-shell phase.The(Nb,Ti)C by the spontaneous nucleation and growth always presents spot-shaped with small size and distributes in the grain of matrix.The discontinuous netlike(Nb,Ti)C is eutectic substance that formed in the terminal stages of solidification and distributes along the grain boundary of matrix.
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