ISSN   1004-0595

CN  62-1224/O4

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不同NiCr含量的NiCr-Cr3C2涂层高温冲击磨损行为研究

Impact Wear Behavior of NiCr-Cr3C2 Coatings with Different NiCr Contents at High Temperature

  • 摘要: 通过超音速火焰喷涂制备了35% NiCr-Cr3C2涂层及25% NiCr-Cr3C2涂层,利用自研的高温铁屑冲击磨损试验机,在630 ℃及铁屑冲蚀的环境下进行了不同次数下的冲击试验(1×104、2×104和5×104),研究了2种涂层在铁屑冲蚀环境下的高温冲击磨损行为. 结果表明:在高温铁屑环境下35% NiCr-Cr3C2涂层和25% NiCr-Cr3C2涂层的损伤机理均为塑性变形和磨粒磨损,在相同冲击次数下两者的磨损面积相差不大,但25% NiCr-Cr3C2涂层能量吸收量及吸收率和磨损体积均小于35% NiCr-Cr3C2涂层,表现出了更好的耐高温冲击磨粒磨损性能;随着冲击次数的增加,2种涂层的冲击能量、能量吸收率及磨损面积均呈增长趋势,表明2种涂层发生了更多的塑性变形和材料去除;2种涂层的磨损体积随着冲击次数的增加呈现出不同的变化规律,25% NiCr-Cr3C2涂层的磨损体积随冲击次数的增加而增加,而35% NiCr-Cr3C2涂层的磨损体积则随冲击次数的增加呈现先增大再减小的规律.

     

    Abstract: Steam turbine is a kind of power machinery that converts the heat energy generated by fuel combustion into mechanical energy for driving power generation, and is the key equipment of coal power units, nuclear power units, gas and steam cycle generating units and other units. In the actual work of the steam turbine, due to the influence of high temperature, high pressure steam, high pressure fluid, etc., the key components of the steam turbine are susceptible to corrosion, mechanical damage, impact wear and other problems. In order to extend the service life of these components, a protective coating is usually applied on the surface of the components by various processes. NiCr-Cr3C2 coating prepared by thermal spraying technology has excellent high temperature wear resistance and corrosion resistance, and has the potential to serve as a protective coating for turbine components. At present, there have been many studies on the properties of NiCr-Cr3C2 coating, but there are few reports on the impact wear behavior of this coating under high temperature environment. In this paper, 35% NiCr-Cr3C2 coating and 25% NiCr-Cr3C2 coating with different NiCr content were prepared by supersonic flame spraying. The real service condition of steam turbine was simulated by using a self-developed high-temperature iron chip impact wear tester. Impact tests (1×104, 2×104 and 5×104) were carried out at 630 ℃ and under the environment of iron filings erosion. The impact wear behavior of the two coatings under the environment of iron filings erosion at high temperature was studied through the dynamic response during impact and the wear pattern after impact. The dynamic response data in the impact process mainly included the impact velocity curve and the impact force curve, which were collected by the corresponding sensor. The macroscopic morphology of the wear marks was observed by ultra depth of field optical microscope, and the microscopic morphology of the surface and cross section of the wear marks was observed by scanning electron microscope. The maximum wear depth and wear area and volume of the wear mark were obtained by measuring the contour of the wear mark with white light interferometer. The distribution of elements on the surface and cross section of the abrasion were analyzed by energy dispersive spectrometer. The results showed that the damage mechanisms of 35% NiCr-Cr3C2 coating and 25% NiCr-Cr3C2 coating were plastic deformation and abrasive wear, and the wear areas of the two coatings were not different under the same impact times. With the increase of impact times, the impact energy, energy absorption rate and wear area of the two coatings all showed an increasing trend, while the peak value of impact force showed a decreasing trend, that was, with the increase of impact times, more material removal and plastic deformation occurred in the two coatings. The wear volume of 25% NiCr-Cr3C2 coating increased with the increase of impact times, and under the same impact times, the energy absorption amount, absorption rate and wear volume of 25% NiCr-Cr3C2 coating were smaller than that of 35% NiCr-Cr3C2 coating, showing better resistance to high temperature impact wear. In the high temperature environment, the iron filings had good durability and were easy to be compacting by the impact ball and became the third body between the impact ball and the impact sample. As the formation of this third body would fill part of the pits on the wear marks, the wear volume of 35% NiCr-Cr3C2 coating would first increase and then decrease with the increase of impact times.

     

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