STTR Phase I: Nano-Layered Composites as High-Temperature Hard Coatings

这个第一阶段的小型企业技术转移(STTR)项目旨在研究纳米层状涂层的高温性能。选择了特定的材料系统，以优化关键性能，包括硬度、与硬质合金刀具的热膨胀匹配性、防止溶解到钢件中的稳定性和抗氧化性。纳米层中强烈的位错约束将导致比整体涂层更好的高温硬度保持性。对涂层的抗氧化性进行了评价。纳米层状涂层的稳定性将通过退火实验和随后的X射线衍射进行表征。人们对在一定温度范围内(RT到1100℃)都表现良好的刀具涂层有很高的兴趣，因为人们希望以更高的切割速度切割，并且在加工过程中使用冷却剂越来越引起环境的关注。然而，传统的涂层材料表现不佳，主要是因为它们的硬度随着温度的上升而迅速下降。该提出者最近开发了一种新的涂层，将许多交替的纳米级bcc金属层和岩盐结构的氮化物(如Mo/NbN)结合在一起。结果表明，纳米层积可显著提高材料的硬度。在高温下保持30 Gpa的硬度，为探索新的高温稳定涂层提供了机会。纳米涂层刀具有可能使干切削成为传统湿法切削的实用替代方法。此外，它们还可以通过允许更高的切割速度来提高我们加工的经济性。

This Phase I SmallBusiness Technology Transfer (STTR) project aims to investigate high-temperature properties of nano-layered coatings. A specific material system is chosen that optimizes key properties including hardness, thermal expansion match with cemented-carbide tools, stability against dissolution into steel workpieces, and oxidation resistance. The strong dislocation confinement in nano-layers will lead to better high-temperature hardness retention than in monolithic coatings. The oxidation resistance of the coatings will be evaluated. The stability of the nano-layered coatings will be investigated through annealing experiments with subsequent characterization by x-ray diffraction. There is a high level of interest in cutting-tool coatings that perform well over a range of temperatures (RT to 1100 C) because of the desire to cut at higher rates and increasing environmental concerns over the use of coolants during machining. However, traditional coating materials do not perform well, primarily because their hardnesses decrease rapidly as temperature rises. The proposer has recently developed a new class of coatings, combining many alternating nanometer-scale layers of BCC metals and rocksalt-structure nitrides, e.g. Mo/NbN. Results show that nano-layering provides substantial hardness enhancements. Hardnesses 30 GPa are maintained at high temperatures providing an opportunity to explore new high-temperature stable coatings. Nano-layer-coated cutting tools have the potential to make dry cutting a practical alternative to traditional wet cutting methods. In addition, they can improve we-machining economics by allowing higher cutting speeds.