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

这项小型企业技术转移（STTR）第二阶段项目旨在开发用于高温摩擦学应用的新型纳米层状涂层，特别是在高温（高达1000摄氏度）下性能良好的切削工具涂层。由于希望以更高的速度切割，并且由于在加工过程中使用冷却剂增加了对环境的关注，因此对这些涂层有很高的兴趣。传统的涂层材料在这些条件下表现不佳，主要是因为它们的硬度随着温度的升高而迅速下降。第一阶段的研究开发了一种新型涂层，结合了许多纳米厚的金属和氮化物交替层，显示出明显的硬度增强。高温退火后的硬度保持在44千兆帕斯卡（GPa），证明了这些新材料作为高温稳定涂层的可行性。纳米层中的强位错约束可能比单片涂层产生更高的高温硬度，从而提高耐磨性。在第二阶段，将开发纳米层状涂层，优化关键性能，包括硬度，与基体的热膨胀匹配，抗溶解到不同工件的稳定性以及抗氧化性。纳米层涂刀具有潜力使干切削成为一种实用的选择，并改善湿加工性能。

This Small Business Technology Transfer (STTR) Phase II Project aims to develop novel nano-layered coatings for high-temperature tribological applications, specifically cutting-tool coatings that perform well at elevated temperatures (up to 1000 degrees C). There is a high level of interest in these coatings because of the desire to cut at higher rates and due to increasing environmental concerns over the use of coolants during machining. Traditional coating materials do not perform well under these conditions, primarily because their hardnesses decrease rapidly as temperature rises. Research in Phase I developed a new class of coatings, combining many alternating nanometer-thick layers of metals and nitrides, which show substantial hardness enhancements. Hardnesses up to 44 gigapascals (GPa) were maintained after high temperature annealing, demonstrating the feasibility of these new materials as high-temperature stable coatings. Strong dislocation confinement in nano-layers is likely to yield higher high-temperature hardness than in monolithic coatings, providing improved wear resistance. In Phase II, nano-layered coatings will be developed that optimize key properties including hardness, thermal expansion match with the substrate, stability against dissolution into different workpieces, and oxidation resistance. Nano-layered coated cutting tools have the potential to make dry-cutting a practical alternative, and to improve wet-machining performance.