基于增材制造技术的SiC陶瓷基复合材料涡轮叶片高温强韧化制造

Turbine blades are the core high-temperature components of aero-engine. Its material developing into SiC ceramics matrix composite (CMC) is an inevitable trend. The intracavity of the blades, the Si-CMC material and the complexity of the shape make the manufacturing a huge challenge. Based on the additive manufacturing technology, the resin shell and fiber holder of the blades are made; relying on the fiber holder, the fiber preform input into turbine blade is obtained by fiber weaving technology; the interface layer of fiber is produced by chemical vapor deposition; the SiC matrix is manufactured by the gelcasting and reaction infiltration. Therefore a new method of manufacturing SiC-CMC blades is put forward. The influence rules of the structural parameters of fiber preform on the high-temperature strength and toughness of the SiC-CMC blades is to be studied, and the physical nature of high-temperature strengthening and toughening is explored; the thermal stress distribution of interface layer of fiber is researched, the high temperature damage conditions and the failure mechanism of interfacial layer are revealed; the influence of the process conditions, the property of solid phase、pore structure in gelcasting on rheological property is studied, and the plugging law in the internal blade shell is discussed; The transformation mechanism of residual Si in reaction infiltration is researched, and the relationship between process、microstructure、high-temperature strength and toughness is explored to provide the theoretical basis for developing new manufacturing technology of high-temperature strengthening and toughening SiC-CMC blades.

涡轮叶片是航空发动机的核心高温部件，其材料向SiC陶瓷基复合材料（CMC）发展是必然趋势，叶片的内腔/SiC-CMC材料/外形的复杂性，使得其制造成为一个巨大的挑战。为此，基于增材制造技术，成形叶片的树脂型壳和纤维支架；依托纤维支架，采用纤维编织，制造植入叶片型壳的纤维预制体，通过化学气相沉积，制备纤维的界面层；借助凝胶注模和反应熔渗方法，制备SiC基体，由此提出一种制造SiC-CMC叶片的新途径。拟研究纤维预制体的结构参数对SiC-CMC叶片高温强韧性的影响规律，探明纤维高温强韧化的物理本质；研究纤维受力中界面层热应力分布规律，提出界面层高温损伤条件，揭示界面层的失效机理；研究凝胶注模中工艺条件、固相属性、孔隙结构多因素对浆料流变性的影响，探寻叶片型壳内部堵塞规律；研究反应熔渗中残留Si转化机制，查找工艺、组织、高温强韧性之间关系，为发展高温强韧化SiC-CMC叶片制造新技术提供理论依据。

基于该面上基金的资助，探讨了化学气相渗透过程工艺参数对渗透产物的影响规律，并确定最佳工艺来制备界面层；研究了树脂、水基SiC素坯制备及其精度控制方法；研究了陶瓷浆料在纤维预制体内的充型与计算；研究SiC陶瓷基复合材料力学性能与残硅控制，分析了基于光固化成型技术的凝胶注模制造涡轮叶片的工艺、组织结构和性能的关系。研究表明：（1）对纤维预制体表面制备SiC界面层，选择SiC纤维作为预制体材料，通过化学气相渗透CVI工艺作为界面层制备工艺，当氢气与三氯甲基硅烷（H2/MTS）流量比为10、沉积时间为4h、氢气流量为2000ml/min，渗透温度为1050℃时，可制备厚度约为1μm的SiC界面层。（2）树脂基陶瓷浆料纤维预制体充型，纤维预制体孔隙较小，陶瓷浆料固相越高粘度越大，进而浆料充型能力越差。实验验证了当陶瓷浆料从25vol%降至15vol%时，纤维预制体充型能力最好，纤维束间孔被完全充满。（3）模拟了水基陶瓷浆料叶片充型，模拟结果显示当粘度从0.8 Pa•s上升至1.2 Pa•s时，浆料内气泡无法及时排出，最终形成较大较深的宏观气孔裂纹。（4）优化浸渗剂配方，以硅锆合金代替硅单质作为浸渗剂，反应烧结获得SiC陶瓷基复合材料，其物相组织主要包括SiC、Si和ZrSi2。当浸渗剂中硅锆质量比为1:1时，烧结体的残硅含量为12.5vol%，相比于硅单质浸渗试样，残硅含量降低67.0%，1500℃时弯曲强度为20.5MPa。（5）连续SiCf/SiC复合材料中SiC纤维虽制备了界面层且纤维体积含量达到35vol%以上，但由于其内部孔隙较多其断裂韧性仅为5.53MPa.m1/2，室温弯曲强度仅为280±21MPa，1500℃弯曲强度为117±42MPa；连续Cf/SiC复合材料中碳纤维在反应烧结过程中硅化严重，未起到增韧效果其断裂韧性仅为4.68MPa.m1/2，然而由于致密度较高室温弯曲强度达到386±36MPa，1500℃弯曲强度为174±27MPa；Si/SiC复合材料其致密度最高，室温弯曲强度达到410±17MPa，然而基体内残硅较多，1500℃弯曲强度为下降到10MPa以下，并且由于无增韧相，断裂韧性仅为3.23 MPa.m1/2。