氮化硅基陶瓷刀具材料力学性能和显微结构的研究

Study on Mechanical Property and Microstructure of Si_3N_4 Composite Cutting Tool

研究了混料介质、超声分散、烧结助剂以及纳米第二相颗粒对自增韧氮化硅陶瓷刀具材料的显微结构和力学性能的影响。结果发现：加入5％ Y2O3＋5％ La2O3＋5％CeO2烧结助剂的Si3N4粉体，以水作为混料介质并对混合浆料进行超声分散处理后，在温度为1700，1800℃下、保温40min、压力30MPa条件下热压烧结，材料的综合力学性能较好，抗弯强度可达1002．1Mpa，断裂韧性达8．2MPa·m^1/2，硬度13．56GPa。SEM试验表明材料的显微组织结构均匀，β-Si3N4呈现长棒状交错排列；添加纳米TiC7N3第二相颗粒的氮化硅基陶瓷刀具材料后，β-Si3N4的长径比明显减小，晶界中嵌入了第二相粒子，材料的抗弯强度有所降低，但硬度和韧性则有所升高。

The effects of the mixing medium, ultrasonic dispersing, the content of different sintering additives and nano-Ti （C7N3） on the mechanical properties and microstructure are investigated. The results show that the optimum composition is 5% Y2O3 ＋ 5%La2O3 ＋ 5% CeO2 ＋ 85 %Si3N4 through ultrasonic dispersing at the aqueous medium, and composites exhibit the excellent mechanical properties under the condition of sintering temperature 1700 - 1800℃, soaking for 40min and pressure 30MPa. The flexural strength, fracture toughness and hardness are respectively up to 1002.1MPa, 8.2 MPa·m^1/2 and 13.56GPa. The SEM experiments indicate that the mierostrueture of material is homogenous and the elongated grain of β-Si3N4 is interlaced. In the Si3N4 ceramic composite with the inclusion of nano-TiC7N3, the aspect ratio of grain is decreased remarkably and the second-phase particles is embedded among the interface. As a result, the flexural strength is reduced while the fracture toughness and hardness are improved.