AI 中文总结
本文首次成功制备了具有功能热机械性能和良好基体附着力的厚NiTi涂层（100-300微米），采用高速空气燃料热喷涂方法，并评估了其微观结构、相变和形状记忆行为。
AI 中文摘要
在工程部件表面沉积各种涂层以提高其耐磨、耐腐蚀、抗摩擦和热保护性能已成为标准做法。沉积金属NiTi形状记忆合金涂层可能是硬质陶瓷涂层的可行替代方案。NiTi涂层具有源于独特功能热机械性能的额外优势。然而，厚NiTi涂层的制备被证明是困难的。标准电镀和激光熔覆方法不适用于NiTi，最广泛使用的等离子喷涂方法倾向于产生化学不均匀且不发生马氏体相变的涂层，冷喷涂NiTi涂层与基体的附着力差。在这项工作中，我们首次成功制备了具有功能热机械性能且同时表现出良好基体附着力的厚NiTi涂层（100-300微米）。我们使用高速空气燃料热喷涂方法，采用四组不同的工艺参数在低碳钢上制备NiTi涂层。评估了NiTi涂层的化学成分、孔隙率、微观结构、相变和功能热机械性能。尽管涂层含有不均匀的微观结构、孔隙、氧化物颗粒、高密度位错缺陷和内应力，但它们在冷却和/或机械加载时发生马氏体相变。喷涂态的NiTi涂层需要退火以显示功能热机械性能。尽管其拉伸强度有限，但涂层在三点弯曲测试中表现出热驱动行为，并在纳米压痕和划痕测试中表现出形状记忆效应。
英文摘要
Depositing various coatings on surface of engineering components with the aim to improve their performance concerning wear, corrosion, friction and thermal protection is already a standard practice. Depositing metallic NiTi shape memory alloy coatings may be a viable alternative for hard ceramic coatings. NiTi coatings offer additional benefits originating from unique functional thermomechanical properties. However, fabrication of thick NiTi coatings turned out to be difficult. Standard electroplating and laser cladding methods are not suitable for NiTi the most widely used plasma spray methods tend to produce chemically inhomogeneous coatings that do not transform martensitically, cold sprayed NiTi coatings suffer from poor adhesion to the substrates. In this work we report on first ever successful fabrication of thick NiTi coatings (100-300 um) that display functional thermomechanical properties and simultaneously show very good adherence to the substrate. We used high velocity air fuel thermal spray method to fabricate NiTi coatings deposited on mild steel using four different sets of processing parameters. Chemical composition, porosity, microstructure, phase transformation and functional thermomechanical properties of the NiTi coatings were evaluated. Although the coatings contain inhomogeneous microstructure, voids, oxide particles, high density of dislocation defects and internal stress, they undergo martensitic transformation upon cooling and or mechanical loading. As sprayed NiTi coatings need to be annealed to display functional thermomechanical properties. Despite their limited tensile strength, the coatings displayed thermal actuation in 3 point bending tests and shape memory effects in nanoindentation and scratch tests.
Comments27 pages, 15 figures, 7 tables
