PSI - Issue 20

Fedorov M. V. et al. / Procedia Structural Integrity 20 (2019) 206–211 Fedorov M. V. et al / Structural Integrity Procedia 00 (2019) 000–000

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Table 1. The percentage of ultrafine additives in tungsten-cobalt hard alloy. Specimen name MgAl2O4 (%) SiC (%) No. 0 - - No. 1 0.1 - No. 2 0.3 - No. 3 0.5 - No. 4 0.8 - No. 5 1.0 - No. 6 - 0.1 No. 7 - 0.2

Experiments on impact-abrasive tests for specimen were carried out close to natural conditions. Experimental plates were fixed in the working elements of tools operating under impact-abrasive loads. The operating principle of the device is that the specimen moves free along a fixed contour with constant speed then hits the granite counterbody and then moves along granite counterbody back to the starting position. Technical characteristics of the device: the electric motor power is 180 W, the electric motor rotation speed is 60 sec -1 , the impact energy is 24 J, the dry friction load is 12 N, the collision frequency is 1.5 sec -1 . Microanalysis of the fracture surface was carried out by a polarizing microscope Altami POLAR. Every five minutes after the impact-abrasive loads, a photo of the cutting edge of the test specimens was recorded in accordance with the scheme shown in Fig. 1b with magnification x30. The test specimens were symbolically divided into two faces of research of the cutting edge, designated by us as ”A” and ”B” and into three regions in each face: ”left edge”, ”center”, ”right edge”, see Fig. 1b. Fractographic studies were carry out on a Jeol JSM-6480LV electron scanning microscope. Results and Discussions It is known that the operating tools in impact-abrasive wear, tools undergo wear from mechanical impact and from thermal impact in the contact zone. Hard alloy materials under the action of impact loads, as a rule, are subject to brittle fracture. This is due to the main property of the hard alloy material - high hardness. Nikolenko et al. (2018); Saito et al. (2006); Allen et al. (2001); Shipway and Hogg (2005); Multanov (2002); Smirnov et al. (2007) showed that the influence on the structure of hard alloy materials by modifying, alloying and other methods leads to structure change by regulating the growth of grains that form the skeleton of hard alloys. The fracture surface macrographs of the specimen No. 0 are shown as example in Fig. 2. Macrographs were made every 5 min. The face of the cutting edge before the tests in the initial state is rough and not straight as shown in Fig. 2a. After testing after 5 minutes, smoothing of the cutting edge is observed as shown in Fig. 2b, smoothing is explained by the run-in stage. Subsequently, after 5 minutes, steady wear takes place as shown in Fig. 2c and Fig. 2d. Analysis of The fracture of the surface is characterized by slight deformation and a slight change in the height of the cutting edges.

Fig. 2. The process of the cutting edge hard-alloy plate fracture in impact-abrasive wear; specimen No. 0