PSI - Issue 36

Pavlo Prysyazhnyuk et al. / Procedia Structural Integrity 36 (2022) 130–136 Pavlo Prysyazhnyuk et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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of the hardfaced layers obtained by using experimental electrode material (EMH) as well as the serial one (OK13MN, ESAB production) are listed in Table 1.

Table. Typical chemical composition of the hardfaced layers in wt. %. С Si Mn Mo Ti Nb V EMH 3.2 3.0 11.5 7.0 3.6 6.9 3.8 OK 13MN 1.0 0.7 12.2 - - - -

The FCAW parameters were chosen based on the results of preliminary calculation of the temperature distribution over the heat affected zone and the welding thermal cycles, according to the recommendations reported in (Tatsiy et al. (2019), Duryahina et al. (2007)) aiming to obtain a single-phase austenitic matrix structure by avoiding cementite formation. So, the hardfacings were deposited on a mild carbon steel substrate of St.3 grade using following parameters: welding current – 180 A, voltage – 30 V, polarity – reverse. Hardfaced samples with sizes of 20×20×10 mm were cut from the welded specimens for microstructure and wear resistance investigations. For comparison study the steel samples with the same dimensions (HSS and mild carbon St. 45 steel) were used. Impact-abrasion wear tests were carried out using testing machine (Fig. 1) consisting of cam mechanism, that provides lift of the tungsten cemented carbide-tipped striker and its free fall followed by hitting the sample, which was fixed in sample holder containing abrasive particles. Chilled white cast iron particles with irregular shape and average size of 1 mm were used as an abrasive environment. The specific energy of impact was 2.4 J/cm 2 and testing time for each sample was set to 2 hours. Microstructure investigations were performed using scanning electron microscopy (SEM) together with energy-dispersive X-ray spectroscopy (EDS) at the cross-sectional areas as well as at the worn surfaces after impact-abrasion wear tests. The hardness of high-manganese steel-based hardfacings was measured by Rockwell method scale “C”. Before hardness measurements top lay ers were deformed using indentation of cemented carbide ball with diameter of 10 mm into surfaces at the load of 3000 N.

Fig. 1. Testing machine for impact-abrasion wear investigation

3. Results and discussion The results of the microstructural and chemical analysis of the fusion zone between EMH hardfacing and base metal are shown in Fig. 2. As can be seen from Fig. 2, the interface has smooth transition from the substrate to the coating and no defects such as pores, cracks, delamination zones, etc. were observed, that indicates strong metallurgical bonding. Results of the line scan chemical analysis across base metal – coating interface, show the presence of strong intensity peaks for the carbide-forming elements in the same coordinates, corresponding to the