Effect Of Cr₃C₂ And Ti On Microstructure And Wear Resistance Of Ni-based Coating Produced By Plasma Surfacing

Plasma surfacing Ni50 coating and Ni-based composite coatings?Ni+20%Cr₃C₂, Ni+20%Cr₃C₂, Ni+20%Cr₃C₂+1%Ti, Ni+40%Cr₃C₂+1%Ti? on the surface of low carbon steel were obtained by plasma surfacing. Microstructures and the phase composition of the coatings were examined by optical microscope?OP?, scanning electron microscope?SEM?, energy dispersive X-ray analysis?EDS? and X-ray diffraction?XRD?. Microhardness, sliding and impacting wear resistance, corrosion resistance of the coatings were also studied. Compared with Ni-based, Ni+Cr₃C₂, Ni+Cr₃C₂+Ti, the effects of Cr₃C₂ and Ti on microstructure and properties of plasma surfacing Ni+Cr₃C₂+Ti composite coatings were mainly discussed.The main phases of the Ni-based coating were ?-Ni, Cr₂₃C₆, CrB, Ni₃ B. The Ni+20%Cr₃C₂ composite coatings were mainly composed of ?-Ni, Cr₂₃C₆, Cr₇C₃, Cr₃C₂, CrB. Ni+40%Cr₃C₂ composite coatings were mainly composed of ?-Ni, Cr₂₃C₆, Cr₇C₃, Cr₃C₂, Cr2 B.The addition of Cr₃C₂+Ti into Ni50 coatings, there was no new phase added in the Ni+Cr₃C₂+Ti coating, however the Cr₃C₂ phase disappeared in the Ni+20%Cr₃C₂+Ti overlay welding layer.The Ni50 coating is mainly composed of ?-Ni dendrites and the eutectic structure and various compounds. The Ni+20%Cr₃C₂ composite coating mainly consisted of small uniform dendrite and compounds, and a small amount of primary chromium carbide was also found. The microstructure of Ni+40%Cr₃C₂ coating is mainly composed of a large number of primary carbides and fine dendritic structure. With the increase of Cr₃C₂ content, the hardness of Ni+Cr₃C₂ coatings were improved, but the toughness of the coating is decreased. Compared with the Ni50 coating, the spallings of Ni+Cr₃C₂ composite coating is reduced under high temperature wear condition. The furrow and plastic deformation were reduced by Sliding wear tester and Impact wear tester. However, there are large spallings and cracks in the surface of Ni+40%Cr₃C₂ coating during impact wear.The microstructure of Ni+Cr₃C₂+Ti coatings were largerly changed compared with Ni+Cr₃C₂ coatings, and the microstructure of Ni+20%Cr₃C₂+Ti was further refinement. Carbides were distributed uniform and the sizes reduced of Ni+40%Cr₃C₂+Ti. With the addition of Cr₃C₂+Ti, the hardness, wear resistance and corrosion resistance were improved of Ni+Cr₃C₂+Ti coating. Slight furrows and flakes were found in Ni+Cr₃C₂+Ti coating by sliding wear tester and impact wear tester. Under high temperature wear condition, the wear resistance of Ni+Cr₃C₂+Ti coating was better. The corrosion resistance was improved due to the microstructure refinement, solid solution strengthening.