## 3 Results and Discussions
### Tribological Properties  
Figure 10 shows the trend of borided layer thickness and wear depth with different boriding temperatures after wear testing. As shown in Figure 10, with increasing boriding temperature, wear depth decreased, and thickness of the borided layer increased. It can be seen from Figure 10 that the wear depth of the treated sample was lower than that of the untreated sample. In addition, it was observed that the wear depth tended to decrease as the boriding temperature increased. It was due to the thickness of the hardened layer reducing the wear as the boriding temperature increased. The wear depth decreased gradually with the boriding temperature increasing. During the designed temperature range, when the boriding temperature increased to 1150 \({}^{\circ}\)C, the wear depth reached the minimum value of 3.02 \(\upmu\)m.  
Figure 11 shows the corresponding SEM micrographs, EDX analysis, and 2D profilometric view of the worn surfaces of the untreated and borided samples after wear testing, from which the wear depth and width values were determined. Figure 11a shows evidence of severe plastic deformation with heavy smearing on the worn surface of the untreated sample due to repeated force applied to the sample surface during wear testing. The observed scratches and grooves indicate abrasion effects. From 2D profiles showing the wear depths, it is clearly seen that boriding of Ti substantially improved its wear resistance under a 4.9 N loading force. A wide and deep wear track formed on the untreated sample during wear testing. A continuous wear track with an average depth of 58 \(\upmu\)m and a width of 1240 \(\upmu\)m was formed on the untreated sample. The rough 2D wear track seen in the  
Figure 10: Trend of borided layer thickness and wear depth with different boriding temperatures after wear testing. untreated sample was larger and deeper compared to those in the treated samples. It was due to severe plastic deformation with heavy smearing and scratches occuring on the surface of the untreated sample during wear testing. The wear depth can be calculated with Equation (1) by supposing that an abrasion partner ball was not worn. The results are shown in Table 7. As shown in Table 7, it was found that the wear depths of the borided samples were smaller than that of the untreated sample. It was due to the formation of a boride layer on the surface. The boride layer has  
Figure 11: SEM micrographs, EDX analysis, and 2D profilometric view of the surfaces of the (**a**) untreated sample and those prepared using boriding temperatures of (**b**) 950 \({}^{\circ}\)C, (**c**) 1050 \({}^{\circ}\)C, and (**d**) 1150 \({}^{\circ}\)C, after wear testing. high hardness and acts as a protective Ti substrate during wearing with the grinding ball. In addition, [PERSON] et al. also found that the wear of the treated sample by boriding is reduced [40]. The wear depth decreased gradually with increasing boriding temperature. Hence, the boriding of the pure Ti substrate substantially increased its wear resistance, consistent with the hardness measurements. The wear track of the sample borided at 950 \({}^{\circ}\)C was much deeper than those of the other borided samples, but slightly shallower than that of the untreated sample due to some increased hardening from the very thin boride layer. In this processing temperature, the binding force between the hardened layer and base material was low, and microparticles were removed from the surface during wear tests, producing the linear scratches observed in the wear scars (Figure 11b). At the boriding temperature of 1050 \({}^{\circ}\)C, the worn surface showed limited deformation and smearing effects, and the wear depth was significantly smaller than in the untreated and 950 \({}^{\circ}\)C samples, attributed to the formation of a sufficiently thick hardened layer.