G Model MSA-25534: No a orages ARTICLE IN PRESS D Jianxin et aL Materials Science and Engineering A xxx(2009)xxx-XXx (b) AWT AWT nterface Interface AWT AWT 310 8. Indention cracks on the cross-section of AWT+ AT multilayered ceramic materials, (a)crack in AWT external layer, (b)schematic of the test sample, (c) crack in AT rnal layer. (d)enlarged SEM micrograph corresponding to(a), and(e)enlarged SEM micrograph corresponding to(c) Table 4 Fracture toughness and hardness at the layer of the AWT+ AT multilayered ceramic materials with different thickness ratios among constituent layers. Thickness ratio p Layer number N Hardness(GPa) Fracture toughness (MPa m4) LT-2 208±10 73±0.5 21.0±1 8.4±0.5 21.7±1 100±06 21.8±1.1 10.1±0.6 AWT 199士09 4.9±04 19.9 GPa for AWT stress-free material to 21.9 GPa for LT-4 layered these tools in dry cutting of nodular cast iron is illustrated in Fig. 10. material, representing a maximum increase of 2.0 GPa It is indicated that the layered tools showed more flank wear resis- tance compared with that of AWT stress-free tool under the same 3.4. Cutting performance of the AWT+ AT multilayered cera test conditions. The LT-4 layered tool with a thickness ratio of 8 exhibited the lowest flank wear: while the awr stress-free tool showed the highest flank wear. Tools of16×16×5(mm) in dimension were pre from the Fig 11 shows the SEM micrographs at the wear track of the Awt t-pressed disk by cutting and grinding using a d wheel. stress-free tool and the lt-4 layered tool after 25 min of cutting. Fig 9 shows the photos of LT-2, LT-4, and LT-5 lay Significant surface damage can be observed at the rake face and AWT stress-free tool used in the cutting tests. The wear of cutting edge of the AWT stress-free tool(Fig. 11a). It reveals that (b) Fig 9. Photo of the ceramic tools, (a)AwT stress-free tool, (b)LT-4 layered tool, (c)LT-2 layered tool, and (d)LT-5 layered tooL Please cite this article in press as: D Jianxin, et al, Mater. Sci. Eng. A(2009). doi: 10. 1016/j. msea. 2009.09.020Please cite this article in press as: D. Jianxin, et al., Mater. Sci. Eng. A (2009), doi:10.1016/j.msea.2009.09.020 ARTICLE IN PRESS GModel MSA-25534; No. of Pages 9 6 D. Jianxin et al. / Materials Science and Engineering A xxx (2009) xxx–xxx Fig. 8. Indention cracks on the cross-section of AWT + AT multilayered ceramic materials, (a) crack in AWT external layer, (b) schematic of the test sample, (c) crack in AT internal layer, (d) enlarged SEM micrograph corresponding to (a), and (e) enlarged SEM micrograph corresponding to (c). Table 4 Fracture toughness and hardness at the outer layer of the AWT + AT multilayered ceramic materials with different thickness ratios among constituent layers. Samples Thickness ratio p Layer number N Hardness (GPa) Fracture toughness (MPa m1/2) LT-1 0.5 3 20.5 ± 0.9 6.3 ± 0.5 LT-2 1 3 20.8 ± 1.0 7.3 ± 0.5 LT-3 2 3 21.0 ± 1.0 8.4 ± 0.5 LT-4 8 3 21.9 ± 1.0 10.4 ± 0.6 LT-5 1 5 21.7 ± 1.1 10.0 ± 0.6 LT-6 1 7 21.8 ± 1.1 10.1 ± 0.6 AWT 1 19.9 ± 0.9 4.9 ± 0.4 19.9 GPa for AWT stress-free material to 21.9 GPa for LT-4 layered material, representing a maximum increase of 2.0 GPa. 3.4. Cutting performance of the AWT + AT multilayered ceramic cutting tools Tools of 16 × 16 × 5 (mm) in dimension were prepared from the hot-pressed disk by cutting and grinding using a diamond wheel. Fig. 9 shows the photos of LT-2, LT-4, and LT-5 layered tools, and AWT stress-free tool used in the cutting tests. The flank wear of these tools in dry cutting of nodular cast iron is illustrated in Fig. 10. It is indicated that the layered tools showed more flank wear resis￾tance compared with that of AWT stress-free tool under the same test conditions. The LT-4 layered tool with a thickness ratio of 8 exhibited the lowest flank wear; while the AWT stress-free tool showed the highest flank wear. Fig. 11 shows the SEM micrographs at the wear track of the AWT stress-free tool and the LT-4 layered tool after 25 min of cutting. Significant surface damage can be observed at the rake face and cutting edge of the AWT stress-free tool (Fig. 11a). It reveals that Fig. 9. Photo of the ceramic tools, (a) AWT stress-free tool, (b) LT-4 layered tool, (c) LT-2 layered tool, and (d) LT-5 layered tool