【作者】 于金库；

【导师】 荆天辅； 王明智；

【作者基本信息】 燕山大学 ， 材料学， 2009， 博士

【摘要】 本文以实现在结晶器基体铜或铜合金上镀覆耐磨Ni-Fe合金镀层为目的。在对国内外结晶器表面镀覆技术研究现状进行深入分析的基础上,对Ni-Fe合金镀层制备中的工艺技术进行了研究。采用普通电沉积法和喷射电沉积法在铜或铜合金基体上镀覆了Ni-Fe合金镀层,然后将镀层连同基体一起在400℃下进行去氢处理,以保证镀层和基体之间具有良好的结合强度。在镀覆Ni-Fe合金的过程中,研究了电解液成分和工艺参数对Ni-Fe合金镀层组织和性能的影响;在喷射电沉积Ni-Fe合金的过程中,研究了喷射速度和电流密度对Ni-Fe合金镀层组织和性能的影响。通过调整镀液中Fe2+、Ni2+的浓度,可以获得不同铁含量的Ni-Fe合金镀层。运用X射线衍射的θ-2θ扫描对Ni-Fe合金镀层的相组成进行了分析;采用SEM和EDS分别对Ni-Fe合金镀层的表面形貌和成分进行了分析;采用MMU-5G型屏显式端面摩擦磨损试验机对Ni-Fe合金镀层的耐磨性进行了分析;采用DIL 402C热膨胀仪对Ni-Fe合金镀层的热膨胀系数进行了测定;采用STA 449 C/6G综合热分析仪对Ni-Fe合金镀层的高温氧化性能、过冷及结晶过程进行了分析。研究结果表明,利用孔隙适合的多孔材料处理铁阳极,添加自己合成的YD-JK添加剂,在适合的工艺条件下,可以获得晶粒尺寸在20 nm以下、镀层厚度2 mm以上的Ni-Fe合金镀层,镀层的耐磨性是相同厚度Ni镀层的2~3倍,改变镀液中浓度比,获得了铁含量为3~5 wt.%的纳米晶γ相Ni-Fe合金镀层;在喷射电沉积过程中,通过改变喷射速度和电流密度,可以获得铁含量3.54~5.02 wt.%,晶粒尺寸在10 nm以下的γ相纳米晶Ni-Fe合金镀层,沉积速率可达到7.0μm·min-1,电流效率可达到80 %,镀层显微硬度可以达到HV 565。热分析结果表明,Ni镀层熔体的最大过冷度为411 K,Ni-Fe合金镀层熔体的最大过冷度为426 K;过热度一定时,Ni镀层熔体和Ni-Fe合金镀层熔体的过冷度都随冷却速率的提高而增大,冷却速率越高,试样完全结晶所需时间越短;在冷却速率一定的情况下,在一定的温度范围内,可以通过增大过热度来实现Ni镀层熔体和Ni-Fe合金镀层熔体的深过冷。更多还原

【Abstract】 The purpose of this dissertation, is to obtain excellent wear-resistance Ni-Fe alloy coating on the crystallizer bases: copper or copper alloys. With the extensive survey of the reported references of the coating technology on crystallizer surfaces, the preparation technology of Ni-Fe coating is intensively discussed.The conventional electrodepositing methods and jet electrodepositing methods are used to prepare the alloy coating on the copper substrate or copper alloys substrate. The coating with the substrate was then processed with de-hydrogenization at 400 centigrade to obtain the desirable binding strength between the coating and the substrate.For the coated Ni-Fe alloy, the effects of the electrolyte composition and the process parameters on the structure and properties of the coating are discussed, while for the jet eletrodeposited alloy coating, the effects of the jet rate and the current density are highlighted.The phases in the Ni-Fe coating are identified with X-ray diffraction, and SEM and EDS are used to determine the surface morphology and composition. The wear-resistance property is examined in a MPW wear test machine. The thermal expansion coefficient is determined by using a DIL 402C dilatometer, and the STA 449 C/6G analyzer is used to analyze the undercooling and crystallization processes as well as the oxidation behavior at high temperature.The results suggest that the desirable composition in this dissertation and certain processing technology together with the synthesized YD-JK additive facilitate the formation of a 2 mm thickness of Ni-Fe coating with grain sizes smaller than 20nm, whose wear-resistance is 2~3 times higher than that of the Ni coating of the same thickness. The adjustment of ratio of Fe2+/Ni2+ in the eletrolytes helps to obtain theγ-nanocrystalline containing Ni-Fe coating with 3~5% iron. The change of spray rate and current density helps to obtain theγ-nanocrystalline (grain size being smaller than 10nm) containing Ni-Fe coating with 3.54~5.02 wt % iron, and the deposition rate can reach 7.0μm·min-1 with the current efficiency being up to 80%, and the microhardness of the coating reaches HV 565. The thermal analyses suggest that while the Ni coating melt holds an undercooling degree of 411K, the Ni-Fe alloy coating melt has a value of 426K. With the superheating degree fixed, the undercooling degree of Ni and Ni-Fe coating melts rises with the cooling rates. The higher cooling rate leads to a shorter crystallization time. In parallel, with the cooling rate fixed, the deep undercooling can be reached in a certain temperature range by enhancing the superheating degree.更多还原