PSI - Issue 53

Daniel R. Galán-Rivera et al. / Procedia Structural Integrity 53 (2024) 407–415 Daniel R. Galán-Rivera et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction With the current growth of the world population and its overcrowding in large cities, the development of efficient means of transportation that allows moving a great number of people is increasingly required. By 2050, it is estimated that 70% of the world´s population will be concentrated in large cities (Cho, 2018). Therefore, ways to anticipate problems, related to pollution, habitability and mobility in these mega populations are already being studied (Borck, 2019). This is where rail transport and, especially in these cities, the tram, take on greater importance every day. This means of transport allows moving many people with a lower environmental impact and greater compatibility with other means of transport (Martin et al., 2014). However, the growing increase in the use of the tram as a means of transport does not usually lead to an improvement in the existing railway infrastructure. Aspects of the track such as the old rails are maintained and, on them, we apply greater loads and greater traffic frequencies. This has an impact on the need to establish better maintenance of the track since aspects such as wear can be accelerated and have an impact on a reduction in the service life of the tramway (Galán-Rivera et al., 2020). The most widespread methods currently for repairing the track are the arc welding cladding methods (Mortazavian et al., 2020; Chen et al. 2020). These processes applied to the tram sector can present difficulties: due to the high thermal input values, excessive temperatures are generated in the rails that can degrade (or melt) the pieces attached to the rail that surround it (Sandor et al., 2013). Therefore, every day, new technologies for repairing this type of infrastructure are being studied (Tomlinson et al., 2023). Thanks to their versatility and the low impact on the base material, additive or layer manufacturing technologies are increasingly widespread in the sector (Lu, 2019; Lewis, 2012). One of the most promising technologies for rail repair is laser powder deposition (Mortazavian et al., 2022). Its use has already been extended to improve the properties of train wheels, the application of this process to the repair of tram rails can open endless possibilities in which the properties of the rails begin to be improved at the same time. that their defects are repaired (Ding et al., 2022). That is why in this work the application of different powder materials on rail steel has been studied in order to see the possibility of carrying out a correct repair of tram tracks. 2. Method 2.1. Specimen, material and equipment As a base material, a grade of steel called R260 has been chosen, which is widely used in the tramway world and whose properties are included in current regulations (CEN, 2019). R260 rail is a material with a high percentage of carbon (>0.6%), with a 100% pearlitic microstructure and does not follow any accelerated cooling thermal treatment to improve its properties (mechanical properties are related to chemical composition and practically constant in all sections of the rail) (ArcelorMittal, 2018) (Table 1). In order to simulate a defect in the rails due to wear, the rolling corner was milled with an angle of 45 degrees with a diagonal of the milling zone measure from 13 to 18 mm length (Fig. 1).

Table 1. Chemical composition and mechanical properties of R260 rail

Grade of steel % C

% Si

%Mn

%Cr

CE

Rm, MPa

As, %

Hardness, HB

R260

0.62-0.80 0.15-0.58 0.70-1.20

≤0.15

≈ 0.90 ≥ 880

≥ 10

260-300