Ti(C,N)固溶体的N/C原子比对Ti(C,N)基金属陶瓷组织及力学性能的影响

Effect of N/C Atomic Ratio of Ti(C,N) Solid Solution on Microstructure and Mechanical Properties of Ti(C,N)-based Cermets

本文以不同N/C原子比的Ti(C,N)固溶体为硬质相,通过真空烧结制备了Ti(C,N)基金属陶瓷。用三点弯曲法、洛氏硬度计、压痕法分别测得试样的抗弯强度、硬度、断裂韧性,并通过光学金相显微镜、XRD、SEM、EDS等手段研究了Ti(C,N)固溶体的N/C原子比对Ti(C,N)基金属陶瓷组织的影响规律。结果表明:在一定范围内随着N/C原子比的增大,Ti(C,N)固溶体在液相中溶解度下降,环形相的析出受到抑制,使得金属陶瓷的硬质相芯部逐渐细化且分散均匀,环形相厚度减薄。但Ti(C,N)固溶体的N/C原子比为6∶4及以上时,硬质相与液相之间的润湿性较差,使得金属陶瓷孔隙度增加,显微组织中开始出现亮白色的晶粒。随N/C原子比的增大,金属陶瓷的抗弯强度和硬度先增大后降低,断裂韧性逐渐降低。当Ti(C,N)固溶体的N/C原子比为5∶5时,金属陶瓷的综合力学性能最佳,其抗弯强度为2 429 MPa,硬度为92.2 HRA,断裂韧性为8.44 MPa·m^(1/2)。

Ti（C,N）-based cermets with different N/C atomic ratios of Ti（C,N） solid solution were prepared by vacuum sintering.The mechanical properties of the cermets, such as the transverse rupture strength（TRS）, the hardness（HRA） and the fracture toughness（K（Ⅰc））, were tested by three-point-bending, rockwell apparatus, plamqvist indentation toughness measurement,respectively. The effects of N/C ratio of Ti（C,N） solid solution on microstructures of Ti（C,N）-based cermets were studied by OM,XRD, SEM and EDS. The results show that with the increase of N/C atomic ratio, the ceramic particles of the cermets become finer gradually and distribute evenly, and the rim phase becomes thinner because the solubility of the Ti（C,N） solid solution in the binder decreases and the precipitation of rim phase is inhibited. When the N/C ratio of Ti（C,N） solid solution is 6：4 or more, the wettability between ceramic particles and liquid phase decreases, resulting in the increase of the porosity and the appearance of the bright white grains. With the increase of the N/C atomic ratio, the TRS and HRA of the Ti（C,N）-based cermets increase firstly and then decrease, while the K（Ⅰc）decreases gradually. When the N/C atomic ratio of Ti（C,N） solid solution is 5：5, the cermets show the best mechanical properties with TRS of 2 429 MPa, hardness of 92.2 HRA and K（Ⅰc） of 8.44 MPa·m^1/2.