Plasma Spraying Of Cr₃C₂-NiCr Coating And Its Applications In Remanufacturing Engineering

There are characteristics of high clear gas mixture, thermal enthalpy and reaction velocity, in-situ rapid solidification and few produce steps for plasma spraying. Plasma spraying is an important surface treatment technology. The coating is strengthening and repairing the surface of materials. At the same time, material surface will get particular properties, so plasma spraying technology is widely used in aircraft, space aircraft industries, motor manufacturing, petrochemical, textile machinery and ship industries.The Cr₃C₂-NiCr coating was prepared through plasma spraying equipment. The heating and acceleration behaviours of metal and ceramic powders during plasma spraying were studied by MATLAB software. Orthogonal experiments were conducted to find out the influence of plasma spraying parameters on the microhardness of Cr₃C₂-NiCr coating. Microstructure and mechanical properties of Cr₃C₂-NiCr coating by plasma spraying were studied by means of XRD, microscope and mechanical properties testing.It was shown that, the higher plasma spraying arc speed and the smaller the particle size, the higher the particle velocity. The coating was formed after spraying particles experiencing stages of through breeding, flight reaction and collision deposition during melting and flattening process. Influence factors in order of main to secondary are spraying distance, plasma current, flowing rate of powder gas and plasma voltage. The best processing parameters are S=100mm, I=500A, Q=7L/min, U=65V. The laminate structure coating has typical mechanical bond with the substrate. Compared with the coatings prepared by other thermal spraying, the Cr₃C₂-NiCr coating by plasma spraying has a compact structure with aboat 1.5% porosity, better microhardness between HV824 and HV900 and higher bonding strength more than 40MPa. The Cr₃C₂-NiCr coating by plasma spraying has a good abrasive resistance. The abrasion mechanism of Cr₃C₂-NiCr coating mainly is abrasive wear, and turn out a small furrow wear by ploughing and adhesive wear. In the case of erosion wear, the binding layer of coating can enhance the bond strength between matrix and Cr₃C₂-NiCr coating and it also can improve erosion resistance of Cr₃C₂-NiCr coating.The Cr₃C₂-NiCr coating by plasma spraying was applied to remanufactur the pipe seals of oil thermal recovery steam pipe and drill pipe centralizer, which indicates that remanufacturrd products operate normally. Compared with the new, these remanufactured products show the advantage of lower economic cost.