Preparation And Study Of High Peformance Ni-based Composite Coatings

Many components and equipments failed due to wear,resulting in great damage.Although lots of surface technologies have been successfully applied to solve the problem of surface wear,there were still less solutions on the surface wear problems of components in high contact stress,for example,the repair and reinforcement of the surface on the roll.So solving this problem has important economic value.High-performance metallurgical bonding coatings were made by electro-brush plating and electric contact strengthening technology,and Ni-P alloy coating and Ni-P/Cr₃C₂ composite coating with fewer defects were obtained.The defects on the coating were few,and metallurgical bonding was formed with the substrate.The hardness of Ni-P alloy coating was 780.79HV0.1,the time of crack initiation was 80 and the time of peeling was 105 in thermal shock;The hardness of Ni-P/Cr₃C₂ composite coating was 850.90HV0.1,the time of crack initiation was 83 and the time of peeling was 128 in thermal shock.The process optimization of Ni-P alloy coating and Ni-P/Cr₃C₂ composite pre-plating coating was studied.The hardness of Ni-P alloy coating was 582.46HV0.1 and the Ni-P/Cr₃C₂ composite coating was 850.90HV0.1,the thickness of the coating was 150 um,at the same time,the boundary of the coating and substrate was clear,but there were some holes and cracks in the coating,and it needs to be further improved.It was found that when the temperature was 35 ℃ and the voltage was 12 V,the hardness and thickness of Ni-P coating were relatively good and the hardness was582.46HV0.1;The Ni-P/Cr₂C₃ plating solution was prepared by the combination of mechanical dispersion,ultrasonic dispersion and dispersion of active agent with Cr₂C₃ particles prepared by planetary ball mill.The optimal content of Cr₂C₃ was 20 g /L and the properties of Ni-P/Cr₂C₃ coating were best,which hardness was 662.97HV0.1.At the same time,brush plating process has stability and repeatability,the boundary of the Ni-P and Ni-P/Cr₃C₂ coating and the substrate were clear,but there were some holes and cracks in the coating,the substrate and the coating weremechanically bonded,so it needs to be further improved.Using electric contact technology to strengthen the pre-coating,the Ni-P alloy coating and the Ni-P/Cr₃C₂ composite coating after electric contact strengthening were further studied.It was found that after Ni-P and Ni-P/Cr₂C₃ coating were strengthened,the defects on Ni-P and Ni-P/Cr₂C₃ coatings were reduced,the fusion of the interface between the coating and substrate occurred and the hardness was increased to 781HV0.1 and 850.90HV0.1 respectively;Through the element line scan analysis,it was found that the combination of the coating and the substrate was changed from mechanical bonding into metallurgical integration by the electric contact strengthening;A further analysis by XRD showed that Ni3 P precipitated in the coating and the grain refinement may lead to the increase of hardness;Through the thermal shock analysis,it was found that thermal shock resistance was enhanced after electric contact strengthening.