电阻缝焊法制备金属基陶瓷梯度涂层及其传热传质机理研究

Aluminum alloys are one of the best material to achieve lightweight of automobile due to the advantages of low density, light quality, good formability and recoverable. However, the poor wear resistance on aluminum alloys surface severely restrict its application in high power engine of automobile. In this project, resistance seam welding method will be used to preparing metal matrix ceramic gradient coating on the surface of aluminum alloy to improve its wear resistance. By studying the heat and mass transfer in melting, seepage and solidification behavior of the gradient coating, the formation mechanism of the gradient coating is revealed. The contents of the project are as follows: calculating the heat source and its distribution of the gradient coating; The two-dimensional heat transfer model of seepage behavior will be built by numerical simulation when considering action of capillary force and penetration resistance; Analyzing the forming process of molten pool on the surface of aluminum, melting behavior of iron powders and solidification characteristics of both; Exposing the mass transfer law of the molten metal on the basis of the two-dimensional heat transfer model; Revealing the interface mass transfer behavior of aluminum/iron and iron/ceramic. Studying the effect of different preparation process on the organization and performance of gradient coating and finally fabricating the high-performance metal matrix ceramic gradient coating on the surface of aluminum alloys. The results have great significance to further expand the application scope and improve the application level of aluminum alloy.

铝合金具有密度小、质量轻、成形加工性好、可重复回收利用等一系列优点，因此, 铝合金是未来汽车轻量化的主要材料之一。但是铝合金表面耐磨性差严重制约了其在汽车大功率发动机中的应用，本项目针对这一问题提出采用电阻缝焊法在铝合金表面制备金属基陶瓷耐磨梯度涂层的新技术。通过研究梯度涂层中熔化、渗流及凝固行为相关的传热传质等基础理论问题，揭示梯度涂层的形成机理。研究包括计算梯度涂层在初始阶段热源大小及分布；考虑毛细管力和渗透阻力的作用下，通过数值模拟初步建立电阻焊中熔融金属渗流行为的二维传热模型；分析瞬态下铝基体熔池形成过程、金属粉末的熔化行为和凝固特性；在建立传热模型的基础上，阐明熔融金属渗流传质规律；揭示铝/铁和铁/陶瓷的界面传质行为。再通过研究不同工艺过程下梯度涂层的组织和性能，最终制备高性能的金属基陶瓷梯度涂层。研究成果的应用将对进一步扩大铝合金的应用范围、提高铝合金的应用水平具有重要意义。

铝合金是未来汽车轻量化的主要材料之一，但是铝合金表面耐磨性差严重制约了其在汽车大功率发动机中的应用，本项目针对这一问题提出采用电阻缝焊法在铝合金表面制备铁基碳化钨耐磨梯度涂层新技术。重点研究了梯度涂层中熔化、渗流及凝固行为相关的传热传质等基础理论问题，揭示梯度涂层的形成机理。研究结果包括（1）采用理论计算与实验结合，得出电阻缝焊焊接参数与电阻热关系曲线图；（2）通过数值模拟并实验验证建立了熔融金属渗流行为的二维传热模型，可为梯度涂层的组织提供准确预测；(3) 研究了铁基粉末粒度对梯度涂层渗流行为的影响，调控上层与中间层铁基粉末粒径比在1:4可获得良好组织和性能的铁基陶瓷梯度涂层；(4) 研究梯度涂层的磨损机理发现，不同磨损方式对涂层磨损机理影响最大；（5）建立了复合涂层的失效模型，可准确预测金属基陶瓷复合梯度涂层的失效位置。(6) 进一步发现电阻缝焊具有脉冲电流处理效果，可在制备涂层时提高涂层中金属相的位错密度并进一步提高涂层性能；本项目发表 SCI 论文9篇, 分 别 发 表在 《Journal of Materials Processing Technology》, 《Surface & Coating technology》和《Materials Characterization》等，申请发明专利10项，授权5项；参加国际会议2次，国内会议7次；联合培养硕士研究生5名，与日本东北大学和九州工业大学合作发表SCI论文4篇。