柱塞泵活塞工作表面激光熔覆涂层耐磨耐蚀性能研究

发布时间：2018-12-20 18:42

【摘要】：本文以工作环境恶劣的柱塞泵活塞的使用为背景,探究利用激光熔覆技术改善柱塞泵活塞工作表面的耐磨损和耐腐蚀性能,应用ANSYS仿真软件对激光熔覆这一复杂过程的温度场进行数值模拟及分析,利用激光熔覆技术在柱塞泵活塞所用材质45钢表面制备具有不同配比的Ni60+TiC复合涂层,并研究各涂层的组织形貌、显微硬度、耐磨损以及耐腐蚀性能。研究表明,激光熔覆是材料快速熔化并且凝固的过程,激光熔覆过程的温度场是一个有规律的准稳态温度场,确定了最佳的激光熔覆工艺参数。不同配比制备的激光熔覆涂层表面有差异,激光熔覆单一Ni60涂层表面较为平整致密,而Ni60+TiC熔覆涂层表面有颗粒状的凸起,且Ni60+10%TiC涂层表面有少许孔洞。激光熔覆涂层的表面硬度与基体相比明显提升,Ni60+TiC复合涂层硬度高于单一Ni60涂层,并且随着TiC添加量的增多,涂层的显微硬度也逐渐升高。激光熔覆涂层的摩擦系数与基体45钢对比有大幅度的降低,Ni60+TiC复合涂层比单一Ni60涂层摩擦系数更小,而且Ni60+20%TiC复合涂层的摩擦系数达到最佳。各激光熔覆涂层的磨损率均比基体要低,Ni60+TiC复合涂层的磨损率比单一Ni60涂层更低,Ni60+20%TiC涂层的磨损率达到最低。激光熔覆Ni60+TiC复合涂层比单一Ni60涂层的耐磨性更好,能够明显地提高45钢基体的耐磨性,并且熔覆材料在Ni60+20%TiC比例下,涂层耐磨性最佳。45钢基体的磨损机理以犁削为主,而激光熔覆涂层磨损机制为犁削与疲劳剥落综合作用,随着TiC添加量的增多,涂层表面犁削作用逐渐减弱,疲劳剥落逐渐增多。激光熔覆涂层的耐腐蚀性能明显强于基体45钢,并且Ni60+20%TiC复合涂层与Ni60+30%TiC复合涂层耐腐蚀性能比单一Ni60涂层更为优越。在激光熔覆过程中,高能量激光的照射使熔覆粉末完全熔融,扫描后熔融的材料迅速凝固,这种快速熔凝以及高温度熔池内的强烈对流,使得熔覆涂层具备均匀分布的硬质相颗粒以及细致均匀的组织结构,这些熔覆层的内部典型特征对于耐磨性和耐腐蚀性能的改善具有显著作用。
[Abstract]:Based on the use of piston in poor working environment, this paper explores how to improve the wear and corrosion resistance of piston surface by laser cladding technology. The temperature field of laser cladding is numerically simulated and analyzed by using ANSYS software. The composite coating with different ratio of Ni60 TiC is prepared on 45 steel surface of piston by laser cladding. The microstructure, microhardness, wear resistance and corrosion resistance of the coatings were studied. The results show that laser cladding is a rapid melting and solidifying process of materials, and the temperature field of laser cladding is a regular quasi-steady temperature field. The optimum technological parameters of laser cladding are determined. The surface of laser cladding coating prepared by different ratio is different. The surface of laser cladding single Ni60 coating is flat and compact, while the surface of Ni60 TiC cladding coating has granular protrusions, and there are a few holes on Ni60 10%TiC coating surface. The surface hardness of the laser cladding coating is obviously higher than that of the substrate, and the hardness of the Ni60 TiC composite coating is higher than that of the single Ni60 coating, and with the increase of the amount of TiC, the microhardness of the coating increases gradually. The friction coefficient of laser cladding coating is much lower than that of 45 steel substrate. The friction coefficient of Ni60 TiC composite coating is smaller than that of single Ni60 coating, and the friction coefficient of Ni60 20%TiC composite coating is the best. The wear rate of each laser cladding coating is lower than that of substrate, the wear rate of Ni60 TiC composite coating is lower than that of single Ni60 coating, and the wear rate of Ni60 20%TiC coating is the lowest. The wear resistance of laser cladding Ni60 TiC composite coating is better than that of single Ni60 coating, which can obviously improve the wear resistance of 45 steel substrate, and the wear resistance of the cladding material is the best under the Ni60 20%TiC ratio. The wear mechanism of 45 steel substrate is mainly ploughing. The wear mechanism of laser cladding coating is the combination of ploughing and fatigue spalling. With the increase of TiC content, the ploughing effect of the coating surface decreases gradually, and the fatigue spalling increases gradually. The corrosion resistance of laser cladding coating is obviously better than that of 45 steel substrate, and the corrosion resistance of Ni60 20%TiC composite coating and Ni60 30%TiC composite coating is better than that of single Ni60 coating. During laser cladding, high energy laser irradiation completely melts the cladding powder, solidifies the melted material rapidly after scanning, and the strong convection in the melting pool at high temperature. The cladding coating has a uniform distribution of hard phase particles and fine and uniform microstructure. These typical internal characteristics of the cladding coating play an important role in improving the wear resistance and corrosion resistance of the cladding coating.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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