Preparation And Properties Improvents Of Plasam Sprayed TiB₂-Cu Coating

TiB2-Cu and TiB2-Cu-Ni composite powers were prepared by agglomeration andsintering method. Then, TiB2-Cu coatings with different levels of TiB2and TiB2-Cu-Nicoating were deposited by plasma spraying on45#steel. The effects of composition ofslurry, parameter of spray drying on microstructure, properties of the composite powerwere analyzed in this study. The microstructure and the phase composition werecharacterized by some modern analysis technologies, including SEM, EDS, XRD, et.al.The porosity, microhardness and the wear resistance of the coating were also examined.The results show that the spray drying powder obtained at adding PEG of15%, solidcontent of60%, spray drying temperature of180℃, rotational speed of the atomizer of9600r/min has high apparent density, high flow and appropriate diameter. After sintering,the TiB2-Cu composite power mainly consists of Cu and TiB2phases. But, Ni3B, TiCphases were produced by the reaction of TiB2, Ni and C impurity in the TiB2-Cu-Nicomposit power.Coatings with denser structure could be obtained by optimizing spray parameters.The porosity of40%TiB2-60%Cu coating is1.46%, the60%TiB2-40%Cu coating is4.20%,and the60%TiB2-28%Cu-12%Ni coating is2.54%.The TiB2-Cu coating mainly consists of Cu and TiB2. The TiB2particles areeventually distributed in the coating. The TiB2-Cu-Ni coating mainly consists of TiB2,Cu-Ni solid solution and TiC. The Ni3B around the TiB2particles were oxidized in theplasma flame, resulting in the presence of large amount of Ni around the TiB2particles.There are a large number of nano-sized particle reinforcements in the metallic matrix, andthus significantly improve the hardness and strength of the composite coating.The content of TiB2increased from40%to60%, to some extent, can improve themicrohardness and wear resistance of the TiB2-Cu coating. After the incorporation of Ni,the microhardness of composite coating significantly increased, Hv0.1reached455.32, thefriction coefficient is reduced to0.194, the wear rate is reduced by about50%.