摘要
为了改善航空航天用铝合金的耐磨性能,尤其是保证在使用环境温度升高情况下铝合金的正常使用。本文在机械球磨涂层与基体之间扩散层形成原理的基础之上,设计三维立体状扩散层来增大涂层与基体之间结合性能;采用融合机械球磨、激光织构微孔和电沉积3种技术的方法在铝合金表面制备贯穿式复合涂层,对复合涂层的力学和摩擦学性能进行测试分析研究。结果表明,电沉积Ni涂层完全覆盖了机械球磨涂层的织构表面,经过热处理后机械球磨涂层和电沉积涂层显微硬度分别约为285和165 HV,并且铝合金基体、机械球磨涂层和电沉积涂层3者界面处形成了三维立体结构扩散层。铝合金在室温情况下摩擦学性能表现正常,但在300 ℃下出现失效现象。针对4种复合涂层,室温下N150复合涂层的摩擦因数最低(约为0.7);300 ℃下N100、N150、N200复合涂层摩擦因数约为0.5。两种温度环境下4种样品的磨损率分布在(0.9~1.6)×1
在目前航空航天用材料减重的迫切需求下,铝合金材料的需求的扩大,进而苛刻环境下零部件所需的特殊性能也对铝合金材料提出了更高的要求。改善铝合金室温以及高温下的摩擦学性能,使其在宽温域环境中正常使用成为研究的重要工作之
表面涂层技术是提高材料表面防护性能的重要途径之一,机械球磨制备涂层技术和电沉积制备涂层技术均得到了广泛的研究。V. ZADOROZHNYY
机械球磨方法原理为固体与固体之间冷焊,有利于在铝合金表面制备高熔点复合涂层。铝合金表面强结合性涂层的制备是高性能铝合金的重要研究问题之一。本研究在机械球磨涂层与基体之间扩散层形成原理的基础之上,设计三维立体状扩散层来增大涂层与基体之间结合性能。首先在铝合金基体表面机械球磨制备Ni-Al复合涂层,然后对涂层进行激光织构打孔,最后在织构化表面电沉积Ni涂层。经过热处理后使得机械球磨涂层内部生成金属间化合物,并且铝合金基体、机械球磨涂层和电沉积涂层三者界面处形成三维立体状扩散层,最后对复合涂层的力学和摩擦学性能进行测试分析研究。
铝合金基体材料型号为ZL114A,外观尺寸约为12 mm×12 mm×3 mm;纯度为99%的Al粉,100~200目;纯度为99.9%的Ni粉,-200目;将Ni粉与Al粉混合机械球磨制备Ni-Al复合涂层(原子比为1∶1,粉末总质量20 g);研究采用400 r/min的转速旋转7 h,采用直径为6和8 mm的不锈钢球来提高其球磨能量,为了防止旋转过程中粉末温度上升,每球磨60 min时停止10 min。在机械球磨涂层表面进行织构化,直径分别为50、100、150和200 μm,深度约100 μm,圆间隔均为100 μm(分别命名为N50、N100、N150和N200)。电沉积制备Ni涂层120 min。电沉积溶液各成分浓度为:NiSO4·6H2O 240 g/L、NiCl2·6H2O 45 g/L、H3BO3 30 g/L、NaSO4 20 g/L。阴极电流密度为2.5 A/d

图1 实验过程示意图
Fig.1 Schematic diagram of test process
样品物相使用X射线衍射仪(型号:Bruker-AXS D8 Advance)进行测定;涂层硬度使用显微硬度仪(型号:HXS 1000A)进行测试,载荷0.2 kg,加载时间10 s;样品微观形貌和元素分布使用场发射扫描电镜(型号:Quant 250FEG)进行分析测试。样品的摩擦学性能采用高温摩擦磨损试验机(型号:HT-1000)进行测试,摩擦对偶球为直径6 mm的Si3N4陶瓷球,摩擦载荷500 g,滑动速度0.15 m/s,测试时间20 min,测试温度为室温和300 ℃。材料的磨损体积通过V=AL计算(V代表磨损体积,A代表磨斑横截面积,L代表磨斑直径),磨损率W通过W=V/SN计算(S代表滑动距离,N代表外加载荷)。

图2 样品表面X射线衍射图
Fig. 2 X-ray diffraction pattern of the sample surface

图3 4种涂层截面和面分布图
Fig.3 Cross-section microstructures and the elements distribution of four kinds of composite coatings

图4 复合涂层硬度
Fig.4 Hardness of composite coatings

(a) 室温

(b) 300℃
图5 4种涂层的室温和300 ℃摩擦曲线
Fig. 5 Friction coefficients of four kinds of samples at RT and 300 ℃

图6 4种样品在室温和300 ℃下的磨损率图
Fig. 6 Wear rate of four kinds of samples at RT and 300 ℃
由

图7 4种样品室温和300 ℃下的磨斑表面
Fig.7 Wear surface of four kinds of samples at RT and 300 ℃
(1)融合机械球磨、激光织构打孔和电沉积技术在铝合金表面制备了贯穿式结构的复合涂层。该结构涂层的制备对铝合金表面制备强结合性复合涂层具有重要参考价值。
(2)经过热处理后铝合金基体、机械球磨涂层和电沉积填充微孔三者界面处出现明显的三维立体式结构扩散层。
(3)复合涂层的制备降低了表面的磨损率,并且把铝合金的使用温度范围扩展到了300 ℃。
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