D Jianxin et al/ Int. Journal of Refractory Metals E Hard Materials 27(2009)734-739 a300 b -Radial stress )- Axial stress Radial stress ● Ent Center layer yer Center layer Nozzle axial direction(mm) Nozzle axial direction(mm) 。- Axial stress O- Axial stress 0- Radial stress Radial stress l00 ●●鲁● ●●●●●4● 100 Center layer Entry la 200 12 Fig 3. The resi esses of the layered nozzle with different layer thickness ratios at the inner-hole surface along the nozzle axial direction, (a)Ni nozzle (p=0.2).(b)N2 ozzie (p=0.5).(c)N3 nozzle (p= 1)and( d)N4 nozzle (p=2 c b d 2mm[, 4. SEM micrographs of the cross-section surface of the N4 layered nozzle material. Hardness and fracture toughness at the surface layer(nozzle entry) of the layered ceramic nozzles with different thickness ratios among constituent layers. Hardness(GPa) Fracture toughness(MPa m2) ±12 98±0.6 21.1±1.1 84±0. vered nozzle 09±1.1 7.3±0.5 N4 layered nozzle 206±1.0 5.8±04 N5 stress-free nozzle 199±1.0 4.9±0.5-200 -100 0 100 200 300 0 3 6 9 12 15 Nozzle axial direction (mm) Radial stress (MPa) Axial stress Radial stress Entry layer Center layer -200 -100 0 100 200 300 0 3 6 9 12 15 Nozzle axial direction (mm) Radial stress (MPa) Axial stress Radial stress Entry layer Center layer -200 -100 0 100 200 300 0 3 6 9 12 15 Nozzle axial direction (mm) Radial stress (MPa) Radial stress Axial stress Entry layer Center layer -200 -100 0 100 200 300 0 3 6 9 12 15 Nozzle axial direction (mm) Radial stress (MPa) Axial stress Radial stress Entry layer Center layer a b c d Fig. 3. The residual stresses of the layered nozzle with different layer thickness ratios at the inner-hole surface along the nozzle axial direction, (a) N1 nozzle (p = 0.2), (b) N2 nozzle (p = 0.5), (c) N3 nozzle (p = 1) and (d) N4 nozzle (p = 2). 2mm 150μm 15μm 15μm Entry layer Center layer Exit layer a b c d Fig. 4. SEM micrographs of the cross-section surface of the N4 layered nozzle material. Table 3 Hardness and fracture toughness at the surface layer (nozzle entry) of the layered ceramic nozzles with different thickness ratios among constituent layers. Code name Thickness ratio p = A1/A2 Hardness (GPa) Fracture toughness (MPa m1/2) N1 layered nozzle 0.2 21.6 ± 1.2 9.8 ± 0.6 N2 layered nozzle 0.5 21.1 ± 1.1 8.4 ± 0.5 N3 layered nozzle 1 20.9 ± 1.1 7.3 ± 0.5 N4 layered nozzle 2 20.6 ± 1.0 5.8 ± 0.4 N5 stress-free nozzle 19.9 ± 1.0 4.9 ± 0.5 D. Jianxin et al. / Int. Journal of Refractory Metals & Hard Materials 27 (2009) 734–739 737