In this study, the performance against erosive wear of PVD TiN (titanium nitride) coating was evaluated using an erosion test rig similar to that described in the standard ASTM G76-95. This coating normally has variou...In this study, the performance against erosive wear of PVD TiN (titanium nitride) coating was evaluated using an erosion test rig similar to that described in the standard ASTM G76-95. This coating normally has various industrial applications such as tapping, drilling, dry machining and punching. Angular silicon carbide (SiC) was used as an abrasive particle with a grain size of 350-450 μm. Erosion tests were carried out using different incident angles, 30°, 45°, 60° and 90° with a particle velocity of 24 ± 2 m/s, an abrasive flow rate of 0.7 ± 0.5 g/min, and the test temperature was between 35°C and 40°C. The particle velocity and the abrasive flow rate were low in all of the tests to reduce the interaction between the incident and the rebounding particles in the system. The surfaces were examined with a scanning electron microscope (SEM) to characterize the erosive damage. The wear mechanisms identified were brittle fracture characterized by radial cracks on the surface by multiple impact and a few pits at 30°, while a few cracks and the formation of craters in random positions were observed at angles near or at 90°. Elliptical scars were observed at 30° and 45°, which are a characteristic feature when the specimens are impacted at low-incident angles (α ≤ 45°) whereas a roughly circular scar was seen at 60° and 90°. In addition, roughness variations were analyzed using atomic force microscopy (AFM), before and after the erosion tests, and the results exhibited an increase in the roughness as the TiN samples were impacted at angles near or at 90°.展开更多
The erosion wear behaviour and mechanism of several middle temperature seal coatings were investigated by a CMS 100 self made vacuum sand erosion machine. The results show that the relationship between the erosion mas...The erosion wear behaviour and mechanism of several middle temperature seal coatings were investigated by a CMS 100 self made vacuum sand erosion machine. The results show that the relationship between the erosion mass loss and the erosion time is linear, the coatings hold a maximum erosion rate at 60° impact angle, and the relationship between the erosion rate and the impact speed is an exponential function. The speed exponent increases with the increase of the impact angle. At 90° impact, indentations and extruded lips were generated on the coating surface subjected to impact. With repetitive impact by the abrasive particles, the extruded lips were work hardened and peeled off, while flattened metal phase grains were impacted repeatedly, loosed and debonded. At 30° impact, the erosion wear of the coating is characterized by micro cutting, plowing and tunneling via pores and non metal phase. The model of the erosion mechanism is advanced on the basis of the above mentioned erosion wear behaviour.展开更多
文摘In this study, the performance against erosive wear of PVD TiN (titanium nitride) coating was evaluated using an erosion test rig similar to that described in the standard ASTM G76-95. This coating normally has various industrial applications such as tapping, drilling, dry machining and punching. Angular silicon carbide (SiC) was used as an abrasive particle with a grain size of 350-450 μm. Erosion tests were carried out using different incident angles, 30°, 45°, 60° and 90° with a particle velocity of 24 ± 2 m/s, an abrasive flow rate of 0.7 ± 0.5 g/min, and the test temperature was between 35°C and 40°C. The particle velocity and the abrasive flow rate were low in all of the tests to reduce the interaction between the incident and the rebounding particles in the system. The surfaces were examined with a scanning electron microscope (SEM) to characterize the erosive damage. The wear mechanisms identified were brittle fracture characterized by radial cracks on the surface by multiple impact and a few pits at 30°, while a few cracks and the formation of craters in random positions were observed at angles near or at 90°. Elliptical scars were observed at 30° and 45°, which are a characteristic feature when the specimens are impacted at low-incident angles (α ≤ 45°) whereas a roughly circular scar was seen at 60° and 90°. In addition, roughness variations were analyzed using atomic force microscopy (AFM), before and after the erosion tests, and the results exhibited an increase in the roughness as the TiN samples were impacted at angles near or at 90°.
文摘The erosion wear behaviour and mechanism of several middle temperature seal coatings were investigated by a CMS 100 self made vacuum sand erosion machine. The results show that the relationship between the erosion mass loss and the erosion time is linear, the coatings hold a maximum erosion rate at 60° impact angle, and the relationship between the erosion rate and the impact speed is an exponential function. The speed exponent increases with the increase of the impact angle. At 90° impact, indentations and extruded lips were generated on the coating surface subjected to impact. With repetitive impact by the abrasive particles, the extruded lips were work hardened and peeled off, while flattened metal phase grains were impacted repeatedly, loosed and debonded. At 30° impact, the erosion wear of the coating is characterized by micro cutting, plowing and tunneling via pores and non metal phase. The model of the erosion mechanism is advanced on the basis of the above mentioned erosion wear behaviour.
