等离子喷涂成型Mo/ZrC复合喷管的烧蚀性能研究

Ablation properties of Mo/ZrC composite nozzle fabricated by plasma spray forming

采用化学包覆法制备Mo-(10%) ZrC复合喷涂粉末,采用气氛保护等离子喷涂成形技术结合低压热等静压致密化技术制备内径为8 mm、壁厚16.5 mm、长30 mm的某实验型固体火箭发动机Mo/ZrC复合喷管,测试喷管在地面点火试车条件下的抗热震烧蚀性能。研究结果表明,气氛保护等离子喷涂成形Mo/ZrC复合喷管经1800℃、10 MPa处理60 min后,微细ZrC颗粒均匀分布,断口晶粒仅2～5μm,致密度达94.5%。经1800℃、10 MPa处理300 min后,Mo/ZrC复合喷管由层片结构转化为颗粒状结构,致密度提高至96.8%,显微硬度及拉伸强度分别达259.8 HV0.025及138.9 MPa。地面试车实验后,Mo/ZrC复合喷管整体结构完好,未出现炸裂和破碎现象,抗热震烧蚀性能良好,其线烧蚀率仅为0.18 mm/20 s。地面试车过程中,机械剥蚀、熔化烧蚀及热化学烧蚀等三种烧蚀机制同时发生,Mo/ZrC复合喷管烧蚀程度依次为喉部>收敛段>扩散段。

Molybdenum-10.0% zirconium carbide(Mo-10.0% ZrC) composite feedstock was fabricated by a chemical deposition method. Mo/ZrC composite nozzle(inner diameter of 8 mm,length of 30 mm and wall thickness of 16.5 mm) was produced by shrouded plasma spray forming(SPSF) followed by low pressure hot isostatic pressing(HIPing).The resistance of thermal shock and ablation property of Mo/ZrC composite nozzle was investigated by ablating test on a small solid rocket motor(SRM). After HIPing at 1800 ℃ and 10 MPa for 60 min,ZrC particles were evenly distributed in the deposits and molybdenum grains were fine(only 2 ~ 5 μm).Initial lamellar structure could be found in local regions of Mo/ZrC composite nozzle with relative to theoretical maximum density of about 94. 5%. After HIPing at 1800 ℃ and 10 MPa for 300 min,relative density of deposits with initial lamellar structure transforming into granular one was increased up to 96.8%.Micro-hardness and UTS of deposits were 259.8 HV0.025 and 138.9 MPa,respectively.After engine test,the specimen was integrated without cracks,which indicates that Mo/ZrC composite nozzle has good resistance to thermal shock and ablation.The line ablation rate of nozzle was only 0.18 mm/20 s. Three types of ablation mechanisms including mechanical erosion,thermophysical erosion,and thermochemical ablation took place during hot-firing test.The order of degree of ablation is as follows: nozzle throat>convergence>dilation inside Mo/ZrC composite nozzle.