## 4 Discussion  
With the increasing pressure, the friction coefficient of the 15% SCF-modified bearing bush initially decreases and then experiences an increase from 0.420 to 0.296 and then to 0.326. Compared with the PEEK and carbon fiber-modified composite developed by [PERSON] et al. (2019), the average friction coefficient of the PEEK material exhibits an initial increase followed by a decrease as the applied load increases. The loads applied at 75 N, 100 N, and 125 N are much lower than those used in this test. Nonetheless, the material exhibits a frictional morphology that aligns with the characteristics of the low speed and heavy load conditions, suggesting that the 15% SCF-modified bearing bush is indeed capable of functioning effectively under heavy load conditions. Under dry friction conditions, when the load reaches the critical value, the friction heat on the surface can reach the softening point of the material or cause the surface oxide film to break, leading to a transition in the wear rate. The wear mechanism of SCF/PEEK composites under these conditions is primarily characterized by adhesive wear and slight abrasive wear. In contrast to the analysis by [PERSON] et al. [18] on the friction and wear performance of 20% CF/PEEK composites at high temperatures, this paper integrates the lubrication and cooling properties of lubricating oil to substantially mitigate the detrimental effects of frictional heat on self-lubricating materials. This approach effectively curbs the plastic deformation, adhesion, and fiber shedding induced by frictional heat within the composites, thereby enhancing their performance under high-temperature conditions. Consequently, the influence of friction heat on the friction and wear performance of self-lubricating materials is not discussed in this paper. Moreover, the lubricating oil effectively removes wear debris between the friction surfaces, preventing its accumulation on the worn surface, which would either impair or hinder the formation of a transfer film. However, it should be noted that while preventing the formation of transfer film, the lubricating oil concurrently generates a certain level of lubrication between the interacting surfaces, thereby reducing system friction and aiding in material wear reduction. The load exerts a significant impact on the physical transformation processes occurring within the surface layer of self-lubricating materials. This is due to the fact that the magnitude of the load directly alters the size of the actual contact area on the friction surface, subsequently influencing the temperature of the surface layer and the progression of wear during the friction and wear process. Under oil lubrication, the wear surface of SCF/PEEK-modified materials exhibits a discernible thinning and smoothing of fibers, which is a clear indication of effective interfacial bonding between the SCF and the matrix. SCF not only assumes a crucial bearing function during the friction process but also prevents the surface micro-convex from cutting the composite matrix. The presence of interfacial gaps between the SCF facilitates the flow of lubricating oil, thus contributing to a lubrication effect that aids in reducing friction between the interacting surfaces. Based on the EDS (Energy Dispersive Spectroscopy) spectrum analysis, it can be observed that fiber fracturing occurs in the friction morphology of the 15% SCF/PEEK self-lubricating bearing bush under the load of 15 MPa. The observed phenomenon resembles that of fiber stripping and complete pulling out, which is associated with the interfacial bonding strength between the fiber and the resin matrix. The interfacial bond strength is also related to the treatment of the fibers. Currently, the prevalent treatment methods available in the market include oxidative treatment, surface coating, plasma surface modification, chemical grafting, and nanoparticle modification, among which the treatment method employed in this text for carbon fiber is oxidative treatment [36].