Int. Journal of Refractory Metals Hard Materials 27(2009)734-739 Contents lists available at Science Direct Int. Journal of Refractory Metals Hard Materials ELSEVIER journalhomepagewww.elsevier.com/locate/ijrmhm Design, fabrication and performance of Al2O3 /(Wo.7T10)C+ Al2O3/ TIC multilayered ceramic nozzles Deng Jianxin D,, Yun Dongling, Tan Yuanqiang ool of Mechanical Engineering, Xiangtan University, Xiangtan 411105, Hunan Province, PR China b School of Mechanical Engineering. Shandong University Jinan 250061, Shandong Province, PR China ARTICLE INF O A BSTRACT Article histo Al2O3/Wo.7Tio3)C+Al2O3 Tic multilayered ceramic nozzles(Nl, N2, N3 and N4 )with different thickness Received 2 August 2008 ratios among constituent layers were produced by hot-pressing. The value of the residual stress inside the Accepted 11 December 2008 layered nozzle during fabricating process was calculated by means of the finite element method. The mechanical properties at the surface layer of these layered materials were measured, the microstructure was examined. The wear behaviors of the multilayered nozzles were investigated and compared with an unstressed reference nozzle(N5). Results showed that the multilayered nozzles had superior erosion Nozzles wear resistance to that of the stress free one. The erosion wear resistance of the layered nozzles was Ceramic materials influenced by the thickness ratio among constituent layers. The N4 nozzle with thickness ratio of two Layered materials between adjacent layers exhibited higher erosion wear resistance over the nl N2 and N3 nozzles. Al203 e 2008 Elsevier Ltd. All rights reserved. 1 Introduction axial direction of the nozzle decreases from e and increases from center to exit. the highest tensile Laminated hybrid structures constituted by alternate layers are located on the entry section of the nozzle [13, 1 with different compositions can be properly designed to induce a authors previous studies [15-18. the idea of laminated struc urface compressive residual stress [1-4 The basic idea is to cou- tures was firstly introduced to the design of ceramic nozzles so ple material layers with different thermal expansion coefficients as to form compressive residual stresses at the nozzle (CtE)so that residual stresses arise during cooling from the sinter- exit)region in fabricating process, which may partially ing temperature Residual stresses arise from a mismatch between act the tensile stresses resulting from external loadings the Cte, sintering rates and elastic constants of the constituent showed that laminated structures in Sic/(W, Ti)C nozzle can in- phases and neighbouring layers, and the residual stress field de- duce an excess residual stress in the nozzle during fabricating pends on the geometry of the layered structure and on the thick- process, and this residual stress at the nozzle entry zone is com- ess ratio among layers [5-8. The design of ceramic laminates pressive whatever the sintering temperature [16]. This kind has been proved to be a viable strategy to obtain significant in- compressive residual stress can result in an improved erosion reases of the fracture resistance of ceramic materials. The effec wear resistance of the laminated nozzle compared with the tiveness of laminated structures in oving the tribological homologous stress-free one. properties has been also reported 9, 10. Toschi et al [11]reported In the present study, Al 2O3/(Wo.7Tio3) C+ Al2O3 TiC multilay- that laminated hybrid structures can improve the sliding wear ered ceramic nozzles with different thickness ratios among constit- sistance of alumina de portu et al. [12 showed that laminated uent layers were produced by hot-pressing in order to induce structures with compressive residual stresses within the surface compressive residual stress both at the entry and at the exit re egions were a suitable way to obtain composite materials with gions. The residual stress inside the layered nozzles during the sin- superior tribological properties tering process was calculated by means of the finite element The nozzle entrance section suffers severe abrasive impact, method(FEM). The mechanical properties at the surface layers of and generates the largest tensile stress. The stresses along the the layered materials were measured, the microstructure was examined. The wear behaviors of the multilayered nozzles were investigated and compared with an unstressed reference nozzle Particular attention was paid to the effect of thickness ratio among Address: School of Mechanical Engineering. shar vear behaviors of Al2O3/(Wo.7Tio3)C+ andong province, PR China Tel. +86 0531 8839 ndong constituent layers on the w Al2O3/TiC multilayered nozzles 0263-4368/s- see front matter o 2008 Elsevier Ltd. All rights reserved. do:101016 ijrmhm2008.12004Design, fabrication and performance of Al2O3/(W0.7Ti0.3)C + Al2O3/TiC multilayered ceramic nozzles Deng Jianxin a,b,*, Yun Dongling b , Tan Yuanqiang a a School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, Hunan Province, PR China b School of Mechanical Engineering, Shandong University, Jinan 250061, Shandong Province, PR China article info Article history: Received 2 August 2008 Accepted 11 December 2008 Keywords: Nozzles Residual stress Ceramic materials Layered materials Al2O3 abstract Al2O3/(W0.7Ti0.3)C + Al2O3/TiC multilayered ceramic nozzles (N1, N2, N3 and N4) with different thickness ratios among constituent layers were produced by hot-pressing. The value of the residual stress inside the layered nozzle during fabricating process was calculated by means of the finite element method. The mechanical properties at the surface layer of these layered materials were measured, the microstructure was examined. The wear behaviors of the multilayered nozzles were investigated and compared with an unstressed reference nozzle (N5). Results showed that the multilayered nozzles had superior erosion wear resistance to that of the stress-free one. The erosion wear resistance of the layered nozzles was influenced by the thickness ratio among constituent layers. The N4 nozzle with thickness ratio of two between adjacent layers exhibited higher erosion wear resistance over the N1, N2 and N3 nozzles. 2008 Elsevier Ltd. All rights reserved. 1. Introduction Laminated hybrid structures constituted by alternate layers with different compositions can be properly designed to induce a surface compressive residual stress [1–4]. The basic idea is to cou￾ple material layers with different thermal expansion coefficients (CTE) so that residual stresses arise during cooling from the sinter￾ing temperature. Residual stresses arise from a mismatch between the CTE, sintering rates and elastic constants of the constituent phases and neighbouring layers, and the residual stress field de￾pends on the geometry of the layered structure and on the thick￾ness ratio among layers [5–8]. The design of ceramic laminates has been proved to be a viable strategy to obtain significant in￾creases of the fracture resistance of ceramic materials. The effec￾tiveness of laminated structures in improving the tribological properties has been also reported [9,10]. Toschi et al. [11] reported that laminated hybrid structures can improve the sliding wear resistance of alumina. de Portu et al. [12] showed that laminated structures with compressive residual stresses within the surface regions were a suitable way to obtain composite materials with superior tribological properties. The nozzle entrance section suffers severe abrasive impact, and generates the largest tensile stress. The stresses along the axial direction of the nozzle decreases from entry to center, and increases from center to exit. The highest tensile stresses are located on the entry section of the nozzle [13,14]. In the author’s previous studies [15–18], the idea of laminated struc￾tures was firstly introduced to the design of ceramic nozzles so as to form compressive residual stresses at the nozzle entry (or exit) region in fabricating process, which may partially counter￾act the tensile stresses resulting from external loadings. Results showed that laminated structures in SiC/(W, Ti)C nozzle can in￾duce an excess residual stress in the nozzle during fabricating process, and this residual stress at the nozzle entry zone is com￾pressive whatever the sintering temperature [16]. This kind of compressive residual stress can result in an improved erosion wear resistance of the laminated nozzle compared with the homologous stress-free one. In the present study, Al2O3/(W0.7Ti0.3)C + Al2O3/TiC multilay￾ered ceramic nozzles with different thickness ratios among constit￾uent layers were produced by hot-pressing in order to induce a compressive residual stress both at the entry and at the exit re￾gions. The residual stress inside the layered nozzles during the sin￾tering process was calculated by means of the finite element method (FEM). The mechanical properties at the surface layers of the layered materials were measured, the microstructure was examined. The wear behaviors of the multilayered nozzles were investigated and compared with an unstressed reference nozzle. Particular attention was paid to the effect of thickness ratio among constituent layers on the wear behaviors of Al2O3/(W0.7Ti0.3)C + Al2O3/TiC multilayered nozzles. 0263-4368/$ - see front matter 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijrmhm.2008.12.004 * Corresponding author. Address: School of Mechanical Engineering, Shandong University, Jinan 250061, Shandong Province, PR China. Tel.: +86 0531 88392047. E-mail address: jxdeng@sdu.edu.cn (D. Jianxin). Int. Journal of Refractory Metals & Hard Materials 27 (2009) 734–739 Contents lists available at ScienceDirect Int. Journal of Refractory Metals & Hard Materials journal homepage: www.elsevier.com/locate/IJRMHM