原位反应激光熔覆Ti3SiC2陶瓷基复合材料的微观组织调控及复合机理

Fabrication of high-temperature ceramic materials by laser direct manufacturing method, with a high application potential, has become an important research area. However, we meet great challenge and difficulty due to the high melting point and the great brittleness of most of ceramics and thus the poor fluidity during the laser cladding process. Ti3SiC2 ternary ceramic is known as damage-tolerant material or “ductile” ceramic. On this basis, in the present project, the method of fabrication of Ti3SiC2-based ceramic composite by in-situ reaction laser cladding is proposed, which is believed to be favorable to the solution to the poor fluidity problem of liquid ceramic appeared in the direct melting process of ceramic particles. The newly proposed method is expected to improve the forming quality of the laser cladded ceramic layer..The following scientific questions will be addressed: The laser cladding condition required for in-situ synthesis of Ti3SiC2 ceramic and related reaction principle, formation mechanism of multi-constituent phases when adding the high-temperature reinforcement and toughness reinforcement into the Ti3SiC2 ceramic, and the fracture mechanism of the fabricated Ti3SiC2-based ceramic composite..This project includes the main research contents as the follows: (1) In-situ reaction laser cladding experiment for Ti3SiC2 synthesis; (2) The influence of the united nodular particles on the forming quality of the laser cladded Ti3SiC2 ceramic and the microstructure; (3) The influence of the addition of SiC ceramic and Nb (Ta) metal paticles; (4) The microstructure control and formation mechanism; (5) Mechanical properties and fracture mechanism of the Ti3SiC2-based ceramic composites, as well as the oxidation resistance at elevated temperatures..The aim of this project is to acquire Ti3SiC2-based ceramic matrix composite without evident defect by the newly-proposed method, to control the microstructures of the fabricated ceramic composite and reveal the influence of different laser cladding condition and raw powder materials on the microstructures and the forming quality, and to clarify the fracture mechanism. The project is theoretically valuable in the field of additive manufacture.

激光直接制造法制备高温陶瓷是航空航天领域有发展前景的研究方向，但是大多数陶瓷熔点高、脆性大、液态流动性差，因此激光成形存在难点。项目提出粉末原位反应激光熔覆制备Ti3SiC2基陶瓷复合材料，避免了单纯直接熔化高熔点陶瓷引起的液态流动性差问题，而且Ti3SiC2陶瓷属于损伤容限性材料或“韧性”陶瓷，有利于提高激光成形质量。.研究的科学问题：激光熔覆原位合成Ti3SiC2的条件及反应原理、添加高温增强相和增韧相的多物相复合机理、材料断裂机理。.主要研究内容有：粉末原位反应生成Ti3SiC2的激光熔覆、复合球化粉末对成形质量和组织的影响、添加SiC和难熔金属Nb和Ta的影响、显微组织调控、室高温力学性能与断裂机理、高温抗氧化性能。.项目旨在通过新的途径获得无明显缺陷的Ti3SiC2基陶瓷复合材料，形成对微观组织结构进行调控的方法并揭示其中的规律，阐明陶瓷复合材料断裂机理。具有重要科学价值。

本项目按计划全面完成了计划的五项研究内容，具体包括：①混合粉末原位反应合成Ti3SiC2陶瓷的激光熔覆条件；②复合球化粉末对激光成形质量和微观组织的影响；③添加SiC陶瓷和难熔金属对微观组织的影响；④Ti3SiC2陶瓷基复合材料的显微组织调控；⑤室高温力学性能、断裂机理和高温抗氧化性能研究。.本项目按计划完成了三个科学问题的研究，包括①激光熔覆原位合成 Ti3SiC2陶瓷的条件和反应合成原理；②同时添加高温增强相和增韧相对合成 Ti3SiC2陶瓷反应的影响以及多种物相的复合机理；③复合材料的室高温力学性能及断裂机理。.本项目突破了原材料Ti-Si-C复合球化粉末制备、金属/陶瓷界面反应控制、复合材料中陶瓷增强相的分布及微观组织调控等关键技术。本项目提出了通过复合球化粉末，激光原位反应制备陶瓷基复合材料的技术途径，获得了陶瓷/金属的界面冶金结合与陶瓷颗粒分布的规律，揭示了激光原位反应过程中，陶瓷表层梯度界面层缓解陶瓷/金属界面应力的机理，实现了原位反应Ti3SiC2陶瓷基复合材料的激光增材制备。在激光形成的熔池中，Ti、Si、C元素原位反应生成了TiC、Ti3SiC2和Ti5Si3三种物相，TiC颗粒的尺寸约为几个微米，Ti3SiC2和Ti5Si3颗粒的平均尺寸均为100纳米左右。复合层中Ti3SiC2“韧性”陶瓷相的生成对控制增材制造过程中形成的裂纹起到很好的抑制作用，而细小的Ti5Si3和TiC反应产物则对复合层起到强化作用。通过韧性陶瓷的添加和微观组织分析，揭示出陶瓷复合材料的物相合成原理和成形机理；形成对微观组织结构进行调控的方法并阐明其中的规律。获得的复合材料在强度提高的同时，也有潜力进一步提高材料的承温能力。.本项目共发表 7 篇论文，其中 SCI 论文 5 篇(1篇为ESI高被引论文)、EI收录 2篇，出版编著1 部，申请专利 8 项。课题组成员以项目内容参加3次国际学术交流会议，并做学术报告。此外，项目执行过程中培养了博士研究生1名。1名参研人员晋升为研究员职称，2名参研人员晋升为高级工程师职称，另有1名参研人员入选2021年度中国科协青年人才托举工程，还有1名参研人员入选2020年度北京市科技新星。