D Jianxin et al. Materials Science and Engineering A 444 (2007)120-129 Hardness of different layers of the SiC/(,TiC laminated nozzle(GN-2) Layer (W,TiC content (vol %) Vickers hardness, Hy(GPa) 26.52 3 4 5 24.67 6 where P is the indentation load (N), 2a is the catercorner length (um) due to indentation. Hardness of each layer of SiC/(W,Ti)C laminated nozzle(GN-2)material is presented in Table 2 ig. 7 illustrates -ray diffraction analysis Sic/W,Ti)C laminated ceramic nozzle(GN-2) material after Fig. 6. Photo of the SiC/w,Ti)C laminated ceramic nozzles. sintering at 1900 C for 40 min. It can be seen that both (w,Tic and Sic existed in the sintered specimens. SEM micrograph of each polished layer of Sic/(W,Ti)C laminated ceramic noz- The finite element method(FEM) was used as a means of zle(Gn-2)material are shown in Fig 8. The black areas were numerically evaluating the residual thermal stress and its dis- identified by EDX analysis as SiC, and the white phases with tribution of the laminated ceramic nozzle in the fabricating clear contrast were(W,Ti)C. It can be seen that the Sic particles processes are quite uniformly distributed throughout the microstructure. For observation of the micro-damage and determination of porosity is virtually absent. erosion mechanisms, the worn nozzles were sectioned axially The eroded bore surfaces of the nozzles were examined by scan- ning electron microscopy. 3.2. Residual thermal stress analysis of sic/(W,Ti)C laminated nozzle material 3. Results and discussion The residual thermal stress of the laminated ceramic noz- zle in the fabricating process was calculated by means of the 3.1. Microstructural characterization and properties of finite element method by assuming that the compact is cooled Sic(W, Ti)C laminated nozzle materials from sintering temperature 1900C to room temperature 20oC Thermo-mechanical properties of (W,Ti)C and Sic are as fol- Hardness measurements were performed by placing Vick- lows: rs indentations on every layer of the cross-sectional surface of SiC/W,Ti)C laminated nozzle (GN-2)material. The indentation (W, Ti)C: E=480 GPa, v=0.25, a=85x10 K load was 200N and a minimum of three indentations were tested for each layer. The Vickers hardness( GPa)of each layer is given k=214W/mK) P Hy=1.8544 (2a)2 4000 Table 1 3000 Dry sand blasting test conditions Sand blasting equipment GS-6 type sand blasting machine tool Sic/(W,Ti)C ceramic nozzle laminated only in Nozzle material entry area( GN-2 SiC/W, Ti)C ceramic nozzle laminated both in entry and exit area(GN-3) SiC/(W,Ti)C stress-free nozzle(CN-2) Dimension of nozzle omm(internal diameter)x 30 mm(length) 50-150um SiC powders 0.4 MPa Cumulative mass weigh Accurate electronic balance(minimum 0.1 mg) Fig. 7. X-ray diffraction analysis of the SiC/(W,Ti)c laminated ceramic nozzle material(GN-2)after sintering at 1900C for 40 minD. Jianxin et al. / Materials Science and Engineering A 444 (2007) 120–129 123 Fig. 6. Photo of the SiC/(W,Ti)C laminated ceramic nozzles. The finite element method (FEM) was used as a means of numerically evaluating the residual thermal stress and its dis￾tribution of the laminated ceramic nozzle in the fabricating processes. For observation of the micro-damage and determination of erosion mechanisms, the worn nozzles were sectioned axially. The eroded bore surfaces of the nozzles were examined by scan￾ning electron microscopy. 3. Results and discussion 3.1. Microstructural characterization and properties of SiC/(W,Ti)C laminated nozzle materials Hardness measurements were performed by placing Vick￾ers indentations on every layer of the cross-sectional surface of SiC/(W,Ti)C laminated nozzle (GN-2) material. The indentation load was 200 N and a minimum of three indentations were tested for each layer. The Vickers hardness (GPa) of each layer is given by: Hv = 1.8544 P (2a) 2 (2) Table 1 Dry sand blasting test conditions Sand blasting equipment GS-6 type sand blasting machine tool Nozzle material SiC/(W,Ti)C ceramic nozzle laminated only in entry area (GN-2) SiC/(W,Ti)C ceramic nozzle laminated both in entry and exit area (GN-3) SiC/(W,Ti)C stress-free nozzle (CN-2) Dimension of nozzle Ø 8 mm (internal diameter) × 30 mm (length) Erodent abrasives 50–150m SiC powders Compressed air pressure 0.4 MPa Cumulative mass weigh Accurate electronic balance (minimum 0.1 mg) Table 2 Hardness of different layers of the SiC/(W,Ti)C laminated nozzle (GN-2) materials Layer (W,Ti)C content (vol.%) Vickers hardness, Hv (GPa) 1 55 26.89 2 57 26.52 3 59 25.93 4 61 25.70 5 63 24.67 6 65 24.15 where P is the indentation load (N), 2a is the catercorner length (m) due to indentation. Hardness of each layer of SiC/(W,Ti)C laminated nozzle (GN-2) material is presented in Table 2. Fig. 7 illustrates the X-ray diffraction analysis of the SiC/(W,Ti)C laminated ceramic nozzle (GN-2) material after sintering at 1900 ◦C for 40 min. It can be seen that both (W,Ti)C and SiC existed in the sintered specimens. SEM micrographs of each polished layer of SiC/(W,Ti)C laminated ceramic noz￾zle (GN-2) material are shown in Fig. 8. The black areas were identified by EDX analysis as SiC, and the white phases with clear contrast were (W,Ti)C. It can be seen that the SiC particles are quite uniformly distributed throughout the microstructure, porosity is virtually absent. 3.2. Residual thermal stress analysis of SiC/(W,Ti)C laminated nozzle material The residual thermal stress of the laminated ceramic noz￾zle in the fabricating process was calculated by means of the finite element method by assuming that the compact is cooled from sintering temperature 1900 ◦C to room temperature 20 ◦C. Thermo-mechanical properties of (W,Ti)C and SiC are as fol￾lows: (W, Ti)C : E = 480 GPa, ν = 0.25, α = 8.5 × 10−6 K−1, k = 21.4 W/(m K). Fig. 7. X-ray diffraction analysis of the SiC/(W,Ti)C laminated ceramic nozzle material (GN-2) after sintering at 1900 ◦C for 40 min.