Laser cladding in-situ carbide particle reinforced Fe-based composite coatings with rare earth oxide addition

Abstract

Particulate reinforced metal matrix composite (PR-MMC) has excellent properties such as good wear resistance, corrosion resistance and high temperature properties. Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles. Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements, was favorable for the formation of in-situ synthesized carbide particles. In this paper, rare earth oxide (RE 2O 3) was added into the clad powder mixture to investigate the effects of RE 2O 3 on the in-situ carbide particle formation in Fe-based composite coatings. Through the analysis using scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS) and transmission electron microscope (TEM), it was revealed that: (1) Adding RE 2O 3 to the Fe-based powder mixture could effectively reduce cracks and porosities and the coating surface was more smooth; (2) The solubility of carbon could be improved which increased the eutectic degree of the microstructure; (3) RE 2O 3 could promote the nucleation of the reinforcement particles as heterogeneous nuclei. During the precipitating process of the carbide particles, some RE 2O 3 powders still existed while others react with carbon in the melt to form rare earth carbides. Both of them acted as heterogeneous nuclei for the formation of particles.