PSI - Issue 36

Valerii Peremitko et al. / Procedia Structural Integrity 36 (2022) 106–113 Valerii Peremitko et al. / StructuralIntegrity Procedia 00 (2021) 000 – 000

107

2

n c

number of cracks (taking into account the weighting factor)

1. Introduction High-alloy white cast irons that occupy one of the leading places among cast irons with special properties are used for the production of parts working in the conditions of abrasive and hydro abrasive wear discussed by Sm rkovský (1999), Sare (1998). In international and domestic practice great experience in the use of optimally alloyed high-chromium and chromium-manganese cast irons as wear-resistant materials has been accumulated discussed by Yüksel (2014), Studnicki (2006). However, such cast irons do not always meet the necessary requirements for wear resistance and mechanical properties. They are prone to the formation of cracks and pores in the process of their application by arc surfacing, hardening or heat treatment. Analysis of literature sources concerning this problem shows that the improvement of technological and operational properties of chromium-manganese cast iron can be reached by additional alloying, microalloying, modification and testing of all technological process operations for manufacturing the blanks and finished products using bimetallic sheets discussed by Coronado (2009), Liu (2008), Peremitko (2014), Babinets (2017). Operational and mechanical properties of white wear-resistant cast irons are determined by the number, size, shape of carbides, base structure and their microhardness discussed by Albertin (2001), Tang (2011), Coronado (2011). The plastic properties of these materials decrease in the case with a large number of carbide phases. Taking into account that in addition to chromium and manganese, silicon is also carbide-forming agent in cast irons, and is worth determining the optimal concentrations of these elements in white cast irons in order to obtain maximum hardness and wear resistance discussed by Efremenko (2018). In particular, silicon in high-chromium cast iron is distributed between austenite and eutectic melt during crystallization discussed by Azimi G. (2010). This element causes the increase in temperature of eutectic crystallization, expands the interval of eutectic transformation, weakens the effect of the cooling rate. The hardness and wear resistance of the material increase in proportion to the silicon content within Si = 0. 05…0 .78% range. The decrease in harden ability of high-chromium cast iron with the increase in the amount of silicon and carbon is recorded. The positive experience of modifying high-chromium cast iron with such rare-earth elements as titanium and aluminum discussed by Liu D. (2013), Han-guang Fu (2009) is also known. As the result, the size of eutectic carbides and non-metallic inclusions in the cast iron is changed, sulfur is removed, and cast grain is crushed. The objective of the work is to determine the optimal concentrations of individual alloying elements in surfacing materials in order to reduce defects (cracks and pores) in the applied layers and, as a consequence, increase their service life. 2. Statement of the objectives The case of application the layers, which correspond to wear-resistant 450Kh30M and 500Kh22B7 cast irons in composition, on 6 mm thick St3 steel samples was considered in the work. In order to determine the influence of silicon and aluminum content in the original surfacing materials on the quality, hardness of the surfaced layers, as well as the development of mathematical models, a number of experiments were conducted. Wires and tapes were used as surfacing materials providing variation of alloying elements content in a wide range of the applied layer: PLAN-T 201powder tape (PL-Np-450X30-B-C) with 10 and 16 mm width, Veltek N-630-O powder wires (composition in th e second layer 460Х24 -B) with 1.6 and 2.0 mm diameter and UTP SK-256- О (550Х27) with 1.6 mm diameter. Table 1 shows the chemical composition determined by the manufacturers for the material of samples and pure surfacing selected as surfacing materials in the copper mold. The controlled parameters (response) are: maximum and minimum hardness on the cross section of the surfaced layer, maximum and minimum hardness on the surface of the surfaced layer, the number of pores and the number of cracks. In order to bring the effect of crack opening on the efficiency of the surfaced layer to a single indicator, the