Study On The Microstructure And Properties Of Plasma-spraying/Plasma Spray Welding Coating On Copper Alloy

As a channel of hot air, the blast furnace tuyere is an extremely important part of the blastfurnace, but also hot swappable cooling element. Its life directly affects the quality of the stableoperation of the blast furnace, the production of pig iron and labor intensity. Therefore,prolonging the life of the tuyere to ensure the normal operation of blast furnace has enormouseconomic benefits. The inner wall of the blast furnace tuyere worked at high temperature above1200, long time, and mainly been subjected to the erosion of the pulverized coal and hot air,its main failure mode is wear; the outer wall of the tuyere worked at above2200, long time, ithas been subjected to liquid iron and slag erosion, and the main failure mode is oxidation onproject. Plasma spray welding technology was adopted to prepare copper-nickel alloy coating onthe surface of the copper alloy. Although the combination of the copper-nickel alloy and thecopper alloy substrate is good, the wear resistance of the copper-nickel alloy hadn’t beenimproved significantly, as well as high temperature oxidation resistance and other properties ofthe blast furnace.Different coatings on the ordinary copper alloy were prepared on the base of main failuremodes of the blast furnace tuyere by means of plasma spray welding and plasma sprayingtechnologies in this study. The microscopic morphology, phase structure, micro-hardness, wearresistance and high temperature oxidation resistance of the inner wall coatings of Ni60,NiCrCoAlY (Ni5Al) and Cr3C2-NiCr (Ni5Al) were analyzed. The microscopic morphology,phase structure, micro-hardness, thermal shock resistance and high temperature oxidationresistance of the outer wall coatings of A12O3-TiO2(NiCrAl), ZrO2-Y2O3(NiCrAl) andZrO2-Y2O3(Ni5Al) were also tested and analyzed.The wear tests of the inner wall coatings showed that, coatings of Ni60, NiCrCoAlY (Ni5Al)and Cr3C2-NiCr (Ni5Al) all had excellent wear resistance. As the temperature increasing, thewear resistance of Ni60reduced gradually, NiCrCoAlY (Ni5Al) kept the same, while the wearresistance of Cr3C2-NiCr (Ni5Al) increased significantly. Thermal shock tests showed that, thethermal shock property of NiCrCoAlY (Ni5Al) was better than that of Cr3C2-NiCr (Ni5Al).The high temperature oxidation resistance analysis of the outer wall coatings showed that,coatings of A12O3-TiO2(NiCrAl), ZrO2-Y2O3(NiCrAl) and ZrO2-Y2O3(Ni5Al) had excellenthigh temperature oxidation resistance. As time went on, the weight of each coating has slightlyincreased. Thermal shock tests showed that the thermal shock resistance of the ZrO2-Y2O3coating significantly better than that of A12O3-TiO2coating when the adhesive layer was allNiCrAl. When the insulation layer was all ZrO2-Y2O3and Ni5Al as adhesive layer, the thermalshock resistance of the coating was superior to the coating with NiCrAl as adhesive layer.Therefore, ZrO2-Y2O3and Ni5Al achieved a good match.