MATERIALS HIENGE& ENGIEERING ELSEVIER Materials Science and Engineering A 444 (2007)120-129 www.elsevier.com/locate/msea Erosion wear behaviours of Sic/(w,Ti)c laminated ceramic nozzles in dry sand blasting processes Deng jianxin. Liu Lili. dir Department of Mechanical Engineering, Shandong University, Jinan 250061, Shandong Province, PR China Received 13 April 2006: accepted 17 August 2006 In sand blasting processes, the nozzle entry region suffers form severe abrasive impact, which may cause large tensile stress and lead to an increased erosion wear at the nozzle entry area. In this paper, SiC/W, Ti)c laminated ceramic nozzles were produced by hot pressing. The purpose to reduce the tensile stress at the entry region of the nozzle. Due to the different thermal expansion coefficients and shrinkage of the Sic and W,Ti)C solid-solution, the entry region of the Sic/(w,Ti)C laminated ceramic nozzles in the fabricating process exhibit a compressive residual stress. The value of this residual stress was calculated by means of the finite element method. The erosion wear behaviour of the laminated ceramic nozzle and of a stress-free nozzle, with the same composition, was assessed by dry sand blasting Results showed that the laminated ceramic nozzles have superior erosion wear resistance to that of the homologous stress-free nozzles. The mechanism responsible was explained as the formation of compressive residual stresses in nozzle entry region in fabricating process of the laminated ceramic nozzles, which may partially counteract the tensile stresses resulting from extermal loadings, and leads to an improvement of erosion wear resistance. It is indicated that laminated structures in ceramic nozzles is an effective way to improve the erosion wear resistance of the stress-free nozzles C 2006 Elsevier B. V. All rights reserved. Keywords: Nozzles: Ceramic materials: Laminated materials: SiC 1. Introduction The nozzle is the most critical part in the sand blasting treatment equipment. There are many factors that influence the Sand blasting treatment is an abrasive machining process and nozzle wear such as: the mass flow rate and impact angle [5-7] is widely used for surface strengthening[l], surface modification the erodent abrasive properties [8-10, the nozzle material and 21, surface clearing and rust removal [3, 4], etc. It is suitable for its geometry [11-16], and the temperatures [17, 18]. Ce the treatment of hard and brittle materials, ductile metals, alloys, being highly wear resistance, have great potential as and nonmetallic materials, and can provide perfect surface treat- blasting nozzle materials ment to all kinds workpieces from hull, steel structure, container Several studies [11-15] have shown that the entry area of to watchcase, button and inject needle In the sand blasting pro- a ceramic nozzle exhibited a brittle fracture induced removal cess, a very high velocity jet of fine abrasive particles and carrier process, while the centre area showed plowing type of material gas coming out from a nozzle impinges on the target surface and removal mode. As the erosive particles hit the nozzle at high erodes it. The fine particles are accelerated by the gas stream, angles(nearly 90%) at the nozzle entry section in sand blasting commonly compressed air at a few times atmospheric pressure. (see Fig. 1), the nozzle entry region suffers form severe abrasive The particles are directed towards the surfaces to be treated. impact, which may cause large tensile stresses. The stress alon As the particles impact the surface, they cause a small fracture, the axial direction of the nozzle decreases from entry to centre, and the gas stream carries both the abrasive particles and the and increases from centre to exit. The highest tensile stresses fractured particles away are located at the entry region of the nozzle. While the wear of the nozzle centre area changes from impact to slidin the tensile stresses caused by the abrasive impact in this area are much smaller than those at the entry section. Thus, the erosion Corresponding author. Tel: +86 531 88392047 wear of the nozzle entry region is always serious in contrast with E-mail address sdu.edu. cn(D. Jianxin) that of the centre area [11-15] )6 Elsevier B v. All rights reservedMaterials Science and Engineering A 444 (2007) 120–129 Erosion wear behaviours of SiC/(W,Ti)C laminated ceramic nozzles in dry sand blasting processes Deng Jianxin ∗, Liu Lili, Ding Mingwei Department of Mechanical Engineering, Shandong University, Jinan 250061, Shandong Province, PR China Received 13 April 2006; accepted 17 August 2006 Abstract In sand blasting processes, the nozzle entry region suffers form severe abrasive impact, which may cause large tensile stress and lead to an increased erosion wear at the nozzle entry area. In this paper, SiC/(W,Ti)C laminated ceramic nozzles were produced by hot pressing. The purpose is to reduce the tensile stress at the entry region of the nozzle. Due to the different thermal expansion coefficients and shrinkage of the SiC and (W,Ti)C solid-solution, the entry region of the SiC/(W,Ti)C laminated ceramic nozzles in the fabricating process exhibit a compressive residual stress. The value of this residual stress was calculated by means of the finite element method. The erosion wear behaviour of the laminated ceramic nozzle and of a stress-free nozzle, with the same composition, was assessed by dry sand blasting. Results showed that the laminated ceramic nozzles have superior erosion wear resistance to that of the homologous stress-free nozzles. The mechanism responsible was explained as the formation of compressive residual stresses in nozzle entry region in fabricating process of the laminated ceramic nozzles, which may partially counteract the tensile stresses resulting from external loadings, and leads to an improvement of erosion wear resistance. It is indicated that laminated structures in ceramic nozzles is an effective way to improve the erosion wear resistance of the stress-free nozzles. © 2006 Elsevier B.V. All rights reserved. Keywords: Nozzles; Ceramic materials; Laminated materials; SiC 1. Introduction Sand blasting treatment is an abrasive machining process and is widely used for surface strengthening [1], surface modification [2], surface clearing and rust removal [3,4], etc. It is suitable for the treatment of hard and brittle materials, ductile metals, alloys, and nonmetallic materials, and can provide perfect surface treat￾ment to all kinds workpieces from hull, steel structure, container to watchcase, button and inject needle. In the sand blasting pro￾cess, a very high velocity jet of fine abrasive particles and carrier gas coming out from a nozzle impinges on the target surface and erodes it. The fine particles are accelerated by the gas stream, commonly compressed air at a few times atmospheric pressure. The particles are directed towards the surfaces to be treated. As the particles impact the surface, they cause a small fracture, and the gas stream carries both the abrasive particles and the fractured particles away. ∗ Corresponding author. Tel.: +86 531 88392047. E-mail address: jxdeng@sdu.edu.cn (D. Jianxin). The nozzle is the most critical part in the sand blasting treatment equipment. There are many factors that influence the nozzle wear such as: the mass flow rate and impact angle [5–7], the erodent abrasive properties [8–10], the nozzle material and its geometry [11–16], and the temperatures [17,18]. Ceramics, being highly wear resistance, have great potential as the sand blasting nozzle materials. Several studies [11–15] have shown that the entry area of a ceramic nozzle exhibited a brittle fracture induced removal process, while the centre area showed plowing type of material removal mode. As the erosive particles hit the nozzle at high angles (nearly 90◦) at the nozzle entry section in sand blasting (see Fig. 1), the nozzle entry region suffers form severe abrasive impact, which may cause large tensile stresses. The stress along the axial direction of the nozzle decreases from entry to centre, and increases from centre to exit. The highest tensile stresses are located at the entry region of the nozzle. While the wear of the nozzle centre area changes from impact to sliding erosion, the tensile stresses caused by the abrasive impact in this area are much smaller than those at the entry section. Thus, the erosion wear of the nozzle entry region is always serious in contrast with that of the centre area [11–15]. 0921-5093/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2006.08.090