本文選題：電火花沉積 + Cr涂層��； 參考：《哈爾濱理工大學》2017年碩士論文

【摘要】：Cr涂層由于其優(yōu)異的抗腐蝕能力,普遍應用在金屬構(gòu)件的腐蝕與防護中。制備Cr涂層的方法有很多種,例如物理氣相沉積、熱噴涂、電鍍技術(shù)及電火花沉積技術(shù)等等。電火花沉積技術(shù)由于其結(jié)合強度高、熱影響區(qū)小、沉積效率高、可用于局部處理大型工件等優(yōu)點,而成為一種新興快速發(fā)展的表面處理技術(shù)。因此,本文主要通過電火花沉積表面改性技術(shù)在M50鋼基體上制備Cr涂層,研究Cr涂層組織結(jié)構(gòu)及耐腐蝕性能。采用電火花沉積技術(shù)在M50鋼基體上制備不同工藝參數(shù)(100 V-60 μF,100V-90μF,100V-120μF,150V-60μF,150V-90μF,150V-120μF)的 Cr涂層,并對涂層的沉積規(guī)律、表面形貌、物相組成、顯微結(jié)構(gòu)、硬度及孔隙率進行研究。研究結(jié)果表明:不同參數(shù)Cr涂層的單位面積增重隨著沉積次數(shù)增加而線性增加,最終保持相對穩(wěn)定的范圍內(nèi),達到極限增重;涂層表面呈現(xiàn)潑濺狀形貌,隨著電壓增大,單次脈沖沉積點尺寸增大,但電容對其影響不大;涂層表層為非晶,次表層主要為超細晶α(Fe-Cr),內(nèi)層為細晶γ(Fe-Cr);與基體相比,涂層的硬度發(fā)生下降,但是也能達到550 HV以上;不同沉積參數(shù)的涂層孔隙率在2%以內(nèi),當沉積參數(shù)太大或者較小時,孔隙率較大,當參數(shù)適中時,涂層孔隙率較小。在電化學測試方面,不同參數(shù)涂層的自腐蝕電位與基體相比,均增大,腐蝕傾向性降低,其中150 V-60μF參數(shù)涂層的自腐蝕電位最大,耐腐蝕性能最好�；w和涂層的電化學阻抗譜表現(xiàn)為一個明顯加寬的容抗弧;在浸泡試驗方面,基體的腐蝕速度明顯大于涂層的腐蝕速度,涂層抗腐蝕能力大于基體,其中150V-60μF參數(shù)涂層腐蝕速度較小,抗腐蝕能力較好。去除表面腐蝕產(chǎn)物之后,基體發(fā)生明顯的龜裂現(xiàn)象,涂層仍保持原始的潑濺狀形貌;在鹽霧試驗方面,基體失重顯著大于涂層,其中150V-60μF參數(shù)涂層的失重最少,耐腐蝕性能最好。涂層表面生成一層腐蝕產(chǎn)物,能夠有效阻止涂層進一步發(fā)生腐蝕,去除表面腐蝕產(chǎn)物之后,基體表面分布許多腐蝕坑,而涂層表面平坦無腐蝕坑。由截面照片可知,基體發(fā)生嚴重內(nèi)腐蝕,而涂層只是當縱向裂紋貫穿到基體時,腐蝕介質(zhì)通過裂紋擴散到基體,使基體發(fā)生輕微腐蝕。綜合上所述,根據(jù)電化學測試、浸泡試驗及鹽霧試驗研究基體和涂層的耐腐蝕性能,研究結(jié)果表明,涂層的耐腐蝕性能顯著優(yōu)于基體,其中150 V-60μF參數(shù)的涂層抗腐蝕能力最強。
[Abstract]:Because of its excellent corrosion resistance, Cr coating is widely used in corrosion and protection of metal components. There are many ways to prepare Cr coating, such as physical vapor deposition, thermal spraying, electroplating technology and electrospark deposition, etc., because of its high bonding strength, small heat impact zone and high deposition efficiency, the electrospark deposition technology can be used for the local area. To deal with the advantages of large workpieces and become a new and rapidly developing surface treatment technology. Therefore, in this paper, Cr coating was prepared on M50 steel substrate by electrospark deposition surface modification technology, and the microstructure and corrosion resistance of Cr coating were studied. The different technological parameters (100 V-60) were prepared by EDM technology on the matrix of M50 steel. The Cr coating of Mu F, 100V-90 mu F, 100V-120 mu F, 150V-60 mu F, 150V-90 u F, 150V-120 um F) and Study on the deposition law, surface morphology, phase composition, microstructure, hardness and porosity of the coating. The results show that the weight gain per unit area of the coating increases linearly with the increase of the number of deposition, and finally remains relatively stable. In the range, the maximum weight gain is reached; the surface of the coating is splashed, with the increase of the voltage, the size of the single pulse deposition point increases, but the influence of the capacitance on it is little. The coating surface is amorphous, the subsurface is mainly ultrafine crystal a (Fe-Cr), the inner layer is fine crystal gamma (Fe-Cr), and the hardness of the coating decreases as compared with the matrix, but it can also reach 550 HV. The porosity of the coating with different deposition parameters is less than 2%. When the deposition parameters are too large or hourly, the porosity is larger. When the parameters are moderate, the porosity of the coating is small. In the electrochemical test, the self corrosion potential of the coating increases and the corrosion tendency decreases. The self corroding electricity of the 150 V-60 mu F coating is self corroding electricity. The electrochemical impedance spectrum of the matrix and coating shows a broad tolerance arc. In the immersion test, the corrosion rate of the matrix is obviously greater than the corrosion rate of the coating. The corrosion resistance of the coating is greater than that of the matrix, in which the corrosion rate of the 150V-60 mu F coating is smaller and the corrosion resistance is better. The removal of the corrosion resistance is better. After the surface corrosion products, the matrix has obvious crack phenomenon and the coating remains original splash shape. In the salt fog test, the weight loss of the matrix is significantly greater than that of the coating. The 150V-60 mu F parameter coating has the least weight loss and the best corrosion resistance. The coating surface generates a layer of corrosion product, which can effectively prevent the coating from further corrosion. After the surface corrosion products are removed, many corrosion craters are distributed on the surface of the substrate, and the surface of the coating is flat and no corrosion pit. It is known by the cross section photographs that the matrix has serious internal corrosion, and the coating only spreads through the crack to the matrix when the longitudinal crack runs through the matrix, which makes the matrix slightly corroded. The corrosion resistance of the substrate and coating was studied by test, immersion test and salt spray test. The results showed that the corrosion resistance of the coating was significantly better than that of the matrix, and the corrosion resistance of the coating with 150 V-60 mu F parameters was the strongest.
【學位授予單位】：哈爾濱理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG174.4

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