Dong Shaoming

Hot isostatic pressing of SiCSi3N4 composite with rare earth oxide additions

SiCSi3N4 composites with rare earth oxide additions have been prepared by glass encapsulated hot isostatic pressing at 1850 °C and 200 MPa pressure. Mechanical properties and microstructures of the sintered samples have been studied. It is shown that different molar ratios of La2O3 to Y2O3 and the total amount of La2O3 and Y2O3 additions can affect the mechanical properties significantly. With 3 wt% La2O3 + Y2O3 additions, lower La2O3Y2O3 molar ratio exhibits higher bending strength and median fracture toughness, but relatively lower Vickers hardness. For addition of 6 wt% La2O3 + Y2O3, the higher bending strength, Vickers hardness and fracture toughness correspond to a certain La2O3Y2O3 molar ratio of 1.5, 1.0 and 0.5, respectively. SEM observation shows that the SiC matrix composite with fine grain size and homogeneous microstructure can be obtained.

碳/碳-碳化硅复合材料的摩擦磨损行为与机理

以液相渗硅工艺为手段制备了C/C-SiC复合材料。分别采用MMW-1A与MM-1000型试验机对复合材料的摩擦磨损性能进行了研究。结果表明: 在实验室条件下, 当压力恒定在0.48 MPa时, 转速对复合材料的摩擦磨损的性能影响甚微, 摩擦系数为0.15~0.16, 且磨损率接近; 当转速恒定在0.3 m/s时, 不同压力条件下的摩擦系数相近, 为0.13~0.15, 但磨损率存在较大差异, 材料磨损以磨粒磨损为主。在近工况条件下, C/C-SiC复合材料的摩擦系数达到0.50, 磨损率达到5.95 mg/次, 摩擦曲线表现为典型的马鞍形曲线, 试验前期材料磨损主要表现为磨粒磨损, 试验后期为粘着磨损。以液相渗硅工艺为手段制备了C/C-SiC复合材料。分别采用MMW-1A与MM-1000型试验机对复合材料的摩擦磨损性能进行了研究。结果表明: 在实验室条件下, 当压力恒定在0.48 MPa时, 转速对复合材料的摩擦磨损的性能影响甚微, 摩擦系数为0.15~0.16, 且磨损率接近; 当转速恒定在0.3 m/s时, 不同压力条件下的摩擦系数相近, 为0.13~0.15, 但磨损率存在较大差异, 材料磨损以磨粒磨损为主。在近工况条件下, C/C-SiC复合材料的摩擦系数达到0.50, 磨损率达到5.95 mg/次, 摩擦曲线表现为典型的马鞍形曲线, 试验前期材料磨损主要表现为磨粒磨损, 试验后期为粘着磨损。

ZrB 2 -SiC超高温陶瓷涂层的抗烧蚀性能研究

为了提高C/C复合材料的抗氧化烧蚀性能, 采用浆料浸涂与原位反应复合工艺在材料表面制备了ZrB 2 -SiC超高温陶瓷涂层, 利用氧-丙烷火焰测试了涂层的抗烧蚀性能。结果表明: 采用复合工艺所制备的ZrB 2 -SiC超高温陶瓷涂层与基材具有较高的结合强度; 在氧-丙烷火焰冲刷条件下, 涂层具有良好的抗烧蚀性能, 涂层经1500℃下烧蚀600 s, ZrB 2 -SiC涂层无明显烧蚀, C/C复合材料保持完好。微观结构观察表明: 烧蚀测试后, 涂层中存在ZrO 2 和大量超高温陶瓷相, 涂层抗烧蚀形式主要表现为热化学烧蚀和机械剥蚀。为了提高C/C复合材料的抗氧化烧蚀性能, 采用浆料浸涂与原位反应复合工艺在材料表面制备了ZrB 2 -SiC超高温陶瓷涂层, 利用氧-丙烷火焰测试了涂层的抗烧蚀性能。结果表明: 采用复合工艺所制备的ZrB 2 -SiC超高温陶瓷涂层与基材具有较高的结合强度; 在氧-丙烷火焰冲刷条件下, 涂层具有良好的抗烧蚀性能, 涂层经1500℃下烧蚀600 s, ZrB 2 -SiC涂层无明显烧蚀, C/C复合材料保持完好。微观结构观察表明: 烧蚀测试后, 涂层中存在ZrO 2 和大量超高温陶瓷相, 涂层抗烧蚀形式主要表现为热化学烧蚀和机械剥蚀。

渗硅工艺制备ZrB 2 -SiC涂层的微观结构与抗氧化性能

Novel zirconium diboride-silicon carbide (ZrB2-SiC) coatings were prepared by vapor silicon infiltration (VSI) and liquid silicon infiltration (LSI), respectively. The static oxidation resistance properties of these coatings were evaluated and their microstructure evolution during oxidation was studied. It showed that the VSI coating had better oxidation resistance than LSI. A compact oxide scale was formed on the VSI coating, which strongly suppressed fur- ther oxidation damage during the testing. The poor oxidation resistance of the LSI coating could be mainly attributed to micro-cracks and residual silicon.为了提高陶瓷基复合材料的抗氧化性能，分别采用气相、液相渗硅工艺制备了ZrB 2 -SiC涂层，利用静态氧化试验测试了ZrB 2 -SiC涂层的抗氧化性能，并分析了涂层的微观结构演化过程。结果表明：气相渗硅工艺制备的涂层抗氧化性能更优良，氧化试验后在涂层表面形成一层致密结构的氧化物层，有效抑制氧化性气体向涂层内部扩散，提高涂层的高温抗氧化防护能力。由于液相渗硅工艺制备的涂层存在残留硅成分和微裂纹，导致涂层高温抗氧化防护能力较差。为了提高陶瓷基复合材料的抗氧化性能，分别采用气相、液相渗硅工艺制备了ZrB 2 -SiC涂层，利用静态氧化试验测试了ZrB 2 -SiC涂层的抗氧化性能，并分析了涂层的微观结构演化过程。结果表明：气相渗硅工艺制备的涂层抗氧化性能更优良，氧化试验后在涂层表面形成一层致密结构的氧化物层，有效抑制氧化性气体向涂层内部扩散，提高涂层的高温抗氧化防护能力。由于液相渗硅工艺制备的涂层存在残留硅成分和微裂纹，导致涂层高温抗氧化防护能力较差。

ZrB2-SiC Coatings Prepared by Vapor and Liquid Silicon Infiltration Methods: Microstructure and Oxidation Resistance Property

Novel zirconium diboride-silicon carbide (ZrB2-SiC) coatings were prepared by vapor silicon infiltration (VSI) and liquid silicon infiltration (LSI), respectively. The static oxidation resistance properties of these coatings were evaluated and their microstructure evolution during oxidation was studied. It showed that the VSI coating had better oxidation resistance than LSI. A compact oxide scale was formed on the VSI coating, which strongly suppressed fur- ther oxidation damage during the testing. The poor oxidation resistance of the LSI coating could be mainly attributed to micro-cracks and residual silicon.为了提高陶瓷基复合材料的抗氧化性能，分别采用气相、液相渗硅工艺制备了ZrB 2 -SiC涂层，利用静态氧化试验测试了ZrB 2 -SiC涂层的抗氧化性能，并分析了涂层的微观结构演化过程。结果表明：气相渗硅工艺制备的涂层抗氧化性能更优良，氧化试验后在涂层表面形成一层致密结构的氧化物层，有效抑制氧化性气体向涂层内部扩散，提高涂层的高温抗氧化防护能力。由于液相渗硅工艺制备的涂层存在残留硅成分和微裂纹，导致涂层高温抗氧化防护能力较差。为了提高陶瓷基复合材料的抗氧化性能，分别采用气相、液相渗硅工艺制备了ZrB 2 -SiC涂层，利用静态氧化试验测试了ZrB 2 -SiC涂层的抗氧化性能，并分析了涂层的微观结构演化过程。结果表明：气相渗硅工艺制备的涂层抗氧化性能更优良，氧化试验后在涂层表面形成一层致密结构的氧化物层，有效抑制氧化性气体向涂层内部扩散，提高涂层的高温抗氧化防护能力。由于液相渗硅工艺制备的涂层存在残留硅成分和微裂纹，导致涂层高温抗氧化防护能力较差。