预热保温对激光选区熔化SiC晶须增韧YSZ陶瓷复合材料微缺陷的影响

For aerospace and biomedical applications, ceramic matrix composites are the potential materials for 15-20 high thrust-weight ratio aircraft turbine engine components in hot end and advanced bio-ceramic implants. Carbide (SiC) toughened yttria stabilized zirconia (YSZ) ceramic matrix composite is investigated as the main starting material in the project, by high temperature preheating, heat preservation and selective laser melting process optimization, researchers will explore a selective laser melting ceramic process with less microscopic defects and low deformation. Research contents include: laser melting SiC whisker morphology, distribution and bonding interface, laser melting whisker toughening effect analysis for YSZ ceramics; near melting point preheating and heat preservation technology, reducing the SLM laser scanning energy input and temperature gradient, and its effect on the micro defects morphology and distribution; by the study on microstructure, internal defects, phase structure, mechanical properties and forming accuracy of SLM ceramic sample, the selective laser melting process of ceramic matrix composites will be optimized. In the project, by studying the effect of preheating temperature and heat preservation process on the micro defects during the selective laser melting SiC whisker enforced YSZ ceramic composite, researchers will conclude the micro defect control technology on the ceramic matrix composite selective laser melting process, resolve the basic common issues of laser additive manufacturing ceramic material, initially realize high density ceramic sample with selective laser melting process, and improve the applied material system of laser additive manufacturing technology.

针对航空航天和生物医疗领域，陶瓷基复合材料是15-20高推重比航空发动机涡轮热端部件和先进生物陶瓷植入体的潜在应用材料。以碳化硅(SiC)晶须增韧钇稳定氧化锆(YSZ)陶瓷粉末为研究对象，通过高温预热保温和激光选区熔化的工艺优化，探索研究少微观缺陷和低形变的陶瓷激光选区熔化工艺。研究内容包括：激光熔化SiC晶须的微观形态、分布和结合界面，分析激光熔化晶须对YSZ陶瓷的增韧效果；陶瓷粉末近熔点预热和保温工艺，降低SLM扫描激光能量输入和温度梯度，研究其对微缺陷形态和分布的影响；SLM陶瓷样品微观组织、内部缺陷、相结构、力学性能和成型精度的研究，优化陶瓷SLM工艺。本项目通过研究预热保温对SiC晶须增韧YSZ陶瓷复合材料激光选区熔化中微缺陷的影响,获得激光选区熔化陶瓷的缺陷控制方法，解决陶瓷增材制造的基础共性问题，初步实现高致密度陶瓷材料的直接激光选区熔化，完善增材制造技术的应用材料体系。

本项目以0.5-5 wt%含量的碳化硅(SiC)晶须增韧钇稳定氧化锆(YSZ)陶瓷粉末为研究对象，分析了SiC晶须复合YSZ陶瓷复合粉末的显微形态、分布和结合界面，分析了晶须的分散性、复合粉末流动性和激光加热时状态变化。开展500W-2000W激光定点预热和500℃电阻加热保温试验，开展激光选区熔化工艺优化试验，通过成形单道、单层和多层的显微组织观察，分析缺陷类型和成因，优化获得少裂纹低形变的激光选区熔化样品。研究不同预热温度对YSZ陶瓷成形微缺陷形态和分布的影响，获得了SLM陶瓷样品的微观组织、内部缺陷、相结构、力学性能和成形精度。研究结果表明：YSZ陶瓷材料的激光选区熔化直接成形相对致密度达到91%。SiC晶须的流动性和分散性限制了晶须添加量，晶须复合材料的SiC最大比例为0.5%，低含量晶须增韧效果不明显。激光加热SiC晶须后成为金属Si、游离态C和原始态的SiC晶须；激光定点预热温度可以达到2500℃，其可以有效降低层间贯穿长裂纹的产生和层间裂纹的有序性，500℃保温可以有效减少熔道中心的有序裂纹。