Effect of TiO₂ on microstructure of laser cladding of nickel-based hardfacing alloy

The experiments of laser cladding of Ni-base hardfacing alloy powder added with and without TiO₂ were carried out.Microstructure of the clad layers was analyzed using scanning electron microscopy,X-ray diffraction and electron probe,and microhardness of the coatings was also measured.It is shown that microstructure of the G112+(mass fraction,%)4TiO₂ laser clad layer on 45 steel substrate consists of the fine in-situ formed phases of TiC,TiB₂,M₇C₃ and M₂₃C₆,which are distributed in the matrix of γ(NiFe) dendrites,and that the addition of TiO₂ can enhance the toughness of coatings,refine the microstructure of clad layer,suppress the formation of block phase in the laser clad layer and reduce the cracking susceptibility obviously.The microhardness distribution of G112+(mass fraction,%)4TiO₂ laser clad layer is uniform,and its average microhardness is 750 HV0.3.