OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 2 2023 Ta b l e 2 Electron microprobe analysis of coatings Area, No. Chemical element, wt. % W Co C Cr 1 92.84 2.89 3.52 0.74 2 87.69 3.28 8.23 0.8 3 80.59 7.95 7.45 4.0 4 79.17 9.08 6.83 4.91 5 77.65 10.52 7.87 3.95 Fig. 5. Microhardness of coatings formed by different modes Fig. 6. Relative wear resistance of coatings formed by different modes Mechanical properties and wear resistance of WC-Co coatings The results of measurements of the coatings microhardness average values depending on the spraying mode are shown in Figs. 5. An increase in the arc current contributes to a decrease in the microhardness values, which can be explained by a decrease in the volume fraction of carbides in the coatings. The influence of the spraying distance is insignificant, while the hardness of the coatings obtained by spraying from a distance of 250 mm is slightly lower. The maximum microhardness (1,284 and 1,287 HV0.1) is typical for coatings obtained using the 170/140 and 250/140 modes. The lowest values of microhardness (1,153 and 1,140 HV0.1) are specific to coatings obtained using 170/200 and 250/200 modes. On the average, the microhardness of carbides is 1,432 ± 107 HV0.1, while that of the cobalt matrix is 772 ± 93 HV0.1. The obtained data are in good agreement with the data of [9, 25]. Fig. 6 shows the results of testing coatings for wear with abrasive particles. According the obtained data, the maximum wear resistance is typical for samples with cermet coatings obtained by 170/140 mode (relative wear resistance – 0.21), the minimum wear resistance is characterized for samples obtained by 250/200 mode (relative wear resistance – 0.14). The decrease in wear resistance can be explained by a decrease in the volume fraction of the carbide phase, which is in a good agreement with the results of microhardness measurements. To evaluate the adhesion of the coatings, 180° bend tests were carried out in the work. In all cases, the coatings cracked in the bending area, but did not peel off. Fig. 7 shows images of the surface of plates with coatings obtained by modes 170/140 (Fig. 7, a) and 250/200 (Fig. 7, b) after testing. It can be seen
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