Effects of Sintering Temperature on Microstructure and Mechanical Properties of Silicon Nitride Layered Ceramics
The alternate layering technique was used to successfully prepare a layered powder billet with α-Si3N4 as the matrix,Y2O3-MgO-WC and GdF3-MgO as the additive phase of A layer and B layer,respectively.Using vacuum hot pressing sintering technology,the sintering temperature of 1550℃,1600℃,1650℃,1700℃,1750℃,the pressure was 30 MPa,the holding time was 60 min,the silicon nitride layered ceramic material was prepared.The effects of sintering temperature on the microstructure and mechanical properties of silicon nitride layered ceramics were studied.The results show that the fracture toughness of layered ceramic materials increases first and then decreases with the increase of sintering temperature.When the sintering temperature is 1650℃,the fracture toughness is highest,the midplane fracture toughness is 7.844 MPa·m1/2,and the layer fracture toughness is 7.294 MPa·m1/2.At the same time,with the increase of sintering temperature,the flexural strength and hardness of laminated ceramic materials first decrease and then increase.When the sintering temperature is 1550℃,the flexural strength is 841.797 MPa,the surface Vickers hardness is 16.227 GPa.In addition,the fracture mode of layered ceramic materials is a hybrid mode of transgranular fracture and intergranular fracture.
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