D Jianxin et al. International Journal of Machine Tools Manufacture 45(2005)1393-1401 Table 3 HRC46 in the form of round bar with an external diameter Experimental conditions of 150 mm. The compositions of the material are listed in 50-18 Table 2. No cutting fluid was used in the machining Feed rate(mm/rev) processes. The experimental conditions are shown in Depth of cut(mm) Table 3 Tool flank wear was measured using a X20 optional microscope system linked via transducers to a digital read out. The average cutting temperature of the tool rake face was measured by means of nature thermocouple technique Mechanical properties of Al]O,/TiB2/SiCw ceramic tool materials with [18]. The worn rake and flank regions on the ceramic tools different volume fraction of TiB2 particles and SiC whiskers were examined using scanning electron microscopy rdness Flexural Fracture HITACH S-570). Electron microprobe analysis was used to analyze the adhesion and the element diffusion 9984 3. Results and discussions ABW 22.0 670 3.1. Mechanical properties and microstructural the measurement of flexural strength. vickers hardness and characterization fracture toughness. A three-point bending mode was used to measure the flexural strength over a 30 mm span at a Results of the fracture toughness, flexural strength, crosshead speed of 0.5 mm/min. Fracture toughness hardness and relative densities of the composite tool measurement was performed using indentation method in materials with different TiB2 and Sicw content are presented a hardness tester(ZWICK3212)using the formula proposed in Table 4. It was shown that the fracture toughness and by Cook and Lawn [17]. On the same apparatus the vickers hardness continuously increased with increasing SiCw hardness was measured on the polished surface with a load content up to 30 vol %. The relative density of the of 98 N. Data for flexural strength, hardness and fracture composites decreased with increasing SiCw content, toughness were gathered on five specimens the trend of the flexural strength being the same as that of the relative density. The decrease of flexural strength with increasing SiCw content is likely due to the decrease in the 2.3. Cutting tests relative density associated with SiCw agglomerates [9, 16 Fig. 1 shows SEM micrograph of the fracture surface Cutting tests were carried out on a CA6140 lathe of ABw20 ceramic tool material. As can be seen that equipped with a commercial tool holder having the the composite exhibited a rough fracture surface, and the following geometry: rake angle Yo=-5, clearance angle fracture mode was mixed transgranular and intergranular. Co=5, inclination angle As=-5, side cutting edge angle Protruding whiskers and holes where whiskers were lodged Kr=75, bro Xro1=0.2X(-20). The geometry of the prior to fracture were observed(Fig. 1(b), and these Al2O3/TiB2/SiCw tool inserts was of ISo SNGN150608 evidences of whisker pullout and bridging with a 0. 2 mm at 20 edge chamfer. The work piece material The SEM micrograph of the polished surfaces perpen- used was Inconel718 nickel-based alloy with a hardness of dicular to the hot pressing direction of AB W20 ceramic tool Fig 1 SEM micrographs of the fracture surface of ABW20 ceramic tool material.the measurement of flexural strength, Vickers hardness and fracture toughness. A three-point bending mode was used to measure the flexural strength over a 30 mm span at a crosshead speed of 0.5 mm/min. Fracture toughness measurement was performed using indentation method in a hardness tester (ZWICK3212) using the formula proposed by Cook and Lawn [17]. On the same apparatus the Vickers hardness was measured on the polished surface with a load of 98 N. Data for flexural strength, hardness and fracture toughness were gathered on five specimens. 2.3. Cutting tests Cutting tests were carried out on a CA6140 lathe equipped with a commercial tool holder having the following geometry: rake angle g0ZK58, clearance angle a0Z58, inclination angle lsZK58, side cutting edge angle KrZ758, br0!r01Z0.2!(K208). The geometry of the Al2O3/TiB2/SiCw tool inserts was of ISO SNGN150608 with a 0.2 mm at 208 edge chamfer. The work piece material used was Inconel718 nickel-based alloy with a hardness of HRC46 in the form of round bar with an external diameter of 150 mm. The compositions of the material are listed in Table 2. No cutting fluid was used in the machining processes. The experimental conditions are shown in Table 3. Tool flank wear was measured using a !20 optional microscope system linked via transducers to a digital read out. The average cutting temperature of the tool rake face was measured by means of nature thermocouple technique [18]. The worn rake and flank regions on the ceramic tools were examined using scanning electron microscopy (HITACH S-570). Electron microprobe analysis was used to analyze the adhesion and the element diffusion. 3. Results and discussions 3.1. Mechanical properties and microstructural characterization Results of the fracture toughness, flexural strength, hardness and relative densities of the composite tool materials with different TiB2 and SiCw content are presented in Table 4. It was shown that the fracture toughness and hardness continuously increased with increasing SiCw content up to 30 vol.%. The relative density of the composites decreased with increasing SiCw content, the trend of the flexural strength being the same as that of the relative density. The decrease of flexural strength with increasing SiCw content is likely due to the decrease in the relative density associated with SiCw agglomerates [9,16]. Fig. 1 shows SEM micrograph of the fracture surface of ABW20 ceramic tool material. As can be seen that the composite exhibited a rough fracture surface, and the fracture mode was mixed transgranular and intergranular. Protruding whiskers and holes where whiskers were lodged prior to fracture were observed (Fig. 1(b)), and these are evidences of whisker pullout and bridging. The SEM micrograph of the polished surfaces perpen￾dicular to the hot pressing direction of ABW20 ceramic tool Table 4 Mechanical properties of Al2O3/TiB2/SiCw ceramic tool materials with different volume fraction of TiB2 particles and SiC whiskers Specimen Relative density (g/cm3 ) Hardness (GPa) Flexural strength (MPa) Fracture toughness (MPa m1/2) ABW05 99.90 21.4 778 5.90 ABW10 99.84 21.6 750 7.60 ABW20 99.42 21.7 726 7.97 ABW30 98.93 22.0 670 8.42 Table 3 Experimental conditions Cutting speed (m/min) 50–180 Feed rate (mm/rev) 0.15 Depth of cut (mm) 0.3 Environment Dry Fig. 1. SEM micrographs of the fracture surface of ABW20 ceramic tool material. D. Jianxin et al. / International Journal of Machine Tools & Manufacture 45 (2005) 1393–1401 1395