微射流冷喷增材制造工艺及其宏/微尺寸特性演化机理

Based on the thermal processing of melting-solidification, traditional Additive Manufacturing (AM) for metals suffers from serious deficiency in material properties, such as poor densification, high residual stress and low fatigue strengthen, which limits its application in the aerospace industry. As a typical cold processing, Cold Spraying (CS) preparing highly density coatings by high-speed powder jet without phase changes could be a solution to overcome the difficulties faced by thermal-based processes. However, the poor dimensional precision induced by the low resolution of the jet and the ineffective control of the deposition processing hinders the development of CS to be a manufacturing technology. To promote the development of shape-and-performance-controlling manufacturing technologies, a new process named Micro-jet Cold Spraying Additive Manufacturing (MCSAM) is proposed, and the systematic investigation is conducted as follows. A macro-structure-and-micro-jet trans-scale jetting mechanism is developed and a new nozzle based on Aerodynamic Focusing is designed to generate micro-size jets. The jetting-deposition integral numerical model is developed to study the evolution mechanism of macro/micro dimensional properties in MCSAM. Based on the process-precision mapping, control strategies of precision are explored for the manufacturing of typical macro/micro-scale structures. With the help of the investigation, the evolution mechanism of dimensional properties during material accumulation could be unveiled. Meanwhile, as an effort to solve precision problems of CS, the investigation is also expected to promote the development of an advanced technology to manufacture key parts in the aerospace industry.

传统金属增材制造工艺基于熔融-凝固的“热加工”原理，广泛存在致密性低、残余应力大、疲劳强度低等材料性能问题，在航空航天等高端领域的应用存在瓶颈。冷喷涂为典型“冷加工”技术，利用高速射流形成致密涂层，无需材料相变，可克服传统热基工艺的不足。然而，冷喷涂却因射流分辨率低和沉积过程控制不严等导致加工精度较低，向制造技术的发展存在困难。鉴于此，为发展高精度高性能增材制造技术，本申请提出微射流冷喷增材制造新工艺原理，探索宏观结构-微观射流的跨尺度射流产生新机制，设计微米级高速射流的多级气动汇聚喷嘴；建立喷射-沉积整体工艺仿真模型，研究冷喷增材工艺宏/微尺寸特性的演化机理；建立工艺参数-加工精度映射关系，探索典型宏/微结构的精度控制策略。本项目有助于增进对材料累加中尺寸特性演化机理的理解，有望解决冷喷工艺加工精度不足的问题，可推动航空航天等领域关键零部件制造技术的发展。

传统金属增材制造工艺基于熔融-凝固的“热加工”原理，广泛存在致密性低、残余应力大、疲劳强度低等材料性能问题，在航空航天等高端领域的应用存在瓶颈。冷喷涂为典型“冷加工”技术，利用高速射流形成致密涂层，无需材料相变，可克服传统热基工艺的不足。然而，冷喷涂却因射流分辨率低和沉积过程控制不严等导致加工精度较低，向制造技术的发展存在困难。鉴于此，为发展高精度高性能增材制造技术，需探索宏观结构-微观射流的跨尺度射流产生新机制，建立喷射-沉积整体工艺仿真模型和工艺参数-加工精度映射关系，研究冷喷增材工艺宏/微尺寸特性的演化机理。.项目在如下三个方面取得了创新性成果：1）提出多级汇聚-分流挡板的汇聚喷嘴结构方案，优化分析不同喷嘴参数对射流特性的影响规律，使得高速金属射流的最小分辨率达到200μm；2）建立了基于规则的冷喷全工艺模型，建立了工艺参数与沉积尺寸特性的映射关系，研究了扫描重叠率、入射粉末分布等对沉积尺寸特性的影响规律；3）提出了基于冷喷工艺的冷-热复合金属3D打印工艺，提高了现有金属3D打印的材料的致密度。经过三年的研究，项目取得了成果，培养博士研究生1名，硕士研究生1名，发表期刊研究论文5篇，参加国际会议1人次，申请发明专利4项（其中授权1项）。.本项目有助于增进对材料累加中尺寸特性演化机理的理解，有望解决冷喷工艺加工精度不足的问题，可推动航空航天等领域关键零部件制造技术的发展。

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