【作者】 闫磊；

【导师】 杨川；

【作者基本信息】 西南交通大学 ， 材料科学与工程， 2013， 硕士

【摘要】 活塞环作为发动机的重要组成部件,在发动机工作过程中起着至关重要的作用。而活塞环的工作环境比较恶劣,要求活塞环具有较高的耐磨和耐蚀性能。因此,活塞环在使用前必须经过表面处理。目前,活塞环的表面处理方式主要是镀铬和氮化,但是镀铬对于环境污染较大。氮化后主要靠化合物层起耐磨作用,但对于铸铁活塞环,氮化后的化合物层较浅,因此有必要提高化合物层的厚度。本论文以常规球墨铸铁活塞环为材料,探索能够得到具有更好耐磨性和耐蚀性化合物层的新工艺。实验对球墨铸铁活塞环进行氮化、多元共渗、复合处理三种热处理工艺。对处理后的三种样品采用光学和激光共聚焦显微镜进行显微组织分析；采用XRD进行物相分析；测试它们的力学性能,如硬度和耐磨性；最后,通过盐雾腐蚀实验和电化学极化曲线对抗腐蚀性能进行分析。微观结构表明：材料经以上三种工艺后,表面都形成了化合物层,其中复合处理后的化合物层最深,达到27μm,是常规氮化处理得到化合物层厚度的9倍；多元后的化合物层12μm,是氮化的4倍。硬度试验结果表明,氮化后化合物层硬度875HV0.05,多元后硬度905HV0.05,而复合后的硬度为780Hv0.05。摩擦磨损实验表明,复合处理工艺耐磨性能最好,多元的次之,氮化的最差。盐雾腐蚀实验表明,氮化抗蚀性是原材的6倍,多元共渗后的耐蚀性是原材的8倍,而复合处理后可以达到原材的64倍。极化曲线实验也证明了耐蚀性能,复合的最好,多元的次之,氮化的最差。综上所述,涂Cr、Ti膏剂表面处理+低温气体多元共渗的复合处理新工艺可以获得较厚的化合物层,并且具有优良的耐磨性及耐蚀性能。更多还原

【Abstract】 Piston ring is one of the most important parts of engine, and it plays a vital role in the working process. Better wear and corrosion resistance is required for the severe work condition of the piston ring. Only the piston ring undergone surface treatment can be employed in the engine. At present, the main heat treatments of piston ring are nitriding and chroming. However, chroming is harmful to the environment. The excellent wear resistance after nitriding depends on the thickness of compound layer. However, the compound layer formed in the nitriding process is thin. It is necessary to enhance the thickness of the compound layer. The purpose of this paper is developing a new process, which can enhance the thickness of the compound layer with excellent wear resistance and corrosion resistance. The samples used in this paper are common piston rings, which are made of nodular cast iron.The piston rings were treated with three heat treatments:nitriding, multi-component thermochemical treatment and duplex heat treatment. Microstructures were observed by optical microscopy and laser scanning confocal microscopy; the types of phase were characterized by XRD; salt pray corrosion test and electrochemical polarization curve test were applied to compare their corrosion resistance; their hardness and wear resistance were also measured.The results show that compound layers have formed on the surface of piston rings after three heat treatments. The compound layer of duplex heat treatment is the thickest, being up to27μm. It is nine times that of nitriding. The compound layer of multi-component thermochemical treatment is12μm, which is three times thicker than that of nitriding. The hardness of the compound layer formed in nitriding process, multi-component thermochemical treatment and duplex heat treatment is905HV0.05,875HV0.05and780HV0.05respectively. The wear resistance of the compound layers listed in descend order is accordance with the results of hardness test. The results of salt spray corrosion test show that the corrosion resistance of the compound layer formed after nitriding is6times that of received sample, while that of multi-component thermochemical treatment is8times and duplex heat treatment is64times. This was also approved by the electrochemical test.In conclusion, a thicker compound layer with excellent wear resistance and corrosion resistance is forming in the duplex heat treatment process.更多还原