OBRABOTKAMETALLOV TECHNOLOGY Vol. 26 No. 4 2024 fi lm, which is clearly observed in the wear track images of the PO1 material shown in Table 3. The better performance of the PO1 was also attributed to the FDM printing orientation direction angle (i.e. 0°). In addition, the PO1 material (as shown in Fig. 11) with a printing orientation angle of 0° showed excellent tensile and compressive strength, primarily because the printing orientation was aligned with the load application direction. In this position, the material layers have a constant thickness and a longer length in the PO1 direction, which is likely to improve the bonding between the material layers, ultimately reducing wear. In addition, in the case of PO2 and PO3 materials, the printing orientation angle was 45° and normal to the loading direction. The layer adhesion is aff ected by the load and heat generated during operation [14]. As a result, a stable transfer fi lm is not formed. This is also confi rmed by the wear track images for PO2 and PO3 materials shown in Table 3. In the case of PO2, an uneven transfer fi lm was observed, resulting in poor wear resistance. It should also be noted that the layer adhesion was poor in the specimens produced with a printing orientation angle of 30–60° [14, 26]. The schematic diagram of the printing orientation and direction of normal load acting on the pin during the test is shown in Fig. 11. The fi gure shows that in the case of PO2 material, the load acting on the pin is further divided into two components. The horizontal component tries to weaken the bonding between the layers, causing vibration in the system; and because of this a stable transfer fi lm is not formed, which leads to greater wear of PO2. In case of PO2, this phenomenon was not observed so the effi ciency of PO3 was higher than that of PO2. However, it should be noted that the bond strength is less in printing situation of PO3 compared to PO1, so its effi ciency is lower than that of PO1. The values of normal load and speed in the equation from Table 4 for materials PO1, PO2 and PO3 indicate that wear is more dependent on normal load than on sliding speed. In order to have a clear understanding of the infl uence of the input parameters on wear, 3-D graphs of wear were plotted using the empirical equation given in Table 4 varying with normal load and sliding speed. The 3-D surface curves were plotted by varying the two process parameters simultaneously while keeping the third parameter constant in the middle value of the parameter ranges as shown in Table 1. The 3-D graphs refl ecting the variation in the wear are shown in Fig. 12, a–c. Fig. 12, a, b, c depict the variation in the wear with the normal load and speed for PO1, PO2 and PO3 Fig. 11. Schematic diagram of the printing orientation and the direction of application of the normal load acting on the pin during testing a b Fig. 10. Eff ect of normal load at constant speed of 600 rpm (a) and eff ect of speed at constant normal load of 600 N (b) on wear behavior of PO1, PO2 and PO3 specimens
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