PSI - Issue 20

Borisova M.Z. et al. / Procedia Structural Integrity 20 (2019) 48–52 Borisova M.Z. et al. / StructuralIntegrity Procedia 00 (2019) 000 – 000

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1. Introduction Different methods are used for working surface treatment in order to extending the life of machine details subjected to wear. One of the most effective methods is the deposition of flux-cored wires, see Student et al. (1994) or Li et al. (2014) or Shapovalov et al. (2017) or Zhang et al. (2019). Deposition of coatings from the Fe – Cr system is used extensively for protection from wear, increase the strength and hardness of the treated surfaces. The use of flux-cored wires makes it possible to vary widely the composition of the sprayed coatings. In addition, these coatings have high resistance to wear by Vinokurov et al (2009, 2011). Heating of the powder material during arc metallization is carried out due to the heat released as a result of the influence of electric current between the wire elements. Arc metallization is a procedure of layer-by-layer application to heated metal products of small thickness. The height of the electric arc is minimal, and the molten wire is dispersed by a gas flow directed along the axis of the filler material. Various additives are used to improve the quality of the coating. Corundum particles were used as a strengthening additive in the present study, Al 2 O 3 particles exhibit high hardness, wear resistance and thermal stability. The aim of this study was to investigate the influence of the arc metallization on the microstructure of the wire sprayed coatings. Meanwhile, the content of the corundum in the obtained coatings depending on the current As a research material, a FeCr cored wire with refractory additives of corundum Al 2 O 3 by Bolotina N.P. et al. (1995) was chosen. The cored wire with a diameter of 2 mm was manufactured by EDU-500 equipment at Scientific and Production Co. Ltd, "VEKHA-1" (Komsomolsk-on-Amur, Russia). The outer shell of wire was stainless steel. The filling material was mixed of ferrochrome and aluminum oxide powders with the following composition, % wt.: C ~0,47 – 0.51; Cr ~2 – 4; Al 2 O 3 ~10 – 15; Fe – other. The entry of ferrochrome and aluminum oxides increases the hardness and strength of wear-resistant coatings, see Lin et al. (2014) or Yasir et al. (2015) or Guo et al. (2016). The filling factor of the cored wires was 31% . The coatings were applied to the side surface of the wear test discs with a diameter of 50 mm and height of 10 mm with the help of an industrial electric arc metallization unit EDU-500C under the technological conditions listed in Table 1 with the deposition distance of 130 mm. The microstructure of powder coatings obtained after different technological modes was studied using AXIO Observer D1m "Carl Zeiss Microscopy GmbH" optical microscope. The morphology of coatings were observed by using scanning electron microscope (SEM, HITACHI TM 3030) equipped with the EDS analyzer (XFlash 6 "Bruker"). strength were investigated. 2. Materials and methods

Table 1. Technological modes of electric arc metallization.

Arc voltage U ( B )

Current strength I ( A )

№

1 2 3

30 30 30

220-250 250-280 280-300

3. Results and discussion A flux-cored wire is a hollow metal tube containing a powder material (Fig. 1). According to Bolotina N.P. et al. (1995), the filling factor of the flux-cored wire is 31%. Particles of refractory modifying additives of aluminum oxide have a size of ~40 – 100 μm , the particle size of the powder material is ~40 – 100 μm . The calculation of the volume fraction of Al 2 O 3 ( C )was carried out according to equation (1), where R, r – external and internal radiuses of the powder wire, θ – relative density of the powder material, ρ Al2O3 , ρ Fe С r – density of corundum and ferrochrome, k – their mass ratio in the powder wire.