Microstructure and properties of Cr3C2-modified nickel-based alloy coating deposited by plasma transferred arc process

The nickel-based alloy with 30 wt.% chromic carbide (Cr3C2) particles has been deposited on Q235-carbon steel (including 0.12 wt.% C) using plasma transferred arc (PTA) welding machine. The microstructure and properties of the deposited coatings were investigated using optical microscope, scanning electron microscope (SEM) equiped with X-ray energy spectrometer (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), microhardness testes, and sliding wear test. It was found that the γ(Ni, Fe), M7(C,B)3, Ni4B3, and (Cr,Fe)2B phases existed in the Cr3C2-free nickel-based alloy coating obtained by PTA process. The typical hypoeutectic structure and composition segregation in the solid solution could be found clearly. The addition of 30 wt.% Cr3C2 particles led to the existing of Cr3C2 phase and the microstructure changing from hypoeutectic structure into hypereutectic structure. The composition segregation in the solid solution could not be found clearly. The average microhardness of the Cr3C2-free nickel-based alloy coating increased by 450–500 HV after the addition of 30 wt.% Cr3C2 particles. The partial dissolution of Cr3C2 particles led to the enrichment of carbon and chromium in the melten pool, and hence caused the formation of more chromium-rich carbides after the solidification process. The undissolved Cr3C2 particles and the increasing of chromium-rich carbides was beneficial to enhance the hardness and wear resistance of the Cr3C2-modified nickel-based alloy coating deposited by PTA process.