【摘要】：化學(xué)鍍的鍍層在均勻性、耐蝕性、硬度、可焊性、磁性和裝飾性等性能都顯示出優(yōu)越性。作為一種優(yōu)良的表面處理工藝，已被廣泛應(yīng)用于多個(gè)領(lǐng)域，比如軍用器材、鑄模、模具、航空、紡織、食品及木材加工機(jī)械的表面強(qiáng)化。在實(shí)際的工業(yè)生產(chǎn)中，為了兼顧Ni-P膜層的鍍膜速率、物理和化學(xué)等綜合性能，往往在鍍液中添加多種組分，比如第二主鹽、添加劑、納米無機(jī)鹽顆粒。有些還對(duì)所得的Ni-P膜層進(jìn)行熱處理，以上的改善方式使鍍液成分變得復(fù)雜，使生產(chǎn)和后處理成本提高。本論文以熱軋態(tài)AZ31鎂合金為研究對(duì)象，利用化學(xué)鍍法在其表面沉積Ni-P膜層。通過在鍍液中添加不同濃度的添加劑，研究其對(duì)化學(xué)鍍Ni-P膜層的耐蝕性、顯微硬度、干摩擦系數(shù)等力學(xué)性能的影響。用X射線粉末衍射儀(XRD)、掃描電子顯微鏡(SEM)、能譜分析(EDS)、顯微硬度儀、高溫圓盤磨損儀、電化學(xué)工作站等儀器對(duì)所沉積的Ni-P膜層的成分、形貌、晶粒尺寸，，膜層硬度，耐磨性及耐蝕性能進(jìn)行了表征分析。得到的結(jié)論如下： (1)當(dāng)糖精鈉的濃度從0g/L增加到5g/L，SEM顯示所得Ni-P膜層的晶粒尺寸和膜層的厚度是逐漸減少的，孔隙的數(shù)量是先減少后增加；EDS數(shù)據(jù)顯示磷的含量也是逐漸降低的(其含量都大于7wt.%，屬于高磷膜層)。極化曲線及阻抗圖譜顯示2g/L糖精鈉的鍍液中所得膜層在3.5%NaCl溶液的耐腐蝕性最好。并對(duì)2g/L糖精鈉濃度的鍍液中所沉積的Ni-P膜層的形成機(jī)理做了詳細(xì)的研究，發(fā)現(xiàn)其由兩步反應(yīng)組成：第一步是Ni離子與鎂合金基體之間的置換反應(yīng)，第二步是鎳與磷的共沉積反應(yīng)。顯微硬度數(shù)據(jù)發(fā)現(xiàn)Ni-P膜層硬度隨糖精鈉的濃度增加呈現(xiàn)一個(gè)上升的趨勢(shì)。當(dāng)糖精鈉的濃度為5g/L，膜層的顯微硬度值達(dá)到1003.7HV0.025。Ni-P膜層與不同的摩擦副摩擦體現(xiàn)出不同的摩擦機(jī)理：與GCrl5摩擦副摩擦表現(xiàn)為輕微切削磨損機(jī)理；與Al2O3摩擦副摩擦表現(xiàn)出粘著磨損機(jī)理。而且膜層通過與不同摩擦副的磨損實(shí)驗(yàn)顯示：Ni-P磨層的失重、磨痕的寬度及摩擦系數(shù)隨糖精鈉的濃度增加而變小,說明隨著鍍液中糖精鈉濃度的增加Ni-P膜層耐磨性是逐漸增加的。 (2)當(dāng)聚乙烯吡咯烷酮(PVP)的濃度從8g/L增加到12g/L，XRD和EDS數(shù)據(jù)顯示膜層由結(jié)晶性較好的Ni單晶和結(jié)晶性差的Ni-P組成。SEM顯示所得Ni-P膜層的厚度是增加后減少。極化曲線及阻抗圖譜顯示10g/L聚乙烯吡咯烷酮的鍍液中所得Ni-P膜層在3.5%NaCl溶液的耐腐蝕性最好。極化曲線有個(gè)極小的自腐蝕電流密度(1.29μA/cm2)和高的極化電阻(73581Ωcm2)，說明此膜層展現(xiàn)較好的耐蝕性。
[Abstract]:The electroless plating shows advantages in uniformity, corrosion resistance, hardness, solderability, magnetism and decoration. As an excellent surface treatment technology, it has been widely used in many fields, such as military equipment, mold, aviation, textile, food and wood processing machinery surface strengthening. In practical industrial production, in order to take account of the coating rate, physical and chemical properties of Ni-P film, many components such as second main salt, additive and nano-inorganic salt particles are often added to the bath. Some of the obtained Ni-P films are heat-treated, and the above improvements make the composition of the bath become more complicated, and the production and post-treatment costs are increased. In this paper, hot rolled AZ31 magnesium alloy was used to deposit Ni-P film on its surface by electroless plating. The effects of additives of different concentrations on the corrosion resistance, microhardness and dry friction coefficient of electroless Ni-P coating were studied. X-ray powder diffractometer (XRD),) scanning electron microscope (SEM),) was used to analyze the composition, morphology and grain size of Ni-P film deposited by (EDS), microhardness tester, high temperature disc wear tester and electrochemical workstation. The hardness, wear resistance and corrosion resistance of the film were characterized and analyzed. The conclusions are as follows: (1) when the concentration of sodium saccharin increases from 0g/L to 5 g / L SEM, the grain size and thickness of the Ni-P film decrease gradually, and the number of pores decreases first and then increases; The EDS data showed that the phosphorus content decreased gradually (the contents were higher than 7 wt. and belong to the high phosphorus film). Polarization curves and impedance spectra showed that the coating obtained in the solution of 2g/L saccharin sodium had the best corrosion resistance in 3.5%NaCl solution. The formation mechanism of the Ni-P film deposited in the bath of 2g/L saccharin sodium concentration was studied in detail. It was found that the formation mechanism of the Ni-P film was composed of two steps: the first step was the replacement reaction between Ni ion and magnesium alloy substrate. The second step is the codeposition of nickel and phosphorus. Microhardness data show that the hardness of Ni-P film increases with the concentration of saccharin sodium. When the concentration of sodium saccharin is 5 g / L, the microhardness of the film reaches to different friction mechanism of 1003.7HV0.025.Ni-P film and different friction pairs. The friction mechanism of GCrl5 friction pair is slight cutting wear mechanism. Friction with Al2O3 friction pair shows adhesive wear mechanism. Moreover, the wear experiments with different friction pairs showed that the weight loss, wear mark width and friction coefficient of Ni-P wear layer decreased with the increase of saccharin sodium concentration. The results show that the wear resistance of Ni-P film increases with the increase of concentration of saccharin sodium in the plating solution. (2) when the concentration of polyvinylpyrrolidone (PVP) increased from 8g/L to 12 g / L, XRD and EDS data show that the film is composed of Ni single crystal with good crystallinity and Ni-P with poor crystallinity. SEM shows that the thickness of Ni-P film increases and then decreases. Polarization curves and impedance spectra showed that the Ni-P film obtained from 10g/L polyvinylpyrrolidone plating solution had the best corrosion resistance in 3.5%NaCl solution. The polarization curve has a minimal corrosion current density (1.29 渭 A/cm2) and a high polarization resistance (73581 惟 cm2), which indicates that the film exhibits good corrosion resistance.
【學(xué)位授予單位】：太原理工大學(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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