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Solid boriding thermochemical treatment was carried out on AISI H13 steel. Two boriding agents were used: Ekabor 1-V2 commercial powder and a mixture of 73?26 wt-% borax, 24?06 wt-%SiC, 1?22 wt-%NH 4 Cl and 1?46 wt-%NaCl. Pin on disc wear tests were carried out to investigate tribological behaviour. After the wear tests, samples were cut in cross-section to evaluate the thickness and morphology of the boride layer by scanning electron microscopy (SEM) and Vickers microhardness. Wear mechanisms were evaluated by SEM. A large improvement in wear resistance was observed for borided samples compared with samples that had been quenched and tempered. The thickness of the borided layer was higher for samples borided with Ekabor powder than those borided with the mixture. In comparison with quenched and tempered samples, borided samples had a higher incidence of cracks, which favours spalling and reduction of grooves formed by abrasive wear.

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In this study, the thermal, dynamic-mechanical and tribological behavior of nanocomposites of a photocurable epoxy-acrylate resin and multiwalled carbon nanotubes (MWCNT) are investigated. A route consisting of a combination of sonication, mechanical and magnetic stirring is used to disperse 0.25-0.75 wt. (%) MWCNT into the resin. Two photocuring cycles using 12 hours and 24 hours of UV-A radiation are studied. The storage modulus, the loss modulus and the tan delta are obtained by dynamic mechanical analysis. Thermal stability is investigated by thermogravimetry, morphology by transmission electronic microscopy (TEM) and tribological performance using a pin-on-disk apparatus. The results indicate an increase in stiffness and higher ability to dissipate energy, as well as a shift in the glass transition temperature for the nanocomposites. The addition of nanofillers also decreased friction coefficient and wear rate of the nanocomposites but did not change the observed wear mechanisms

The replacement of electrolytic hard chrome (EHC) by high velocity oxy-fuel (HVOF) sprayed coatings is investigated due to the toxicity of EHC process. The wear behavior of AISI 4140 steel coated by HVOF-, EHC-process was compared to quenched and tempered (Q&T) steel using a pin-on-disc apparatus. The wear tests were conducted at room temperature, 10 N applied load and 0.1 m/s sliding speed in dry condition. The results were interpreted on the basis of the microstructure and hardness. Wear micromechanisms were investigated by SEM. The predominant presence of the WC phase and the formation of W 2 C and W 3 C phases, associated with decarburization of superheated regions of the CoCr binding phase of HVOF-coated samples were observed by X-ray diffraction analysis. Wear tests results show that the WC-10Co-4Cr coating exhibits better wear resistance than the EHC coating and Q&T steel. The formation of a wear resistant tribolayer was determinant to the excellent wear behavior of the thermally sprayed coating.

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