**4. Conclusions**

The metallographic examinations of the materials selected for the tests did not show any internal or external defects in the layers formed by MMA welding with coated electrodes and GMA welding. Analysis of the test results of the obtained layers of arc-welded Fe-Cr-Nb-B-type alloy confirmed:


The ABRECOPLATE plate has a structure of white cast iron with chromium-molybdenum carbide precipitates. To join this plate with a low-carbon steel support plate, a soft binder was used on the copper matrix, which perfectly transfers the stresses occurring between the layers. In the case of CDP, the surface layer structure is a chromium cast iron containing many primary carbides.

The layer created with ABDADUR 64 coated electrodes possesses a eutectic iron structure with numerous precipitates of niobium and chromium carbides. The use of an austenitic steel buffer layer, in this case, allowed for crack avoidance that could propagate through to the substrate material. The layer formed by GMA surfacing with a ceramo-metallic wire is characterized by a nickel matrix containing many tungsten carbides. As a result of the thermal cycle, it can be observed that the WC carbides are partially dissolved, which may reduce the abrasion resistance of such layers.

HARDOX 400 is characterized by a tempered martensite structure. The hardness measurements carried out on the ground face of abrasion-resistant layers showed that all materials have a hardness similar to the hardness quoted by the manufacturers. The highest hardness on the surface is characterized by the nanocrystalline layer, with a hardness of 70 HRC. The tests of resistance to abrasive wear of the metal-mineral type, according to ASTM G 65-00, have shown that the best usable properties are characterized by a layer made of Fe-Cr-Nb-B alloy. The metal-mineral abrasion resistance of this material is 11 times higher than a typical HARDOX 400 abrasion-resistant sheet.

**Author Contributions:** Conceptualization, J.G. and A.C.; Methodology, M.A.; Validation, A.K., M.Z.; Formal ˙ Analysis, J.G. and A.C.; Investigation, M.A. and M.Z.; Writing-Original Draft Preparation, J.G.; Writing-Review & ˙ Editing, A.K.

**Funding:** The publication was co-financed from the statutory subsidy of the Faculty of Mechanical Engineering of the Silesian University of Technology in 2018.

**Conflicts of Interest:** The authors declare no conflicts of interest.
