机车气缸套等离子喷涂再制造涂层的制备及摩擦磨损性能的研究

发布时间：2018-03-31 18:29

本文选题：气缸套　切入点：等离子喷涂　出处：《扬州大学》2017年硕士论文

【摘要】：随着国民经济的高速发展,轨道交通正向高速、重载的方向发展。机车零部件的服役状态更加恶劣,失效速度加快,零部件使用寿命缩短。因此,对机车零部件的性能提出了更高要求。机车气缸套和活塞环是内燃机中最重要的摩擦副,由于磨损和穴蚀,缸套需经常更换。采用等离子喷涂技术在缸套内壁喷涂耐磨涂层,实现缸套的绿色再制造,是一项绿色环保的制造技术。本文在国内外气缸套再制造技术调研和分析的基础上,提出通过热喷涂技术对废旧气缸套实施再制造,提高缸套表面摩擦学性能,并研究其中涉及的技术问题。以NiCrBSi材料为基材,研究Al2O3和Mo材料的含量对涂层结构与性能的影响,并对所得涂层进行金相组织、相结构、显微硬度和摩擦学性能等方面的表征,比较Mo-NiCrBSi涂层在干、油以及边界润滑条件下的摩擦学性能,分析摩擦磨损机理。首先,利用等离子喷涂方法在304不锈钢基体上制备NiCrBSi涂层,涂层主要由γ-Ni、CrB、Cr2B、Ni3B等相组成,涂层存在非晶组织和晶体位错等缺陷。等离子喷涂粒子熔化较好,观察到熔融粒子在涂层内部因撞击铺展而形成的层状堆积,测量结果显示扁平粒子的厚度在5-10 μm之间,涂层孔隙率为1.72%,显微硬度约为850 HV。然后,利用胶粘混粉方式对Al2O3与NiCrBSi两种粉末进行混合,利用机械混粉方式对Mo与NiCrBSi粉末进行混合,并利用等离子喷涂方法制备Al2O3-NiCrBSi和Mo-NiCrBSi复合涂层,分析了 Al2O3和Mo含量对涂层组织结构与摩擦学性能的影响规律,基于涂层往复摩擦实验的磨痕形貌对摩擦磨损机理进行了分析。结果表明,Al2O3-NiCrBSi复合涂层由Al2O3增强体与NiCrBSi基体组成。涂层主要成分是α-Al2O3,少量β-Al2O3,以及NiCrBSi的非晶组织。Al2O3增强体含量对涂层的组织结构及耐磨性能有明显影响。Al2O3含量较少时,无法在涂层中的得到足够的强化相;Al2O3含量过多时,虽然涂层硬度较大,但是脆性也很大,没有足够的NiCrBSi固定Al2O3,在摩擦过程中易整片脱落并形成磨粒。Mo-NiCrBSi涂层中Mo颗粒熔化和铺展较好,呈现带状的扁平化粒子形貌,均匀分布在涂层中。涂层中出现了 Ni3B、Cr2B、Cr3C2等硬质相,非晶宽化现象也比较明显。随着Mo含量增加,涂层硬度逐渐降低。摩擦学测试结果显示:干摩擦条件下,涂层与对磨球在摩擦过程中形成MoO2润滑层,可降低摩擦系数并抑制磨粒的形成。干摩擦条件下,Mo-NiCrBSi涂层中的主要磨损机制是粘着磨损,Mo-NiCrBSi耐磨性能要优于Al2O3-NiCrBSi涂层。最后,针对Mo-NiCrBSi涂层开展了油润滑摩擦试验,Mo-NiCrBSi涂层在油润滑条件下摩擦系数显著下降,稳定性明显得到改善,且Mo含量对降低涂层摩擦系数有显著作用。EDS结果表明,机油摩擦过后的磨痕表面有0.34 wt%的S元素。相反,在相同条件下的非磨表面的S含量为0,表明Mo与机油发生反应生成MoS2润滑膜。随着Mo含量的增加,颗粒剥落情况越来越少,磨痕越来越浅。当Mo含量为30 wt%时,Mo-NiCrBSi涂层的磨损量仅为纯NiCrBSi涂层的4%。边界润滑条件下Mo-NiCrBSi涂层的摩擦系数曲线主要由1)最初的油润滑阶段;2)边界润滑状态;3)近乎进入干摩擦状态;4)干摩擦状态,共4个部分组成。随着Mo含量的增加,摩擦系数突变时间由NiCrBSi涂层的50分钟增加到30%Mo-NiCrBSi涂层的660分钟,表明Mo能有效延长涂层由边界润滑进入干摩擦状态的时间。
[Abstract]:With the rapid development of the national economy, is fast track traffic, the direction of heavy load. The service condition of locomotive parts even worse, the failure speed, shorten the service life of the parts. Therefore, put forward higher requirements on the performance of locomotive parts. Locomotive cylinder liner and piston ring of internal combustion engine is the most important in the friction, the wear and the cylinder liner cavitation, need to be changed frequently. The plasma spraying technology in the cylinder wall spraying wear-resistant coating, realize the cylinder green remanufacturing, it is a green manufacturing technology at home and abroad. In this paper, the cylinder sets manufacturing technology on the basis of investigation and analysis, put forward by thermal spray remanufacturing technology of waste cylinder implementation to improve the tribological properties, cylinder surface, and study the technical issues involved. Using NiCrBSi as base material, the structure and properties of the coating content on Al2O3 and Mo materials The influence and the phase composition of the coating microstructure, microhardness and tribological properties, characterization and other aspects of the comparison of Mo-NiCrBSi coating on the tribological properties of oil dry, and under the condition of boundary lubrication, the wear mechanism was investigated. Firstly, using plasma preparation of NiCrBSi coating on 304 stainless steel coating method, coating by CrB, Cr2B, -Ni gamma, Ni3B, phase composition, coating of amorphous structure and crystal dislocations and other defects. The plasma spraying particle melting well observed molten particles in the coating due to impact spreading and the formation of layered deposits, measurement results show flat particle thickness between 5-10 m coating porosity 1.72%, the micro hardness of about 850 HV. and then use adhesive mixing powder mixed with two kinds of Al2O3 NiCrBSi powder by mechanical mixing powder mixing of Mo and NiCrBSi powders, and the use of plasma Preparation of Al2O3-NiCrBSi Mo-NiCrBSi composite coating and method for coating, and analyzes the influence of Al2O3 and Mo content on the structure and Tribological Properties of coatings, wear surface coating reciprocating friction experiment was analyzed based on the mechanism of friction and wear. The results show that the Al2O3-NiCrBSi composite coating and NiCrBSi matrix composed of Al2O3 main components of coating is enhanced. Alpha -Al2O3, beta -Al2O3, NiCrBSi.Al2O3 and amorphous structure reinforcement content on Microstructure and wear resistance of the coating has obvious effect when the.Al2O3 content is small, not in the coating are strengthening enough; the content of Al2O3 is excessive, although the hardness of the coating is large, but also very brittle, no fixed NiCrBSi Al2O3 enough, in the process of friction to the whole piece off and the formation of abrasive.Mo-NiCrBSi coating of Mo particles in the melting and spreading good, showing banded flat particle shape Appearance, uniform distribution in the coating. The Ni3B coating Cr2B, Cr3C2 hard phase, amorphous wide phenomenon is also obvious. With the increase of Mo content, the hardness of the coating decreased gradually. The Tribological test results show that the dry friction condition, the coating and the grinding ball in the friction process to form a lubricating layer MoO2 the formation, the coefficient of friction can be reduced and inhibit the abrasive. The dry friction condition, the main wear mechanism of Mo-NiCrBSi coating is adhesive wear, the wear resistance of Mo-NiCrBSi is better than Al2O3-NiCrBSi coating. Finally, according to the Mo-NiCrBSi coating to carry out oil lubrication friction test, Mo-NiCrBSi coatings under oil lubrication friction coefficient decreased obviously, stability to improve, and the content of Mo to reduce the friction coefficient of the coating has a significant role in the results of.EDS showed that the oil friction after the worn surface of the S element is 0.34 wt%. On the contrary, under the same conditions of non grinding surface The content of S is 0, indicating that Mo and MoS2 formed in the reaction of oil lubricating film. With the increase of Mo content, the flaking grain is less and less, wear more and more shallow. When the Mo content is 30 wt%, the wear volume of Mo-NiCrBSi coating is only the friction coefficient curve of Mo-NiCrBSi coating 4%. boundary lubrication conditions of pure NiCrBSi coating under oil lubrication) is mainly composed of 1 initial stage; 2) boundary lubrication; 3) almost into the state of dry friction; 4) the state of dry friction, a total of 4 parts. With the increase of Mo content, the friction coefficient of NiCrBSi coating by mutation of 30%Mo-NiCrBSi coating increased from 50 minute to 660 minutes, showed that Mo extend into by the boundary lubrication state of dry friction coating time.

【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U260.6;TG174.4

【参考文献】