636 M. Hadad et al./ Wear 260(2006)634-641 ative humidity during testing of 20-40%RH, sliding distance an increase of Tin content in the matrix, e.g. Si3N4-30% 36 m and ambient temperature Tin revealed three times higher wear resistance than bulk The same tribological tests were performed at 300C Si3N4 only on Si3N4 bulk and Si3N4+30% TIN composite. Before and after each experiment, the specimens were cleaned and 3.1.1. The influence of the sliding directions on wear weighed. The cleaning process consisted of: (a) soaking the resistance specimens in acetone for 5 min, (b)in subsequent treatment Transversal sliding shows the highest wear resistance. In in an ultrasonic bath of acetone and alcohol for 5 min,(c) some cases the wear resistance is a factor three times higher Immersion the spe ecimens in alcohol for 5 min and d)drying compared to sliding on the outer layer as shown in Fig 2b the specimens under cold air for 5 min This difference in wear resistance is due to the tin containing The worn surfaces and wear debris were investigated in the inner layer with an optical profilometer and a scanning electron micro- scope(SEM). The SEM(LEO DSM 962)is equipped with 3. 1.2. The influence of the difference in laminates on the an energy dispersive X-ray spectrometer(EDS) for elemen- wear resistance tal analysis (Voyager 4, Noran Instrument, Liquid nitrogen With respect to the sliding directions(Fig 2b) and com- cooled Si(Li) detector). The EDS working conditions were a paring among all laminates, laminates 30 shows the highest take-off angle 35, working distance to the specimen 25 mm wear resistance, which could confirm the improvement of and accelerating voltage of 15 kV. We used EDS to analyse wear resistance by adding TiN. On the other hand, comparing the worn surface and wear particles. In this case, our EDs between laminates 20 and 10. the difference in wear resis- analysis delivers only semi-quantitative results as we anal tance could be within the experimental scatter. yse non-planar surfaces and light elements like oxygen. Also EDS reveals only information on compositions from the outer 3. 1.3. Comparison between laminates and composites surface as the beam penetrates only a certain depth into the materials sample surface, which is in our experimental conditions in Despite the high scatter, a comparison between laminates nge of 1-2 um de and composites materials is possible, in the case of laminate 30 compared to Si3N4-30% TiN composite and laminate 10 compared to Si3N4-10%TIN composite, laminates subjected 3. Results and discussion to transversal or longitudinal sliding solicitation show that the wear resistance of those laminates and composites was 3. Wear rate similar. On the other hand. laminate 20 shows lower wear resistance compared to Si3N4-20% TiN composite Slid- Each determined wear rate is an average value from ng on the outer layer shows also a lower wear resistance three wear tests. Fig. 2a shows the measured wear rates of than bulk materials. This may be attributed to the presence bulk and composites. The wear resistance increased with of porosity within the layer. Wear is found to be produced C Laminates 10 Laminates 20 5a Laminates 30 20E-04 20E04 口S3N4+10%TN 冒15E04 圈siN4+20%TN 15E04 g10E04 50E05 5.0E-05 Fig. 2. Wear rate results: (a)composites and bulk and (b) laminates with a schematic presentation of sliding direction636 M. Hadad et al. / Wear 260 (2006) 634–641 ative humidity during testing of 20–40% RH, sliding distance 36 m and ambient temperature. The same tribological tests were performed at 300 ◦C only on Si3N4 bulk and Si3N4 + 30% TiN composite. Before and after each experiment, the specimens were cleaned and weighed. The cleaning process consisted of: (a) soaking the specimens in acetone for 5 min, (b) in subsequent treatment in an ultrasonic bath of acetone and alcohol for 5 min, (c) immersion the specimens in alcohol for 5 min and (d) drying the specimens under cold air for 5 min. The worn surfaces and wear debris were investigated with an optical profilometer and a scanning electron micro￾scope (SEM). The SEM (LEO DSM 962) is equipped with an energy dispersive X-ray spectrometer (EDS) for elemen￾tal analysis (Voyager 4, Noran Instrument, Liquid nitrogen cooled Si(Li) detector). The EDS working conditions were a take-off angle 35◦, working distance to the specimen 25 mm and accelerating voltage of 15 kV. We used EDS to analyse the worn surface and wear particles. In this case, our EDS analysis delivers only semi-quantitative results as we anal￾yse non-planar surfaces and light elements like oxygen. Also EDS reveals only information on compositions from the outer surface as the beam penetrates only a certain depth into the sample surface, which is in our experimental conditions in the range of 1–2
m depth. 3. Results and discussion 3.1. Wear rate Each determined wear rate is an average value from three wear tests. Fig. 2a shows the measured wear rates of bulk and composites. The wear resistance increased with an increase of TiN content in the matrix, e.g. Si3N4–30% TiN revealed three times higher wear resistance than bulk Si3N4. 3.1.1. The influence of the sliding directions on wear resistance Transversal sliding shows the highest wear resistance. In some cases, the wear resistance is a factor three times higher compared to sliding on the outer layer as shown in Fig. 2b. This difference in wear resistance is due to the TiN containing in the inner layer. 3.1.2. The influence of the difference in laminates on the wear resistance With respect to the sliding directions (Fig. 2b) and com￾paring among all laminates, laminates 30 shows the highest wear resistance, which could confirm the improvement of wear resistance by adding TiN. On the other hand, comparing between laminates 20 and 10, the difference in wear resis￾tance could be within the experimental scatter. 3.1.3. Comparison between laminates and composites materials Despite the high scatter, a comparison between laminates and composites materials is possible, in the case of laminate 30 compared to Si3N4–30% TiN composite and laminate 10 compared to Si3N4–10% TiN composite, laminates subjected to transversal or longitudinal sliding solicitation show that the wear resistance of those laminates and composites was similar. On the other hand, laminate 20 shows lower wear resistance compared to Si3N4–20% TiN composite. Slid￾ing on the outer layer shows also a lower wear resistance than bulk materials. This may be attributed to the presence of porosity within the layer. Wear is found to be produced Fig. 2. Wear rate results: (a) composites and bulk and (b) laminates with a schematic presentation of sliding direction