【作者】 曹向飙；

【导师】 王从曾；

【作者基本信息】 北京工业大学 ， 材料学， 2004， 硕士

【摘要】 本文采用激光熔覆的方法在 TiAl 金属间化合物基体上沉积耐高温涂层，分别选取 NiCoCrAlY、NiCoCrAlY+5%Al2O3 以及 NiCoCrAlY+20%Al进行熔覆。并且用金相、显微硬度、 X－射线衍射（ XRD）、扫描电镜（ SEM）和能谱（EDX）等分析手段，分别研究了涂层的组织结构及高温氧化行为。 工艺实验结果表明，用一定量的硝酸纤维素和 MCrAlY 合金粉末混合后，用丙酮调成糊状，涂覆于基材表面的方法，在后续的激光熔覆中能形成高质量的 McrAlY 抗氧化涂层。激光熔覆工艺参数为 900W 的输出功率和350mm/min 的扫描速度是实验优选的最佳工艺参数。 氧化实验结果表明，在 1000℃条件下氧化 100 小时后，NiCoCrAlY 和NiCoCrAlY+5%Al2O3 涂层表面形成了 TiO2、Al2O3 等的复合氧化膜，主要是 TiO2。而 NiCoCrAlY+20%Al 涂层表面的氧化膜则主要是 Al2O3膜。 氧 化 动 力 学 曲 线 表 明 ， 抗 氧 化 性 从 优 到 劣 的 次 序 是NiCoCrAlY+20%Al、NiCoCrAlY+5%Al2O3、NiCoCrAlY。分析表明，Al 的添加一方面使得晶粒细化，另一方面阻碍其它离子扩散。同时增加了涂层中对抗氧化起作用的 Al 离子储备。有利于形成比较致密的 Al2O3 膜，增强涂层抗氧化性。更多还原

【Abstract】 A Laser cladding deposition technique was performed to make (NiCoCrAlY)coating. This coat is expected to work as a High-temperature resist for TiAlintermetallic substrate. Metallographic analysis, microhardness, SEM, XRD wereused to find the appropriate Laser cladding parameters (power and scan velocity),the deposit morphology and the oxidation behavior of the coat. Study showed that a mixture of Pyroxylin and alloy powder and acetone，which was deposited on the substrate, can help to form a high performancecoating. About Laser cladding parameters, 900W in power and 350mm/min invelocity are relatively good. After 100 hours oxidation experiment at 1000℃，a mixed TiO2、Al2O3layer was formed at the top of (NiCoCrAlY) coating and (NiCoCrAlY+5%Al2O3)coating. However the layer on top of (NiCoCrAlY+20%Al) coating was mainlyAl2O3. The results of high temperature oxidation tests in air at 1000℃showed thatthe oxidation resistance of the laser cladding (NiCoCrAlY+20%Al) wassignificantly higher than that of (NiCoCrAlY+5%Al2O3) and (NiCoCrAlY)coatings. Analysis tells that to add Aluminum in the powder can help to form ahigh quality coating. The mechanisms of Al to improve oxidation resistance wereDiscussed. Al can fine the grain size of cladding coatings and hinder thediffusion of other ions. It can also increase the content of Al3+ in the coating.Which all ensure to form a high density Al2O3 layer on the substrate and topromote its oxidation resistance.更多还原