Handbook of Advanced Ceramics Machining Episode 7 potx

0 0.5 1 1.5 2 2.5 #325 #600 #1200 #2000 #4000 #8000 #30000 R y , µm Mesh size R y 0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 #325 #600 #1200 #2000 #4000 #8000 #30000 R a , µm Mesh sizeMesh size R a (a) (b) FIGURE 6.20 Relation between mesh size and surface roughness. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 166 6.10.2006 2:18am 166 Handbook of Advanced Ceramics Machining A dramatic improvement in the roughness of ground surface was con- firmed between #600 and #2000 wheels. This is attributed to changes in the material removal mechanism between the two grains. By final-finish machining using #30000 abrasive, a satisfactory surface roughness of 0.008 mm R a was obtained. Significant improvement in surface roughness and form accuracy was successfully achieved by fine-grit wheels using the ELID technique. Figure 6.21 shows the behavior of the electrolytic current for processing using a #4000 grinding wheel. The current is low at the initial electrolysis stage and increases after the wheel comes in contact with the workpiece. There is no subsequent variation with processing time, and the current remains con- stant at approximately 0.25 A, indicating that the ELID conditions are appropriate and that stable processing occurs from beginning till the end. This trend in current values was confirmed for all of the other wheels, in addition to the #4000 wheel. A finished example is shown in Figure 6.22. 6.5.2 Observation of the ELID Ground Surface Figure 6.23 shows the results of SEM observations of the ground surfaces obtained with #325 to #30000 grinding wheels. The surfaces ground with the #325 and #600 wheels demonstrate a rough processed state with the material removed by the breakdown of the grain boundary. On the surface, ground with the #1200 wheel, small areas in which the material was removed by 0 0.05 0.10 0.15 0.20 0.25 0.30 0 5 10 15 20 Electrolytic current, A Time, min Initial electrolysis dressing FIGURE 6.21 Behavior of the electrolytic current for processing using a #4000 grinding wheel. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 167 6.10.2006 2:18am Electrolytic In-Process Dressing Grinding of Ceramic Materials 167 means other than the breakdown of the grain boundary were confirmed. However, in the same way as the surface ground with the #325 wheel, most of the areas were removed in the brittle failure mode, in which the break- down of the grain boundary is the principle mechanism. Conversely, the surfaces ground with the #2000, #8000, and #30000 wheels were processed to a smooth surface, with almost no breakdown in the grain boundary. SEM observations of machined surfaces confirmed that between rough machining with #1200 abrasive and intermediate finishing with #2000 abrasive, there exists a brittle–ductile transition point for aluminum nitride. In order to create a high-quality machined surface, the use of fine abrasive particles of at least #2000 is essential. Figure 6.24 summarizes the relation- ship between the wheel mesh size and the removal mechanism when ELID grinding is used. These results demonstrate that ELID with extremely fine abrasives can produce highly smooth surfaces. This technique is also char- acterized by high precision and efficiency that are attributable to the metal bonding of the abrasive. 6.5.3 Surface Modifying Effect by ELID Grinding In order to verify the surface modifying effect at the top of the substrates on which ELID grinding was applied, the hardness was tested using a FIGURE 6.22 ELID ground AlN. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 168 6.10.2006 2:18am 168 Handbook of Advanced Ceramics Machining 10 m 10 µm 10 m µm 10 µm #325 10 m 10 µm 10 m µm 10 µm #600 (a) (b) FIGURE 6.23 SEM images of ground surface by ELID. (continued ) Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 169 6.10.2006 2:18am Electrolytic In-Process Dressing Grinding of Ceramic Materials 169 10 m 10 µm 10 m µm 10 m 10 µm 10 m µm 10 µm 10 µm #1200 #2000 (c) (d) FIGURE 6.23 (continued) Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 170 6.10.2006 2:18am 170 Handbook of Advanced Ceramics Machining 10 m 10µ m 10 m m 10 m 10 µm 10 m µm 10 µm 10 µm #4000 #8000 (e) (f) FIGURE 6.23 (continued) Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 171 6.10.2006 2:18am Electrolytic In-Process Dressing Grinding of Ceramic Materials 171 nanoindenter. The maximum indentation load was set to 2 mN. Figure 6.25 shows the results of calculating the Vickers hardness of the top surface, from the relationship between the indentation load and the indentation depth. The resulting value indicates that the hardness of the ELID series is approximately 400 HV higher than that of the polished series. Consequently, it was found that 10 µmµm 10 µm #30000( g ) FIGURE 6.23 (continued) #325 #600 #1200 #2000 #4000 #8000 #300000 Mesh size of g rindin g wheel Br Ductile mode Transition area Brittle mode FIGURE 6.24 Relation between wheel mesh size and removal mechanism. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 172 6.10.2006 2:18am 172 Handbook of Advanced Ceramics Machining implementing ELID grinding on AlN produces a surface modifying effect that enhances the hardness of the top surface of the workpiece. Figure 6.26 shows the relationship between the frictional coefficient m and the number of sliding cycles, with respect to the results of the friction and wear testing. The testing conditions were as follows: . Load: 200 g . Diameter of opposite material (alumina ball): 3.175 mm . Sliding distance: 10 mm . Testing speed: 5 mm=sec . Number of tests: 100 times The results indicate that the frictional coefficient m of the ELID series is lower than that of the polished series. The high-quality surface hardness, as shown in Figure 6.25, obtained as a result of the surface modifying effect due to ELID grinding may be one of the reasons why the sliding character- istics are improved. 0 500 1000 1500 2000 2500 ELID series Polished series Vickers hardness HV FIGURE 6.25 Results of hardness measurements using a nanoindenter. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 173 6.10.2006 2:18am Electrolytic In-Process Dressing Grinding of Ceramic Materials 173 6.5.4 Analysis of the Modified Surface The properties of the machined AlN surface were analyzed by chemical element analysis using Auger electron spectroscopy. Figure 6.27 shows the results of this analysis. With respect to the intensity of oxygen atoms, the peaks of the ELID series are sharper than those of the polished series. Figure 6.28 shows the results of elemental analysis in the depth direction for various test material surfaces using x-ray photoelectron spectroscopy (XPS). The etching rate was set at 5 nm=min. With respect to the state of diffusion in the depth direction of the oxygen element, the ELID series maintains a higher peak than the polished series, suggesting that the in- crease in surface hardness shown in Figure 6.25 is caused by the oxygen diffusion phenomenon demonstrated here. As shown in Figure 6.26, ELID grinding yields superior tribological properties in the early stage of trib- ology testing, by virtue of not only the highly smooth surface attained, but also the resulting oxygen element diffusion layer. The ELID grinding method can be used to fabricate machined surfaces exhibiting desirable characteristics for hard AlN ceramics. Further experiments are planned in order to clarify the details of the diffusion mechanism of the oxygen element and determine the optimum processing conditions for ELID, such as the type of abrasive, the feed rate, and the machining fluid. According to the above-mentioned experimental results, the final finish- ing using a #30000 wheel produced an extremely smooth ground surface 0 020 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 40 60 80 100 Polished series Number of cycles, N Friction coefficient, m ELID series 0. 2N 5mm/ s Wo rk Al 2 O 3 ba ll 0.2 N 5 mm/sec Work Al 2 O 3 ball FIGURE 6.26 Relation between the frictional coefficient m and the number of sliding cycles. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 174 6.10.2006 2:18am 174 Handbook of Advanced Ceramics Machining roughness of 0.008 mm R a . In addition, the ELID series demonstrated surface hardness and sliding characteristics that were superior to those of the polished series. These advantages may be attributable to the diffusion phenomenon of the oxygen element produced by the ELID grinding. 500 1000 1500 2000 2500 80 85 90 95 100 105 Counts/sec Binding energy, eV Peak of oxyge n Peak of oxygen (a) ELID series 500 1000 1500 2000 2500 3000 80 85 90 95 100 105 Counts/sec Binding energy, eV (b) Polished series FIGURE 6.27 Results of analysis via Auger electron spectroscopy. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 3837_C006 Final Proof page 175 6.10.2006 2:18am Electrolytic In-Process Dressing Grinding of Ceramic Materials 175 [...]... Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C006 Final Proof 178 page 178 6.10.2006 2:18am Handbook of Advanced Ceramics Machining grinding wheels for precision grinding structural ceramics, Proceedings of the International Conference on Precision Engineering, Taipei, Taiwan, 19 97, pp 559–564 ¨ ¨ 24 Kampfe, A., Eigenmann, B., and Lohe, D., Advanced X-ray analysis of grinding residual... wheels, Annals of the CIRP, Vol 41, No 1, 1995, pp 2 87 290 Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C006 Final Proof Electrolytic In-Process Dressing Grinding of Ceramic Materials page 177 6.10.2006 2:18am 177 5 Ohmori, H., Takahashi, I., and Bandyopadhyay, B.P., Ultra precision grinding of structural ceramics by electrolytic in-process dressing (ELID) grinding, Journal of Materials... levels: 149.1, 174 .0, 198.9, 223.5, and 248.4 The fixed parameters were Regulating Wheel tilt angle: 38 Set depth of cut: 30 mm Љ Љ 2 2 12 12 12 101.2 FIGURE 7. 2 Al2O3 sample, showing the location of the six points where the diameter was measured Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C0 07 Final Proof page 184 2.10.2006 6:13pm Handbook of Advanced Ceramics Machining 184 Thus,... of cut vs feed and belt speed (b) Contour bands for several values of the depth of cut (c) Depth of cut vs feed for each of the used belt speeds The sample coefficient of determination, R2, is also shown (d) Depth of cut vs belt speed for each of the used feeds The sample coefficient of determination, R2, is also shown Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C0 07 Final Proof... the set depth of cut, we increase this pressure The resulting depth of cut is, therefore, a combination of the work parameters (speed and feed), Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C0 07 Final Proof page 188 Handbook of Advanced Ceramics Machining 188 6 6 Matrial removal rate (cm3/min) 240 6 5.5 230 5.5 220 5 5 5 210 4 5 200 4.5 4 190 180 250 3.5 40 30 45 3.5 170 50 150 Work... glass 179 Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C0 07 Final Proof page 180 180 2.10.2006 6:13pm Handbook of Advanced Ceramics Machining High-speed stock removal is made possible through technological advances of the three main raw materials that comprise the coated abrasive belts Minerals, backings, and adhesive bonds are the three raw materials that encompass the manufacture of. .. Al2O3, Proceedings of European Conference on Residual Stresses, Vol 6, No 2, 1999, pp 27 28 25 Hoshina, T., Tatami J., Meguro T., Komeya, K., Tsuge, A., Kuibira, A., and Nakata, H., Effect of coarser grains on sintering of AlN, Key Engineering Materials, Vol 2 47, 2003, pp 87 90 Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C0 07 Final Proof page 179 2.10.2006 6:13pm 7 High-Efficiency... presented in Figure 7. 7a, through Figure 7. 7d Theoretically, the stock removal is directly proportional with the depth of cut To confirm Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C0 07 Final Proof page 189 High-Efficiency Belt Centerless Grinding of Ceramic Materials 2 .75 Roughness (µm) 220 2.6 210 2.5 2.55 2 2.5 1.5 250 2.45 200 Feed (cm/min) 45 150 30 50 180 170 2.35 150 2.9 Surface... monitoring of the surface damage and integrity of ceramics in-process AE technology has been recognized internationally as one of the most promising in-process abrasive machining damage detection and monitoring method 193 Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C008 Final Proof page 194 6.10.2006 2:20am Handbook of Advanced Ceramics Machining 194 The lapping process is a very complex...Ioan D Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C006 Final Proof page 176 6.10.2006 2:18am Handbook of Advanced Ceramics Machining 176 16 14 ELID series Atomic percent, % 12 Polished series 10 8 6 4 2 0 0 2000 4000 6000 8000 10000 12000 14000 16000 Etching time, sec FIGURE 6.28 Results of elemental analysis carried out using XPS Acknowledgments . number of sliding cycles. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C006 Final Proof page 174 6.10.2006 2:18am 174 Handbook of Advanced Ceramics Machining roughness of 0.008. 6.28 Results of elemental analysis carried out using XPS. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C006 Final Proof page 176 6.10.2006 2:18am 176 Handbook of Advanced Ceramics Machining 5 sintering of AlN, Key Engineering Materials, Vol. 2 47, 2003, pp. 87 90. Ioan D. Marinescu / Handbook of Advanced Ceramics Machining 38 37_ C006 Final Proof page 178 6.10.2006 2:18am 178 Handbook of Advanced