本文選題：氣缸套　切入點：等離子噴涂　出處：《揚州大學》2017年碩士論文

【摘要】：隨著國民經(jīng)濟的高速發(fā)展,軌道交通正向高速、重載的方向發(fā)展。機車零部件的服役狀態(tài)更加惡劣,失效速度加快,零部件使用壽命縮短。因此,對機車零部件的性能提出了更高要求。機車氣缸套和活塞環(huán)是內(nèi)燃機中最重要的摩擦副,由于磨損和穴蝕,缸套需經(jīng)常更換。采用等離子噴涂技術(shù)在缸套內(nèi)壁噴涂耐磨涂層,實現(xiàn)缸套的綠色再制造,是一項綠色環(huán)保的制造技術(shù)。本文在國內(nèi)外氣缸套再制造技術(shù)調(diào)研和分析的基礎(chǔ)上,提出通過熱噴涂技術(shù)對廢舊氣缸套實施再制造,提高缸套表面摩擦學性能,并研究其中涉及的技術(shù)問題。以NiCrBSi材料為基材,研究Al2O3和Mo材料的含量對涂層結(jié)構(gòu)與性能的影響,并對所得涂層進行金相組織、相結(jié)構(gòu)、顯微硬度和摩擦學性能等方面的表征,比較Mo-NiCrBSi涂層在干、油以及邊界潤滑條件下的摩擦學性能,分析摩擦磨損機理。首先,利用等離子噴涂方法在304不銹鋼基體上制備NiCrBSi涂層,涂層主要由γ-Ni、CrB、Cr2B、Ni3B等相組成,涂層存在非晶組織和晶體位錯等缺陷。等離子噴涂粒子熔化較好,觀察到熔融粒子在涂層內(nèi)部因撞擊鋪展而形成的層狀堆積,測量結(jié)果顯示扁平粒子的厚度在5-10 μm之間,涂層孔隙率為1.72%,顯微硬度約為850 HV。然后,利用膠粘混粉方式對Al2O3與NiCrBSi兩種粉末進行混合,利用機械混粉方式對Mo與NiCrBSi粉末進行混合,并利用等離子噴涂方法制備Al2O3-NiCrBSi和Mo-NiCrBSi復合涂層,分析了 Al2O3和Mo含量對涂層組織結(jié)構(gòu)與摩擦學性能的影響規(guī)律,基于涂層往復摩擦實驗的磨痕形貌對摩擦磨損機理進行了分析。結(jié)果表明,Al2O3-NiCrBSi復合涂層由Al2O3增強體與NiCrBSi基體組成。涂層主要成分是α-Al2O3,少量β-Al2O3,以及NiCrBSi的非晶組織。Al2O3增強體含量對涂層的組織結(jié)構(gòu)及耐磨性能有明顯影響。Al2O3含量較少時,無法在涂層中的得到足夠的強化相;Al2O3含量過多時,雖然涂層硬度較大,但是脆性也很大,沒有足夠的NiCrBSi固定Al2O3,在摩擦過程中易整片脫落并形成磨粒。Mo-NiCrBSi涂層中Mo顆粒熔化和鋪展較好,呈現(xiàn)帶狀的扁平化粒子形貌,均勻分布在涂層中。涂層中出現(xiàn)了 Ni3B、Cr2B、Cr3C2等硬質(zhì)相,非晶寬化現(xiàn)象也比較明顯。隨著Mo含量增加,涂層硬度逐漸降低。摩擦學測試結(jié)果顯示:干摩擦條件下,涂層與對磨球在摩擦過程中形成MoO2潤滑層,可降低摩擦系數(shù)并抑制磨粒的形成。干摩擦條件下,Mo-NiCrBSi涂層中的主要磨損機制是粘著磨損,Mo-NiCrBSi耐磨性能要優(yōu)于Al2O3-NiCrBSi涂層。最后,針對Mo-NiCrBSi涂層開展了油潤滑摩擦試驗,Mo-NiCrBSi涂層在油潤滑條件下摩擦系數(shù)顯著下降,穩(wěn)定性明顯得到改善,且Mo含量對降低涂層摩擦系數(shù)有顯著作用。EDS結(jié)果表明,機油摩擦過后的磨痕表面有0.34 wt%的S元素。相反,在相同條件下的非磨表面的S含量為0,表明Mo與機油發(fā)生反應生成MoS2潤滑膜。隨著Mo含量的增加,顆粒剝落情況越來越少,磨痕越來越淺。當Mo含量為30 wt%時,Mo-NiCrBSi涂層的磨損量僅為純NiCrBSi涂層的4%。邊界潤滑條件下Mo-NiCrBSi涂層的摩擦系數(shù)曲線主要由1)最初的油潤滑階段;2)邊界潤滑狀態(tài);3)近乎進入干摩擦狀態(tài);4)干摩擦狀態(tài),共4個部分組成。隨著Mo含量的增加,摩擦系數(shù)突變時間由NiCrBSi涂層的50分鐘增加到30%Mo-NiCrBSi涂層的660分鐘,表明Mo能有效延長涂層由邊界潤滑進入干摩擦狀態(tài)的時間。
[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.

【學位授予單位】：揚州大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U260.6;TG174.4

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