Laser cladding in situ formed polyphase ceramic particle reinforced coating

The microstructure,phase,element distribution and microhardness have been analyzed with the aid of microscope,X-ray diffraction,electron probe and microhardness-tester.It is shown that there are different solidification parameters for different zones in cladding layer,hence the different microstructure.Introduction of the ceramic made the microstructure very fine.Meanwhile,the growth direction of the dendrite is various because of the presence of the ceramic particle.It has been observed that the disperse Al2O3 and TiB2 with the size of sub-micrometer formed in the grains and unreacted B2O3,TiO2 are distributed along the grain boundary.There is a ceramic density-gradient distribution along the depth of the cladding layer.The highest value of microhardness was 434HV 0.2.Experimental results show that the γ-Ni,γ',Al2O3 and TiB2 are the dominant phases in the cladding zone.The microstructure and hardness of the cladding layer are governed by the laser processing parameters and the coating's chemical composition.The hardness and the wear property of the layer are significantly enhanced due to the present of ceramic in the coating.