通过热压烧结制备了以2%(质量分数)MgO–8%Lu_2O_3和2%MgO–8%Gd_2O_3为烧结助剂的2种Si_3N_4刀具(分别记作SN–L和SN–G)。以HT250为工件材料,对其切削性能进行了研究。结果表明:SN–G切削过程更稳定,刀具寿命更长,其有效切削长度约为2 600 m,是SN–L的2倍左右。两者后刀面磨损形貌没有明显差别,磨粒磨损和黏结磨损是主要的磨损机理。SN–G基体的晶粒较细小,增强晶粒的长径比较高,其抗弯强度和断裂韧性均比SN–L高10%左右,具有更高的晶界结合强度,在切削过程中不易发生晶粒脱落,因而刀具耐磨性更好,寿命更长。 Two kinds of Si_3N_4 cutting tools (SN-L and SN-G respectively) were prepared by hot-pressing sintering with 2% (mass fraction) MgO-8% Lu_2O_3 and 2% MgO-8% Gd_2O_3 as sintering aids. Taking HT250 as workpiece material, the cutting performance was studied. The results show that the cutting process of SN-G is more stable and the tool life is longer. The effective cutting length is about 2 600 m, which is about 2 times that of SN-L. There is no obvious difference between flank wear morphology and abrasive wear and bond wear, which are the main wear mechanisms. The grains of SN-G matrix are finer and the longer diameter ratio of the strengthened grains is higher. The flexural strength and fracture toughness of the SN-G matrix are both about 10% higher than that of SN-L, which results in higher grain boundary bond strength and less difficulty in cutting process. Occur grain off, so tool wear better, longer life expectancy.