| High temperature structural ceramics have drawn great attention for their excellent combination properties of high strength, high hardness, corrosion resistance, which make ceramics have a wide range of applications for the aerospace, machinery, chemicals and other fields. However, structural ceramics is very brittle and sensitive to surface crack, resulting in poor reliability and damage resistance, which has affected the scope of its application seriously. In view of their low toughness and unsatisfactory thermal shock resistance, we propose a new method for strengthening and toughening design of ceramics that combines shot peening with crack-healing ability in this paper.Through the research of high-temperature structural ceramics surface peening process optimization, we explore the effect of shot peening process parameters on the mechanical properties of materials, and the results can provide a precise guidance on experiment. Besides, for porous TiB2-SiC ceramics and dense ZrB2-SiC ceramics, we established a quantitative relationship between an increase in the mechanical properties and the parameters of toughening method, and study its mechanism of strengthing. These works coule provide a precise guidance on strengthening and toughening design, performance optimization, and life evaluation for high-temperature structural ceramics. The works carried out in this paper are as followers:1. Using finite element software ABAQUS established shot peening process model, and adjusted the different parameters of shot peening process to analyze the residual stress field. The results show that shot peening induced residual stress in the ceramic samples, and this method can effectively improve the strength of the ceramic samples.2. In order to explore the applicability of the crack healing method for porous structural ceramics, we study the toughening of porous TiB2-SiC ceramic. The samples were pre-oxidation at 800℃-1400℃ for 5min-360min. The effect of pre-oxidation temperature and time on the microstructure and mechanical properties of porous TiB2-SiC ceramics were investigated.3. Take ZrB2-SiC ceramics as research objects, we propose a new method for improving the strength and reliability of ceramics that combines shot peening with multiple crack-healing. To evaluate the effect of our method, we examined the specimens’mechanical properties of different process parameters. It was found that shot peening and multiple crack healing process is effective to increase flexural strength.Results showed here enrich and develop the basic mechanisms of strengthening and toughening design for high-temperature structural ceramics, and afford reliable foundation for this kind of composite to be used in thermal protection systems and propulsion systems for National high-tech equipment. |
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