GOALI: Platinum-Enriched Gamma + Gamma Prime Bond Coats for Next-Generation Single-Crystal Superalloys

技术：单相(镍，铂)铝涂层是公认的工业标准，作为最先进的热障涂层(TBC)系统的粘结层，可保护高温合金免受高温氧化。这种涂层在应用于难熔元素含量增加的单晶高温合金(例如，第三代和潜在的第四代高温合金)时面临着挑战，这是因为在粘结层/高温合金界面附近形成了脆性的拓扑紧密堆积(TCP)相和二次反应区(SRZ)。田纳西理工大学(TTU)和通用电气飞机发动机(GEAE)的这项合作，以及橡树岭国家实验室(ORNL)的参与，探索了一种新的粘合涂层系统。与(Ni，Pt)Al粘结涂层相比，新型富铂伽马优质两相粘结涂层具有更高的蠕变强度、更好的涂层与高温合金基体的相容性、提高了冶金稳定性、降低了制造成本。本研究的重点是(1)通过在成分控制良好的铸造模型合金上合成伽马-伽马优质涂层，阐明高温合金基材中的合金元素对涂层氧化性能的影响；(2)阐明涂层中的铂对抵消高温合金基材中某些难熔元素的不利影响的作用；(3)评估这种新的粘结涂层系统的长期稳定性，以考虑与基材的相互扩散和组织的演变。GEAE将提供铸造模型合金和涂层的总体设计指南，并将提供单晶高温合金材料和TBC涂层。将为GEAE的镍基高温合金确定具有最佳成分和微观结构的定制粘结涂层，重点是新一代单晶。涂层合金的性能将通过TTU和ORNL的实验室氧化测试以及GEAE设施的模拟发动机环境测试进行评估。非技术性：本研究不仅将为下一代单晶高温合金提供新的粘结涂层候选材料，还将为未来高温合金和热障涂层系统的设计提供依据。该项目允许PI，一位TTU的年轻女性教员，进一步研究高温涂料领域。这项目标研究的一个重要方面是为本科生和研究生提供在学术/行业团队环境中进行研究的机会。在GEAE的短期访问将帮助学生认识到材料设计/制造方面的真正工业挑战，并为他们未来的职业生涯做好更好的准备。将鼓励女学生参与该项目，并将招募一名女博士生参与该项目。通过TTU和当地女性工程师协会最近发起的一项名为“设计未来”的外联计划，PI计划通过一个实践学习研讨会，向田纳西州中部5-8年级的女孩们介绍奇妙的材料世界，以培养科学好奇心。由于材料加工已被列为该大学的主要研究领域，将为进行这项研究购买一台熔弧机，这将适时地增加TTU的整个材料研究设施。这项研究将与领先的工业公司和国家实验室建立长期的研究合作，从而提高田纳西州唯一的专门技术大学TTU的研究质量和能力。

TECHNICAL: The single-phase beta (Ni,Pt)Al coating is an accepted industrial standard as the bond coat in state-of-the-art thermal barrier coating (TBC) systems that protect superalloys against high-temperature oxidation. This coating faces challenges when applied to single crystal superalloys with increased content of refractory elements (e.g., the 3rd-generation and potential 4th-generation superalloys) due to formation of brittle topologically close-packed (TCP) phases and formation of a secondary reaction zone (SRZ) near the bond coat/superalloy interface. This GOALI collaborative effort between Tennessee Technological University (TTU) and General Electric Aircraft Engines (GEAE), with additional participation from Oak Ridge National Laboratory (ORNL), explores a new bond coat system. Compared to the (Ni,Pt)Al bond coat, the new Pt-enriched gamma-gamma prime, two-phase bond coat offers the advantages of a higher creep strength, better compatibility between the coating and superalloy substrate, improved metallurgical stability, and reduced manufacturing cost. This research focuses on (1) elucidating the effect of alloying elements in superalloy substrates on coating oxidation performance through synthesis of the gamma-gamma prime coatings on cast model alloys with well-controlled compositions; (2) clarifying the effect of Pt in the coating on counteracting detrimental effects of some refractory elements from the superalloy substrate; (3) assessing the long-term stability of this new bond coat system to account for interdiffusion with the substrate and evolution of the microstructure. GEAE will provide overall design guidelines for both cast model alloys and coatings and will supply single-crystal superalloy materials and TBC coatings. Custom-designed bond coats with optimal composition and microstructure will be identified for GEAE's Ni-base superalloys with the emphasis on newer-generation single crystals. The performance of the coated alloys will be evaluated by laboratory oxidation tests at TTU and ORNL, as well as tests in simulated engine environments at GEAE's facilities. NONTECHNICAL: This research will not only offer new bond coat candidates for the next-generation single-crystal superalloys but also provide a basis for the design of future superalloys and TBC systems. The project allows the PI, a young female faculty member at TTU, to further her research in the field of high-temperature coatings. An important aspect of this GOALI research is to provide the opportunity for undergraduate and graduate students to perform research in an academic/industry team environment. Short-term visits at GEAE will help students appreciate real industrial challenges in materials design/fabrication and better prepare them for future careers. Female students will be encouraged to participate and one female Ph.D. student will be recruited to work on the project. Through an outreach program, "Engineering a Future", recently initiated by TTU and the local Society of Women Engineers, the PI plans to introduce the wonderful world of materials to the girls in 5th-8th grades across the Mid-Tennessee via a hands-on learning workshop to foster scientific curiosity. An arc melter, to be acquired for conducting the research, will be a timely addition to the overall materials research facility at TTU, as materials processing has been listed as a thrust research area of the university. The research will build long-term research collaborations with leading industrial companies and national laboratories, thus enhancing the research quality and capability of TTU, the only dedicated technological university in the State of Tennessee.