D Jianxin et al. Materials Science and Engineering A 444(2007)120-129 p (b)/-.949 4.717 59.146 Fig. 11. Distribution of (a) axial (oz), (b)radial(or), and(c)circumferential (ae)residual thermal stresses of GN-3 laminated nozzle on the nozzle bore surface indicating that brittle fracture took temperature to room temperature, which may partially counter- place. Characteristic SEM pictures taken on the eroded entry act the tensile stresses in the nozzle entry section resulting from bore surface of the gn-2 and gn-3 laminated ceramic nozzle external loadings effect may lead to the increase in resis- are shown in Fig. 18. It is shown that the appearance of the tance to fracture, and thus increase the erosion wear resistance eroded areas of the gn-2 and gn-3 laminated nozzle showed a of the laminated nozzle relative smooth surface by contrast with that of the CN-2 stress- free nozzle Ceramic nozzle failure by erosion wear is generally caused by fracture owing large the tensile stress at the nozzle entry zone -o CN-2 stress-free nozzle [11-15]. Because the nozzle entrance region suffers form severe 日GN2 laminated nozzle SN-3 laminated nozzle abrasive impact, and generates large tensile stress, which may ause the subsurface lateral cracks and facilitates removal of the material chips. Thus, the erosion wear of the nozzle depends on the stress distribution in the entry region. Once the maximum tensile stress exceeds the ultimate strength of the nozzle material. will occur The higher erosion wear resistance of the GN-2 and GN-3 laminated nozzle compared with the CN-2 stress-free nozzle can be analysed in terms of the formation of compressive residual stresses on the entry region. As calculated above, compres Erosion time(min) ive residual stresses were formed in the entry region of the 12. Cumulative mass loss of GN-2. GN-3 laminated nozzle and CN-2 Sic/(W,Ti)C laminated nozzle in cooling process from sintering -free nozzle in dry sand blasting processes.126 D. Jianxin et al. / Materials Science and Engineering A 444 (2007) 120–129 Fig. 11. Distribution of (a) axial (σz), (b) radial (σr), and (c) circumferential (σ) residual thermal stresses of GN-3 laminated nozzle. on the nozzle bore surface indicating that brittle fracture took place. Characteristic SEM pictures taken on the eroded entry bore surface of the GN-2 and GN-3 laminated ceramic nozzle are shown in Fig. 18. It is shown that the appearance of the eroded areas of the GN-2 and GN-3 laminated nozzle showed a relative smooth surface by contrast with that of the CN-2 stress￾free nozzle. Ceramic nozzle failure by erosion wear is generally caused by fracture owing large the tensile stress at the nozzle entry zone [11–15]. Because the nozzle entrance region suffers form severe abrasive impact, and generates large tensile stress, which may cause the subsurface lateral cracks and facilitates removal of the material chips. Thus, the erosion wear of the nozzle depends on the stress distribution in the entry region. Once the maximum tensile stress exceeds the ultimate strength of the nozzle material, fracture will occur. The higher erosion wear resistance of the GN-2 and GN-3 laminated nozzle compared with the CN-2 stress-free nozzle can be analysed in terms of the formation of compressive residual stresses on the entry region. As calculated above, compres￾sive residual stresses were formed in the entry region of the SiC/(W,Ti)C laminated nozzle in cooling process from sintering temperature to room temperature, which may partially counter￾act the tensile stresses in the nozzle entry section resulting from external loadings. This effect may lead to the increase in resis￾tance to fracture, and thus increase the erosion wear resistance of the laminated nozzle. Fig. 12. Cumulative mass loss of GN-2, GN-3 laminated nozzle, and CN-2 stress-free nozzle in dry sand blasting processes.