双丝电弧喷涂Ni-Al涂层制备及性能研究

发布时间：2018-02-27 14:19

本文关键词： 双丝电弧喷涂 Ni-Al涂层 6061-T6铝合金显微结构力学性能　出处：《哈尔滨工业大学》2015年博士论文　论文类型：学位论文

【摘要】：本文根据大型船舶偏流板服役特点,研究了双丝电弧喷涂(TWAS)Ni-Al涂层制备及性能问题,并对TWAS过程进行了研究。利用VOF双相流模型和标准k-ε模型,分析了不同直径熔滴在不同雾化气体压力下的变形和破碎过程,以及Weber数对熔滴破碎过程的影响。同时对不同速度的熔滴撞击基体的变形和凝固温度场进行了详细分析,揭示了TWAS喷涂粒子速度的气体飞行动力学规律。基于不同类型的涂层制备方法和工艺、涂层结构和材料的耦合制备了多种结构涂层,明晰了不同的喷涂工艺参数与TWAS过程中喷涂粒子尺寸间的关系。在结合强度、摩擦系数及耐磨性初步分析基础上,对各种涂层结构进行了全面的性能分析,研究了显微硬度、结合强度、耐冲击、耐高温和耐腐蚀等特性与涂层结构的关系。对所获最优Ni-Al复合涂层的显微结构、表面粗糙度和耐磨性能进行了系统研究。分析了不同热处理工艺对Ni-Al涂层显微组织和相结构的影响,讨论了涂层与铝合金基体界面反应机理,以及基体和涂层之间的界面元素扩散行为。获得以下结果:采用双丝电弧喷涂和火焰喷涂在6061-T6铝合金基体上制备Ni-5wt.%Al、Ni-20wt.%Al、Ni-30wt.%Al单层结构、Ni-5wt.%Al//Ni-5wt.%Al、Ni-5wt.%Al//Ni-20wt.%Al、Ni-5wt.%Al(Arc)//Al包Al2O3(Arc)、Ni-5wt.%Al(Arc)//Al包Al2O3(Flame)双层结构、Ni-5wt.%Al//Zn//Ni-5wt.%Al、Ni-5wt.%Al//Zn//Ni-20wt.%Al三明治结构等九种不同结构涂层,根据结合强度、耐高温、耐冲蚀性、抗热冲击、抗加速腐蚀、化学溶液耐受性和盐雾腐蚀等性能进行对比分析,确定了金属基涂层的成分和结构,即以Ni-5wt.%Al为打底层和Ni-20wt.%Al作为面层的复合涂层结构。双丝电弧喷涂熔滴破碎形式为一次破碎和二次破碎形式及爆炸式破碎形式。Weber数与雾化气体压力呈近似线性关系。在一定范围内变化时,增大喷涂雾化空气压力可以提高熔滴飞行速度,改善熔滴雾化效果。熔滴的形态、凝固层变化和温度场变化一致,并获得了熔滴冷却速度范围为3.1×107~7.6×107K/s。TWAS喷涂粒子速度的气体飞行动力学计算和分析结果表明,TWAS喷涂粒子在雾化气体中的初始加速较快,然后趋于平缓和稳定。当喷涂粒子加速飞行距离为200mm,且粒子的粒度范围为5μm~50μm时,喷涂粒子的飞行速度仅能达到初始气流速度的15%~45%。Ni-5wt.%Al涂层中的主相为Ni固溶体,还包括少量Al2O3、Ni O和Ni3Al4;Ni-20wt.%Al涂层中的主要组成相为Ni固溶体、Ni Al和Ni3Al。TEM分析表明:在原始态Ni基体上形成细小的球形Ni3Al析出相,同时存在非晶相和等轴晶,均系喷涂粒子在极快的冷却过程中形成。经过电子探针能谱分析,涂层主要由Ni、Al和O等元素构成。Ni-Al涂层具有较高的结合强度、硬度、粗糙度和较大的静摩擦系数。Ni-20wt.%Al涂层表现出较好的耐磨性,200个循环磨损后,湿态静摩擦系数大于干态静摩擦系数,涂层在整个磨损过程中始终表现为粘着磨损。激光共聚焦显微镜分析结果表明:随着喷涂距离和喷涂空气压力减小,Ni-Al涂层的表面粗糙度增大,但随着喷涂距离的减小,喷涂空气压力影响减弱。Ni-Al涂层经400℃~550℃/4h~48h热处理后,相组成变化较小。根据Miedema理论模型,涂层/基体界面发生扩散,形成金属间化合物Ni Al3,随着热处理温度升高和时间的延长,在Ni Al3相和涂层之间形成Ni2Al3相,同时界面扩散区逐渐增厚,该过程由Al原子的扩散所控制。热处理后的TEM分析表明:涂层中存在Ni Al3、Ni2Al3及Ni的退火孪晶相。根据在400℃、480℃和550℃温度不同时间的小角衍射结果,Ni-Al合金扩散动力学符合3次方规律,根据S.Arrhenius公式,建立高温原子扩散模型,计算出晶粒的长大指数n值均在0.25~0.35之间,与理论推导关系x2∝t1-n一致。在特定工艺条件下,较高的喷涂压力易于产生较小的喷涂粒子,适合作为Ni-Al复合涂层的打底层,而相对较低的喷涂压力产生相对较大的喷涂粒子,更适合作为偏流板涂层的面层。
[Abstract]:According to the large ship drift plate serving features, the twin wire arc spraying (TWAS) preparation and properties of Ni-Al coating, and the process of TWAS was studied. K- model and standard k-e model for two phase flow using VOF, analyzes the different diameter of the droplet in different atomizing gas pressure under the process of deformation and breakup. And the influence of Weber number on the droplet breakup process. At the same time on different speed of droplets impinged on the substrate deformation and solidification temperature field are analyzed in detail, reveals the gas particle velocity flight dynamics TWAS. The method and technology of preparing coating based on a variety of different types, structure of coatings coating structure and coupling the relationship between spraying materials, particle size between the clarity of the different spraying parameters and TWAS process. In the preliminary analysis of bonding strength, friction coefficient and wear resistance on the basis of various coating structure A comprehensive performance analysis of microhardness, adhesion strength, impact resistance, high temperature resistance and the relationship between corrosion resistance and coating structure. To obtain the optimal Ni-Al microstructure of the composite coating, surface roughness and wear resistance were studied. Analysis of the effect of different heat treatment process and phase structure of Ni-Al the coating microstructure, interfacial reaction mechanism of coating and Aluminum Alloy is discussed, and the interface element between the coating and the substrate diffusion behavior. The following results were obtained: by double wire Ni-5wt.%Al was prepared in the 6061-T6 Aluminum Alloy base on arc spraying and flame spraying Ni-20wt.%Al, Ni-30wt.%Al, Ni-5wt.%Al//Ni-5wt.%Al, Ni-5wt.%Al//Ni-20wt.%Al, single layer structure, Ni-5wt.%Al (Arc) //Al Al2O3 (Arc), Ni-5wt.%Al (Arc) //Al Al2O3 (Flame) Ni-5wt.%Al//Zn//Ni-5wt.%Al, Ni-5wt.%Al double layer structure, //Zn//Ni-20wt.%Al sandwich structure etc. Nine different structures according to the coating, bonding strength, high temperature resistance, erosion resistance, thermal shock resistance, accelerated corrosion, comparative analysis of chemical solution resistance and salt fog corrosion, determine the composition and structure of coatings on metals, i.e. Ni-5wt.%Al layer and Ni-20wt.%Al as composite coating surface layer. Twin wire arc spraying droplet breakage form of a broken and two crushing forms and shattered form.Weber number and atomization pressure is approximately linear. Changes within a certain range, increasing the spray air pressure can increase the droplet flight speed, improve the droplet atomization effect. The droplet morphology, consistent the solidified layer changes and temperature changes, and obtained the droplet cooling speed range for the calculation and analysis results of gas dynamics flight 3.1 * 107~7.6 * 107K/s.TWAS particle velocity shows that the spray particles TWAS In the initial atomization gas in accelerating faster, and then slow and stable. When the spray particle acceleration flight distance is 200mm, and the particle size range is 5 m~50 m, 15%~45%.Ni-5wt.%Al coating particles flying speed can only reach the initial air velocity in the main phase of Ni solid solution, also includes a small amount Al2O3, Ni, O and Ni3Al4; mainly composed of Ni-20wt.%Al phase in the coating is Ni solid solution, Ni Al and Ni3Al.TEM analysis showed that the formation of fine spherical Ni3Al precipitates in the original state of the Ni matrix, and existence of amorphous and equiaxed crystal, were sprayed particles in the cooling process of fast formation. After EPMA analysis, the coating is mainly composed of Ni, Al and O combined with strength, the elements of.Ni-Al coating with high hardness, roughness and large coefficient of.Ni-20wt.%Al coating showed better wear resistance of static friction, 200 cycle wear, wet The static friction coefficient is larger than the state of dry friction coefficient in the coating wear process was adhesive wear. Laser confocal microscopy analysis showed that with the spraying distance and spraying air pressure decreases, the surface roughness of Ni-Al coatings increased, but with the spraying distance decreases, spraying air pressure effect of.Ni-Al coating was decreased 400 DEG ~550 DEG /4h~48h after heat treatment, the phase composition changed little. According to the theory of Miedema model, the coating / substrate interface diffusion, formation of intermetallic compound Ni Al3, with the increase of heat treatment temperature and time, Ni2Al3 phase is formed between Ni Al3 and coating, while the interface diffusion zone gradually thickening, the process control the diffusion of Al atoms. After heat treatment, TEM analysis showed that Ni Al3 coating, Ni2Al3 and Ni of the annealing twins. According to 400 degrees, 480 degrees and 550 degrees at the same time, the temperature is not small Angle diffraction results accord with the 3 power law of Ni-Al alloy diffusion dynamics, according to the S.Arrhenius formula, a high temperature atomic diffusion model, calculated the grain growth index n value was between 0.25~0.35, and the relationship between x2 / t1-n theory. Under specific conditions, high pressure spraying easy to spray particles with smaller, suitable for as a base layer of Ni-Al composite coating, and spraying pressure is relatively low to produce spray particles relatively large, more suitable for the surface layer drift plate coating.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG174.4

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