發(fā)布時間：2018-07-25 19:18

【摘要】：鎂合金具有密度小、比強度高、減震性好以及優(yōu)異的防電磁、耐沖擊、傳熱導(dǎo)電性和切削加工性,然而其耐腐蝕性差極大地限制了其在諸多工業(yè)領(lǐng)域的廣泛應(yīng)用。為了提高鎂合金的耐腐蝕能力,本研究首先在鎂合金基體表面預(yù)鍍銅,進而化學(xué)鍍Ni-Cu-P、Ni-W-P、Ni-Mo-P三種不同的鎳基非晶態(tài)鍍層,研究了 CuS04、Na2W04、Na2Mo04添加量對三種鍍層的相組成、耐腐蝕性以及附著力等方面的影響。本文的主要研究內(nèi)容及結(jié)果如下:(1)首先在鎂合金表面直流預(yù)鍍銅作為中間層,預(yù)鍍銅表面呈細(xì)小胞狀的形貌,厚度約為2～3μm,與鎂合金基體之間沒有明顯的孔隙、裂紋等缺陷,既減小了鎂合金表面直接化學(xué)鍍鍍層的難度,又提高了化學(xué)鍍鍍層與鎂合金基體之間的附著力,從而提高了外層鍍層的耐蝕性。(2)Ni-Cu-P、Ni-W-P、Ni-Mo-P三種鍍層的表面均呈現(xiàn)大小不一的胞狀組織,表面均相對平整、結(jié)構(gòu)致密;三種鍍層均與鎂合金基體結(jié)合良好。(3)對于Ni-Cu-P鍍層,當(dāng)鍍液中CuS04的添加量為0.8 g/L時,鍍層中磷的質(zhì)量分?jǐn)?shù)為9.06%,銅的質(zhì)量分?jǐn)?shù)為4.50%,Ni-Cu-P鍍層為非晶態(tài)結(jié)構(gòu)。其極化曲線表明,Ni-Cu-P非晶態(tài)鍍層的自腐蝕電位為-0.31 V,腐蝕電流為0.0039396 A/cm2;其阻抗譜表明,鍍層具有最大的容抗弧半徑和|Z|值;全浸泡實驗中,CuS04添加量為0.8 g/L的Ni-Cu-P鍍層腐蝕后的組織最完整,腐蝕速率最低。(4)對于Ni-W-P鍍層,當(dāng)鍍液中Na2W04添加量為15 g/L,pH值為6.5時,鍍層為非晶態(tài)結(jié)構(gòu),鍍層中磷和鎢的質(zhì)量分?jǐn)?shù)分別為9.63%和1.14%;其極化曲線及阻抗譜表明,Ni-W-P鍍層的自腐蝕電位(-0.326 V)較鎂合金基體有較大的提高,而腐蝕電流(0.0027105 A/cm2)則明顯降低,并且鍍層具有最大的容抗弧半徑;浸泡實驗結(jié)果表明,鍍液中Na2W04添加量為15 g/L的Ni-W-P非晶態(tài)鍍層腐蝕速率最低,耐腐蝕性最佳。(5)對于Ni-Mo-P鍍層,當(dāng)鍍液中Na2MoO4的添加量為0.4 g/L,溶液pH為9.5時,鍍層中鉬的質(zhì)量分?jǐn)?shù)為9.76%,而磷的質(zhì)量分?jǐn)?shù)為9.29%;鍍層為非晶態(tài)結(jié)構(gòu);其極化曲線和阻抗譜表明,Ni-Mo-P非晶態(tài)鍍層的自腐蝕電位為-0.26 V,腐蝕電流為0.0087246 A/cm2,并且具有最大的容抗弧以及|Z|值;全浸泡實驗結(jié)果表明,鍍液中Na2MoO4添加量為0.4 g/L的Ni-Mo-P非晶態(tài)鍍層耐腐蝕性最佳。
[Abstract]:Magnesium alloy has small density, high strength, good shock absorption and excellent anti electromagnetic, impact resistance, heat transfer conductivity and machinability. However, its poor corrosion resistance greatly restricts its wide application in many industrial fields. In order to improve the corrosion resistance of magnesium alloys, this study was first plated on the surface of magnesium alloy matrix. Three different nickel base amorphous coatings were plated with Ni-Cu-P, Ni-W-P, Ni-Mo-P. The effects of CuS04, Na2W04 and Na2Mo04 additions on the phase composition, corrosion resistance and adhesion of the three coatings were studied. The main contents and results of this paper are as follows: (1) first, the direct copper plating on the surface of magnesium alloy was used as the middle layer, and the surface of the pre plated copper was presented. The thin cell morphology, with a thickness of about 2~3 mu m, has no obvious pores and cracks between the magnesium alloy matrix and the magnesium alloy matrix, which not only reduces the difficulty of direct electroless plating on the surface of magnesium alloy, but also improves the adhesion between the electroless plating and the magnesium alloy matrix, thus improving the corrosion resistance of the coating of the outer layer. (2) three kinds of Ni-Cu-P, Ni-W-P, Ni-Mo-P. The surface of the coating is all different in size and size, the surface is relatively flat and the structure is compact. The three coatings are all well combined with the magnesium alloy matrix. (3) for Ni-Cu-P coating, when the amount of CuS04 in the plating bath is 0.8 g/L, the mass fraction of phosphorus in the coating is 9.06%, the mass fraction of copper is 4.50%, and the Ni-Cu-P coating is amorphous structure. The polarization curves show that the self corrosion potential of the Ni-Cu-P amorphous coating is -0.31 V and the corrosion current is 0.0039396 A/cm2, and the impedance spectrum shows that the coating has the maximum radii of tolerance arc and |Z| value. In the whole immersion experiment, the microstructure after the CuS04 addition of Ni-Cu-P coating with the amount of 0.8 g/L is the most complete, and the corrosion rate is the lowest. (4) for the Ni-W-P coating, when the coating is deposited, the corrosion rate is the lowest. When the addition of Na2W04 is 15 g/L and the pH value is 6.5, the coating is amorphous, and the mass fraction of phosphorus and tungsten in the coating is 9.63% and 1.14%, respectively. The polarization curves and impedance spectra show that the self corrosion potential (-0.326 V) of the Ni-W-P coating is higher than that of the magnesium alloy, and the corrosion current (0.0027105 A/cm2) decreases obviously and is plated. The layer has the largest radii of tolerance arc. The result of soaking experiment shows that the corrosion rate of Ni-W-P amorphous coating with Na2W04 adding amount of 15 g/L in the plating bath is the lowest, and the corrosion resistance is the best. (5) for Ni-Mo-P coating, when Na2MoO4 is added in the bath 0.4 g/L and pH is 9.5 in solution, the mass fraction of molybdenum in the coating is 9.76% and the mass fraction of phosphorus is 9.. 29%, the coating is amorphous, and its polarization curve and impedance spectrum indicate that the self corrosion potential of Ni-Mo-P amorphous coating is -0.26 V, corrosion current is 0.0087246 A/cm2, and it has the maximum tolerance arc and |Z| value. The result of full immersion experiment shows that Ni-Mo-P amorphous coating with Na2MoO4 addition of 0.4 g/L in the bath is the best corrosion resistance.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG174.4

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