Papers by Author: Yu Huan Fei

Abstract: In this work, two kinds of Al₂O₃-TiC-TiN ceramic cutting tools (AC2U and AC2UN2) were developed by hot-pressing sintering techniques. The mechanical properties were measured and the cutting performance was investigated. The workpiece used in the cutting experiment was quenched carbon tool steel T10A, and the tool material for comparison was LT55. The wear resistance and the main wear patterns of the ceramic tools were analyzed at the high speed of 300m/min. The results indicated that the novel Al₂O₃-TiC-TiN ceramic cutting tools showed better cutting performance than LT55, and AC2UN2 was better suitable for machining quenched T10A. When the cutting condition was v=300m/min, f=0.1mm/r and a_p=0.1mm, the adhesion wear and abrasive wear of the novel ceramic tools were slighter than those of LT55, the diffusion wear resistance of AC2U was better and the oxidation resistance of AC2UN2 was better.

Abstract: This paper analyzes the reasons of the defects generation of the ceramic cutting tool materials. The defects in the ceramic cutting tool materials are caused by chemical compatibility and physical mismatch during the designing process, and caused by grain abnormal growth and sintering parameters during the preparation stage. The database of low defect ceramic cutting tool is established and the data structure of the database is described. The users can use the database to design the tool material system through the mode that can reduce the defects.

Abstract: TiB₂-Ti (C_0.5N_0.5)-WC composite tool materials were fabricated by the hot-pressing technique. The effects of sintering process on microstructure and mechanical properties of TiB₂ -Ti (C_0.5N_0.5) -WC composite tool materials were studied. The flexural strength was measured by three point bending test, and Vickers hardness and the fracture toughness were measured on polished surfaces by Vickers indentation. The microstructure of TiB₂-Ti (C_0.5N_0.5)-WC composite ceramic was analyzed by XRD and SEM observations. The results show that the mechanical properties can be improved in a proper heating mode. When the direct heating-up mode was conducted, the flexural strength, fracture toughness and hardness reached 854MPa, 7.2MPa·m^1/2 and 19.7GPa, respectively.

Abstract: Al₂O₃-TiN-TiC ceramic materials with different MgO content were fabricated by hot-pressing technique. The MgO volume percent was varied from 0vol% to 5vol%. The mechanical properties such as flexural strength, Vickers hardness and fracture toughness were tested. The phase composition of the sintered body was analyzed by XRD while the microstures of the sintering body were observed by OM (Optical Microscope) and SEM. The effects of MgO content on the mechanical properties and microstructures of Al₂O₃-TiN-TiC were investigated. The results shows that the addition of MgO can change the phase composition of the sintered ceramic materials which displayed with diverse solid solutions and intermetallic compounds. Meanwhile the new sintering products changed the the microstructure morphology which made the crack path complex and affected the mechanical properties.

Abstract: Al2O3-TiN-TiC ceramic materials with different MgO content were fabricated by hot-pressing technique. The MgO volume percent was varied from 0vol% to 5vol%. Three point bending test was applied to get the flexural strength and the Vickers indentation was applied to get the Vickers hardness and the fracture toughness. The phase composition of the ceramics was analyzed by XRD. The effects of the content of MgO on the mechanical properties and the phase composition of Al2O3-TiN-TiC were investigated. The results shows that the addition of MgO can change the phase composition of the sintered ceramic materials which displayed with diverse solid solutions and intermetallic compounds. The convertion of the mechanical properties can also be explained by the XRD results.

Abstract: Al2O3-TiN nanocomposite ceramic tool materials were fabricated by hot-pressing technique and the mechanical properties were measured. Mechanical properties such as room temperature flexural strength, Vickers hardness and fracture toughness were measured through three-point bending test and Vickers indentation. The effects of the content of nano-scale TiN, sintering temperature and holding time on the mechanical properties were investigated. The results shows that the addition of nano-scale TiN can improve the mechanical properties of alumina ceramics. Both the flexural strength and the fracture toughness first increased then decreased with an increment in the content of nano-scale TiN. Both the Vickers hardness and the fracture toughness increased with an increment in the sintering temperature. The flexural strength increased with an increment in the holding time, while the fracture toughness decreased with an increment in the holding time. The composites with only nano-scale TiN have the highest Vickers hardness for the holding time of 30min, while the hardness of the composites with nano-scale TiN and micro-scale TiN decreased with an increment in the holding time.