Measurement of chemical and geometrical surface changes in a wear track by a confocal height sensor and confocal Raman spectroscopy

Geometrical and chemical changes in the wear track can cause a drift in friction level. In this paper, chemical and geometrical surface changes in wear tracks are analyzed. For this, a setup with a confocal height sensor was developed to measure the local height changes on the wear track, combined with confocal Raman spectroscopy to determine the chemical changes at the surfaces. Pin-on-disc experiments were performed at room temperature and at elevated temperature (600 °C) to understand the material behavior between mild and severe wear regimes. The wear tracks developing between the two ceramics, alumina (Al2O3) and zirconia (Y-TZP), were analyzed using these techniques. The results of confocal height sensor showed significantly more geometrical changes in surface roughness at 600 °C compared to the test conducted at room temperature. The developed roughness in the wear track was approximately 250 times larger at 600 °C due to the higher degradation of the mechanical properties of ceramic. Further, material transfer was observed for the test conducted at 600 °C using Raman Spectroscopy. Material transfer at room temperature is difficult to observe because surface changes are less evident in mild wear regimes. The results show that the changes in the micro-geometry of the surface and the chemical compositions of the surface influence the friction level and wear processes. The confocal height sensor and Raman Spectroscopy were used to measure and understand the geometrical and chemical changes occurring on the surface of a wear track during sliding in a single setup.