Preparation And Properties Of PA66/Al₂O₃ Fiber Reinforced Porous Aluminum-based Ceramic Core

With the development of aeroengine hollow turbine blades,requiring a higher performance of ceramic core.Alumina-based ceramic core with high temperature,chemical stability and thermal expansion is good,but it is difficult in the acid or alkaline solution in the corrosion off,cracking problem seriously restricted the use of aluminum-based ceramic core.Therefore,it is of great theoretical and practical significance to improve the porosity of alumina-based ceramic core.In this paper,PA66 fiber as a pore-forming agent,Al₂O₃ fiber as a reinforcement phase,to ensure the strength of ceramic core under the premise of increasing the porosity.The effects of PA66 fiber content and the proportion of PA66/Al₂O₃ fiber on the composite properties of ceramic core were studied.The enhancement mechanism of fiber properties to ceramic core was analyzed.Experimental results show:?1?PA66 fibers significantly increased the porosity of the alumina-based ceramic core,but the flexural strength decreased.When the PA66 fiber content is 0.9%,the ceramic core porosity is 41.14%,which is 39.45% higher than that of the fiber without fiber,and the flexural strength is 15.33 MPa,weakened by 39.1%.?2?With the decrease of PA66/Al₂O₃ fiber ratio,the content of Al₂O₃ fiber increased,the porosity of ceramic core increased first and then stabilized,and the bending strength at room temperature increased first and then decreased.When the content of Al₂O₃ fiber is 1.2%,the porosity of ceramic core reaches the maximum value of 45.308%.When the content of Al₂O₃ fiber is 1.05%,the bending strength of ceramic core reaches the maximum value of 20.13 MPa,which was 31.3% higher than that without adding Al₂O₃ fiber..?3?PA66 fiber and Al₂O₃ fibers effectively reduces the shrinkage of ceramic core sintering.When the PA66 fiber content was 1.5%,the linear shrinkage of the ceramic core was 0.324%,which was 63.8% lower than that of the ceramic core without fiber addition.When the addition of Al₂O₃ fiber,the linear shrinkage of the core is further reduced.The linear shrinkage of the core with 0.9% PA66 fiber and 1.05% Al₂O₃ fiber reaches the minimum value of 0.199%,which is 77.8% less than that without fiber.The dimensional accuracy of the ceramic core is greatly improved.?4?PA66 fibers make the pores inside the core more porous,small closed pores connected to each other to form pores or even the formation of micro-pores,Al₂O₃ fiber obstructs the pores into the isolated pores from the body to discharge,so that the core porosity becomes larger.Al₂O₃ fiber consumes energy of crack propagation,such as bridging,fracture failure,debonding slip,dissociation and pull out,crack deflection and so on,and plays an important role in enhancing ceramic core.Alumina based ceramic core was prepared with different fiber composite matrix materials and the preparation technology of PA66/Al₂O₃ fiber reinforced porous ceramic core was optimized.The research results provide a new research idea and theoretical basis for improving the performance of ceramic core,which lays the foundation for the development of fiber reinforced high performance ceramic core preparation technology.