【作者】 耿伟；

【导师】 何继宁；

【作者基本信息】 河北工业大学 ， 材料学， 2006， 硕士

【摘要】 本文通过机械团聚法将Fe₂O₃和Al粉制备成适于等离子喷涂的复合粉体。并利用等离子反应喷涂的方法制备出了具有部分纳米结构的复合涂层。对复合涂层的显微形貌、微观组织、断裂韧性、耐磨性能等进行了检测和分析,同时对其反应机理进行了研究。 将微米级原始粉体（Fe₂O₃和Al）经过配比、混合、机械团聚、筛分等一系列过程,制备出了流动性好,尺寸分窄,形状规则的复合粉体。 将复合粉体送入等离子焰流,在焰流中被引燃并发生反应,反应产物借助高速的等离子焰流,在基体表面紧密堆积形成复合涂层;涂层主要以FeAl₂O₄与γ-Al₂O₃为层状组织,α-Fe颗粒弥散分布于涂层的层间或层内;TEM分析表明:FeAl₂O₄相主要以部分纳米等轴状晶或层片状晶的形式存在,而γ-Al₂O₃相和α-Fe相则以部分球形纳米晶存在。 通过对复合涂层与普通氧化铝涂层的压痕及断口形貌比较得出:复合涂层的压痕形貌更清晰,边缘没有出现塌陷和翘边现象;复合涂层断口存在较大起伏,特别是具有部分金属拔出机制的明显韧性断裂特征。从而定性地得出复合涂层具有良好的韧性。 在以Ni包Al为底层的情况下,复合涂层的结合强度要比普通AT13陶瓷涂层高约1/4;在没有底层时也要明显高于AT13陶瓷涂层。同时复合涂层的孔隙率也要比普通AT13陶瓷涂层低约1/2。 在相同油润滑条件下复合涂层的耐磨性明显优于AT13陶瓷涂层。复合涂层在低载荷下处于部分润滑或边界润滑状态,在高载荷下涂层由开始时的边界磨损,转变成混合磨损甚至是干料磨损,涂层磨损表面产生微裂纹。由于复合涂层具有极薄且致密的层状组织,同时有金属Fe颗粒的弥散分布,提高了涂层的韧性,从而使复合涂层具有较好耐磨性。 通过热力学计算、差热分析、反应产物的熔化及沉积状态的分析表明:复合粉体在等离子焰流中一旦发生反应,就立即开始分步进行;且在飞行过程中复合粉体就已反应完全,其反应产物以熔融态液滴形式溅射到基体上,最终形成以FeAl₂O₄和Fe为主要相,Al₂O₃相和少量FeO相存在的层状复合涂层。更多还原

【Abstract】 In this paper, composite powders of Al/Fe₂O₃ were fabricated by mechanical glomeration with Al and Fe₂O₃ powders, the composite coating can be obtained with part nanophase structure by reactive plasma spraying. The micro-pattern, microstructure, fracture toughness property and wear resistance of the coating were tested and analyzed. Meanwhile, the reaction mechanics was studied.Fe₂O₃-Al composite powders were prepared using iron oxide （Fe₂O₃） powders and aluminum powders by mechanical agglomeration technique. After being mixed in a ratio and agglomerated and sieved, the Al and Fe₂O₃ powders were made into composite powders for plasma spraying, with excellent liquidity, narrow distribution and well-regularity.The composite powders were fired and reacted when they were sent into plasma flame, the molten reactants, with the help of the high-speed plasma flame, impacted with the substrate to form this composite coating. SEM and XRD were carried out to determine the microstructure composition. Experiment results showed that the composite coating consisted of stratified matrix phase FeAl₂O₄ and phase Y-Al₂O₃, and spherical phase a-Fe was dispersedly embedded in the interlamination coatings. TEM analyses indicated that FeAl₂O₄ phase was composed of equiaxed crystals and layered crystal mainly, whilst γ-Al₂O₃ and a-Fe phases were composed of spherical crystals, which were nano-scaled partially.Comparisons were made between the composite coating and conventional Al₂O₃ coating on indentation and fracture to compare their tough properties. Indentation of the composite coating was more distinct, without collapsed and buckle structures, which were found around the indention of Al₂O₃ coating. In addition, some gliding fracture properties such as fluctuations and distinct pull-out mechanism were noticed on the composite coating fracture, while Al₂O₃ coating had brittle fracture properties only. So it was concluded that this composite coating had superior toughness, as compared with Al₂O₃ coating. These dispersed particles Fe contributed to its enhanced toughness.The composite coating had enough bond strength, which was almost 1.25 times of AT13 ceramic coating with Al/Ni base coating, and without base coating, the composite coating was apparently higher than AT13 ceramic coating. At same time, the porosity of AT13 ceramic coating was almost 1.5 times of the composite coating.The wear-resistance of this composite coating was much better than that of AT13 ceramiccoating under oil lubricated condition. In this paper, the abrasion mechanism was studied. Under low load, its mechanism was partial-lubricated abrasion or boundary-lubricated abrasion. However, under high load at first boundary wear was dominant. With the abrasive behaviors continuing, it turned to mixed wear even fatigue wear followed cracks initiation on the coating surface. During the whole process, these dispersed particles Fe and the lamellar structure, thin and dense enough, contributed to the enhancement of wear-resistance.Based on thermodynamics principles, DTA analyses and the conditions of reactants melt and deposited, the reaction process of the Fe2C>3-AI composite powders injected into the jet was investigated. These analyses results showed that reactions between Fe2C>3 and Al were carried out step by step and finished before the react products sputtered on the substrate in molten condition. So that this lamellar composite coating was fabricated, with the main phases（FeAl2O4 and Fe）, as well as AI2O3 phases and some residue FeO phases.更多还原