冷喷涂前驱体-热等静压制备致密TiAl金属间化合物

Preparation of Dense TiAl Intermetallics by Cold Spraying Precursor-Hot Isostatic Pressing

摘要:

TiAl基合金作为一种可替代传统高温镍基合金的高温轻质材料，因优异特性被作为高推重比先进军用飞机发动机高压压气机及低压涡轮叶片的首选材料，可在高温环境下长期服役。然而，TiAl基合金的传统制备方法如精密铸造、铸锭冶金、粉末冶金、激光增材技术等，均存在成品性能差、加工难度大、工艺复杂和成本高等问题。为克服这些问题，高效制备满足新一代航空发动机轻量化、耐高温服役需求的优异性能TiAl基合金，基于元素粉末冶金法，提出了一种新的制备方法。选用Ti和Al混合粉末，采用冷喷涂法制备TiAl基合金预制体，再结合热等静压烧结技术实现TiAl基合金的复合制备。同时，探究了沉积参数对沉积效率和TiAl基合金涂层成分的影响，研究了不同热等静压参数对TiAl基合金的组织性能的调控作用。结果表明，所制备的TiAl基合金涂层致密无明显缺陷，在压力为5 MPa和温度为500 ℃的冷喷涂工艺参数下，获得了75%的较高的沉积效率和4%的较小的涂层成分偏差。通过合理调控后续热等静压工艺的温度、压力和升温升压方式等参数，最终实现了组织致密的TiAl基合金制备。该复合制备新方法，避免了TiAl合金粉末本征脆性难以直接冷喷涂成形的缺点，充分发挥了冷喷涂和热等静压技术的优势，有效解决了传统 TiAl 合金成形难题，为冷喷涂-热等静压近净成形TiAl 基合金提供了参考。

Abstract:

TiAl-based alloys， as high-temperature lightweight materials capable of replacing traditional high-temperature nickel-based alloys， are favored for their superior properties in advanced military aircraft engines with high thrust-to-weight ratios， particularly in high-pressure compressor and low-pressure turbine blades applications where they can endure prolonged high-temperature service. However， current methods for preparing TiAl-based alloys， such as precision casting， ingot metallurgy， powder metallurgy and laser additive manufacturing technology， are plagued by issues such as poor finished product performance， challenging processing and molding， complex processes and high cost. In order to overcome these problems and efficiently produce TiAl-based alloys with excellent performance to meet the lightweight and high-temperature service requirements of next-generation aero-engines， this paper proposes a novel approach based on the element powder metallurgy. Initially， TiAl-based mechanical alloy precursors were prepared by cold spraying mixed Ti and Al powders， followed by composite preparation of TiAl-based alloys through hot isostatic pressing sintering. The article explores the effects of deposition parameters on deposition efficiency and coating composition， as well as the modulation of microstructure and properties of TiAl-based alloys by different hot isostatic pressing parameters. The results show that the prepared TiAl mechanical alloy coatings are dense and free of obvious defects， and high deposition efficiency （75%） and small deviation of coating composition （4%） are obtained under the spraying parameter of 5 MPa and 500 ℃. The TiAl-based alloy with dense microstructure can be finally prepared by reasonably regulating the parameters such as temperature， pressure， and heating and pressing mode of the subsequent hot isostatic pressing process. This new composite preparation method circumvents the challenge of intrinsic brittleness in TiAl alloy powder， which hampers direct cold spraying， while leveraging the strengths of both cold spraying and hot isostatic pressing. It effectively circumvents traditional TiAl alloy forming issues and provides a basis for near-net-shape forming of TiAl alloys using the cold spray additive manufacturing-hot isostatic pressing method.