标题：Fabrication and mechanical properties of Si3N4/(W, Ti)C/Co graded nano-composite ceramic tool materials
作者：Tian, Xianhua;Zhao, Jun;Wang, Yintao;Gong, Feng;Qin, Wenzhen;Pan, Helin
作者机构：[Tian, X] Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE, School of Mechanical Engineering, Shandong University, Jinan, 250 更多
通讯作者地址：[Zhao, J]Shandong Univ, Sch Mech Engn, Key Lab High Efficiency & Clean Mech Mfg MOE, Jinan 250061, Peoples R China.
关键词：Graded ceramic tool material;Si3N4/(W;Ti)C/Co;Mechanical properties;Microstructure;Toughening and strengthening mechanisms
摘要：Si3N4/(W, Ti)C/Co nano-composite ceramic tool materials with multilayered structure were fabricated by hot pressing technology. The composites without Co were used as the surface layers and the composites containing Co were used as the inner layers. The flexural strength, fracture toughness, and hardness of the composites were tested, and the fracture surfaces and indention cracks were observed. The experimental results showed that the flexural strength and fracture toughness were largely increased by the graded structure and the high hardness was still maintained. The five-layer graded nano-composites, with a thickness ratio of 0.2, which were sintered under a pressure of 30 MPa at 1700 degrees C in vacuum condition for 45 min, had the optimum comprehensive mechanical properties with a flexural strength of 992 MPa, a hardness of 17.83 GPa, and a fracture toughness of 10.5 MPa . m(1/2). The formation of elongated beta-Si3N4 grains and the residual compressive stress in the surface layer induced by the graded structure contributed to the improved properties. A synergistic effect of intergranular and transgranular fracture, crack bridging, and deflection contributed to the strengthening and toughening mechanisms. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.