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Ductile cast irons are materials with good ductility and toughness, but they are susceptible to high wear rates since they have low hardness. One way to increase their wear resistance is through thermo-reactive diffusion treatments (TRD), in which carbide layers are produced on the surface of the material. In this study, two ductile cast irons (with and without the addition of copper) were treated in a salt bath composed of borax, ferroniobium (16 wt.%) and aluminum (3 wt.%) at 1000°C for 4 h. The XRD and micro-hardness analysis indicated that NbC layers were produced with hardness values higher than 2000 HV. Two methods were used to examine the adherence of the layer to the substrate. In the first method, indentations were performed using Rockwell C scale (VDI 3198). The second method used Vickers micro-hardness indentations (loads 100, 200, and 300 gf) at the interface layer/substrate. In both tests, the layers showed good adhesion to substrates. The 3198 VDI test also showed that the NbC layer produced good toughness. The results of micro-adhesive and micro-abrasive wear tests showed that the layer was very effective in increasing wear resistance.

Austenitic stainless steels form the largest family of alloys in terms of number and applications. They are characterized by having good toughness, weldability, cold formability, and corrosion resistance in various situations. However, because they cannot harden by heat treatment, they exhibit low wear resistance. Suitable coatings can increase their wear resistance and expand their usability range. Boride coatings, with their high hardness and wear resistance are a good candidate for this purpose. In this work, samples of stainless steels, AISI 304 and UNS S31254, were subjected to liquid boriding at 950°C for 2 and 4 h. Optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Vickers hardness tests were performed, along with tests for micro-adhesive wear (fixed-ball type). The boriding treatment resulted in the formation of layers with high hardness, in the range of 1800 to 2000 HV, which is typical for boride layers. Micro-adhesive wear tests demonstrated the great increase in wear resistance obtained through this treatment.