## 3 Results and Discussions
### Tribological Properties
The examination of the worn surface of the treated sample showed that there was no obvious plastic deformation, which was consistent with the extremely low wear rate. In addition, it can be seen from Figure 11 that some oxidative wear had occurred. This was due to the friction heat generated in wear testing, causing oxidation to occur. [PERSON] et al. also got the same result [41]. The surface pressure calculated from the wear width after wear testing of the untreated sample and those boriated at 950 \({}^{\circ}\)C, 1050 \({}^{\circ}\)C, and 1150 \({}^{\circ}\)C were 0.41, 0.44, 1.52, and 3.90 N/mm\({}^{2}\), respectively. The surface pressure of the untreated sample was lower than that of the boriated samples, and the surface pressure increased with increasing boriding temperature. This was the reason why wear width decreased with increasing boriding temperature (corresponding to higher hardness values) for the same applied force. The surface pressure values of the 950 \({}^{\circ}\)C treating sample and the untreated sample were of the same order of magnitude, indicating similar wear severity. This was attributed to the very thin hardened layer formed at this low boriding temperature. The different surface pressures observed for the samples prepared using different boriding temperatures are expected to affect the fricative values measured during the wear testing. Therefore, Figure 12 shows the fricative values as a function of time for all samples. With increasing wear testing time, the fricative value first increased and then decreased to a stable value. Over time, the actual contact area between the sample surface and the ZrO\({}_{2}\) ball increase under fixed positive pressure, and the elastic deformation of the contact surface increases, resulting in an increase in the fricative value. When contact time is extended beyond a certain critical time, the elastic and plastic deformation of the contact surface no longer increases. With increasing contact time, the wear and plastic deformation of the contact point changes the surface morphology and the pressure state of the sample. After a certain time, the maximum dynamic friction force saturates and the wear enters a stable stage, resulting in a stable fricative value. The average fricative values for the untreated sample and those boriated at 950 \({}^{\circ}\)C, 1050 \({}^{\circ}\)C, and 1150 \({}^{\circ}\)C were 99.1, 94.1, 88.9, and 93.2 dB, respectively. The fricative value of the untreated sample was higher than those of the boriated samples, indicating that boriding reduced the fricative value. The maximum fricative value was observed for the sample boriated at 950 \({}^{\circ}\)C, attributed to the thinner hardened layer that allowed the formation of particles via flaking, which wear with the sample and the grinding ball. The fricative value of the sample treated using a boriding temperature of 1050 \({}^{\circ}\)C was lower than that of the 1150 \({}^{\circ}\)C sample. The higher concentration of hard TiB\({}_{2}\) in the 1150 \({}^{\circ}\)C sample (as confirmed by XRD) resulted in lower elastic deformability during wear testing. Due to the high surface hardness of TiB\({}_{2}\), the hardened layer was brittle. It was due to the surface hardness reaching the maximum value at this processing temperature. The higher the surface hardness, the easier the brittle fracture occurs. It was due to the weakening of the elastic deformation ability of the sample. [PERSON] et al. also found that when the brittleness index is higher, elastic deformability is lower [42]. During wear testing, the sample deforms due to the absorption of mechanical energy. Brittle materials absorb less energy than soft ones during wear testing, resulting in larger vibrations and higher fricative values. The lowest fricative value was observed for the sample treated at a boriding temperature of 1050 \({}^{\circ}\)C due to the optimal ratio of TiB\({}_{2}\) to TiB. Hence, this material is considered suitable for practical use, as it will induce the least vibration under wear conditions.