*2.1. Nanocrystalline Layer Deposited with Covered Fe-Cr-Nb-B Electrode*

The Fe-Cr-Nb-B nanocrystalline layer, shown in Table 1, deposited by MMA with a 3.2 mm covered electrode on an S355N steel alloy substrate is shown in Figure 1. MMA deposit welding was performed with a constant direct current of 100 A in the flat position (PA). During welding, the electrode was set at an angle of 90◦ with respect to the surface of the welding base. The sheet surface was ground and pre-heated with a gas torch to a temperature of 80 ◦C.

**Table 1.** Chemical composition and hardness of the tested deposit weld.


**Figure 1.** Macrostructure of the cross-section of a nanocrystalline layer, the average width of the overlay layer is 3 mm.

According to the manufacturer s data, the Fe-Cr-Nb-B nanocrystalline alloy electrodes mostly consist of very hard boron carbide fractions evenly distributed in a semi-amorphous iron alloy matrix, yielding a hardness of 67–70 HRC. The deposit weld should have a high abrasion resistance and an increased resistance to dynamic loads due to these characteristics. The electrodes can be used for both direct- and alternating-current welding.
