本文選題：激光熔覆　切入點(diǎn)：磁化處理　出處：《江西理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：激光熔覆技術(shù)不僅可強(qiáng)化機(jī)械零件的表面,還可對(duì)表面失效的零部件進(jìn)行修復(fù),所以該技術(shù)在工業(yè)中的作用將會(huì)愈來愈明顯。其顯著特點(diǎn)是在不影響基材的整體使用性能的同時(shí)還提高了需要強(qiáng)化與修復(fù)區(qū)域的表面性能,甚至還賦予它新的性能。但是鐵基涂層存在開裂、氧化、氣孔等缺陷使得該項(xiàng)技術(shù)的發(fā)展受到制約。隨著磁場(chǎng)輔助技術(shù)在各個(gè)技術(shù)復(fù)合應(yīng)用中卓見成效,且磁場(chǎng)磁化技術(shù)操作簡(jiǎn)單,綠色無污染。因此,本文主要是應(yīng)用激光熔覆基礎(chǔ)上結(jié)合磁化的復(fù)合技術(shù),研究此復(fù)合技術(shù)是否能夠起到強(qiáng)化覆層以及修復(fù)零部件表面性能的效果。本文選用常用的45鋼作為基體材料,經(jīng)調(diào)質(zhì)處理后,利用自制的磁化裝置對(duì)其預(yù)先磁化處理,首先研究了磁化對(duì)基體材料摩擦學(xué)性能和組織的影響;其次,探討了不同熔覆工藝參數(shù)的組合下所獲得涂層宏觀質(zhì)量和性能的優(yōu)異,以獲得該實(shí)驗(yàn)條件下的最佳激光工藝參數(shù);在獲得激光工藝參數(shù)后,再重新對(duì)基體磁化,然后在其表面部位激光熔覆鐵基涂層進(jìn)行實(shí)驗(yàn)研究,探索預(yù)先磁化基材對(duì)覆層摩擦學(xué)性能以及組織產(chǎn)生的影響。實(shí)驗(yàn)研究結(jié)果表明:雖然經(jīng)磁化處理后,基體的表面硬度并未有所提高,且磁化頻率過高過低時(shí),其硬度反而會(huì)有小幅的下降,但是所有經(jīng)過磁化處理后的基材試樣的耐磨性卻優(yōu)于未磁化的;同時(shí),磁化還降低了摩擦系數(shù),細(xì)化了基材組織。工藝參數(shù)對(duì)比試驗(yàn)表明熔覆層成形質(zhì)量的優(yōu)劣主要取決于掃描速度的快慢,而后是激光功率的大小;只有在參數(shù)組合較好的情況下,得到的涂層可見氣孔少,成形質(zhì)量和耐磨性也較好。磁化-激光熔覆復(fù)合實(shí)驗(yàn)結(jié)果表明基體經(jīng)過磁化處理后的涂層硬度要略高于未磁化的,耐磨性也有明顯的改善,晶粒組織得到了進(jìn)一步的細(xì)化,硬質(zhì)顆粒分布也更均勻。單獨(dú)磁化基體和磁化-激光熔覆復(fù)合的實(shí)驗(yàn)結(jié)果都表明,磁化頻率為25Hz的磁化效果最好,可認(rèn)為25Hz是本實(shí)驗(yàn)條件下的最佳磁化頻率。通過Matlab軟件,根據(jù)w-m分形函數(shù)模型進(jìn)行了二維輪廓曲線和三維輪廓曲面的模擬,探討了輪廓形貌復(fù)雜程度與分形參數(shù)的關(guān)系,二維模擬結(jié)果表明分形維數(shù)和特征尺度系數(shù)是其主要影響參數(shù),隨分形維數(shù)由1.3變化到1.9,模擬表面輪廓曲線越來越趨于復(fù)雜,即曲線形狀和幅值都在變化。對(duì)于三維輪廓曲面而言,隨分形維數(shù)由2.1增大2.9,所獲得表面輪廓形貌也越來越趨于復(fù)雜,模擬后的圖形表明分形維數(shù)仍然是影響表面輪廓曲面形貌的主要參數(shù)。
[Abstract]:Laser cladding technology can not only strengthen the surface of mechanical parts, but also repair the surface failure parts. So the role of this technology in industry will become more and more obvious. Its remarkable feature is that it improves the surface properties of the areas that need to be strengthened and repaired while not affecting the overall performance of the substrate. It has even been given new properties, but the development of the technology has been constrained by the defects of the Fe-based coating such as cracking, oxidation, porosity and so on. The magnetic field magnetization technology is easy to operate and green without pollution. Therefore, this paper mainly uses the laser cladding technology combined with magnetization technology. This paper studies whether the composite technology can strengthen the coating and repair the surface properties of the parts. In this paper, 45 steel is used as the substrate material. After the tempering and tempering, the premagnetized steel can be premagnetized by the self-made magnetization device. Firstly, the effect of magnetization on the tribological properties and microstructure of the substrate is studied. Secondly, the excellent macroscopical quality and properties of the coatings obtained by the combination of different cladding process parameters are discussed in order to obtain the best laser processing parameters under the experimental conditions. After obtaining the laser process parameters, the substrate was magnetized again, and then laser cladding the iron-base coating on the surface of the substrate was studied experimentally. The effect of premagnetized substrate on the tribological properties and microstructure of the coating was explored. The experimental results showed that the surface hardness of the substrate did not increase after magnetization, and the frequency of magnetization was too high and too low. The hardness decreases slightly, but the wear resistance of all magnetized substrate samples is better than that of unmagnetized ones, and the coefficient of friction is reduced by magnetization. The microstructure of the substrate was refined. The comparison test of process parameters showed that the quality of the cladding coating was mainly determined by the speed of scanning and the laser power, and only when the parameters were well combined, the visible porosity of the coating was less. The results of the magnetization and laser cladding experiments show that the hardness of the coating after magnetization is slightly higher than that of the unmagnetized coating, and the wear resistance is obviously improved, and the grain structure is further refined. The results of the experiments of magnetization matrix alone and magnetization laser cladding show that the magnetization frequency of 25Hz is the best, and that 25Hz is the best magnetization frequency under the condition of this experiment. According to w-m fractal function model, the two-dimensional contour curve and three-dimensional contour surface are simulated, and the relationship between the profile complexity and fractal parameters is discussed. The results show that fractal dimension and characteristic scale coefficient are the main influencing parameters. With the change of fractal dimension from 1.3 to 1.9, the simulated surface contour curve becomes more and more complex, that is, the shape and amplitude of the curve are changing. With the increase of fractal dimension from 2.1 to 2.9, the surface contour morphology becomes more and more complex. The simulated figure shows that fractal dimension is still the main parameter affecting the surface contour surface morphology.
【學(xué)位授予單位】：江西理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG174.4

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