The tribological properties of part surfaces, namely their wear resistance and friction properties, are decisive in many cases for their proper function. To improve surface properties, it is possible to create hard, wear-resistant coatings by thermal spray technologies. With these versatile coating preparation technologies, part lifetime, reliability, and safety can be improved. In this study, the tribological properties of the HVOF-sprayed coatings WC-17%Co, WC-10%Co4%Cr, WC-15% NiMoCrFeCo, Cr 3 C 2 -25%NiCr, (Ti,Mo)(C,N)-37%NiCo, NiCrSiB, and AISI 316L and the plasma-sprayed Cr 2 O 3 coating were compared with the properties of electrolytic hard chrome and surface-hardened steel. Four different wear behavior tests were performed; the abrasive wear performance of the coatings was assessed using a dry sand/ rubber wheel test according to ASTM G-65 and a wet slurry abrasion test according to ASTM G-75, the sliding wear behavior was evaluated by pin-on-disk testing according to ASTM G-99, and the erosion wear resistance was measured for three impact angles. In all tests, the HVOF-sprayed hardmetal coatings exhibited superior properties and can be recommended as a replacement for traditional surface treatments. Due to its tendency to exhibit brittle cracking, the plasma-sprayed ceramic coating Cr 2 O 3 can only be recommended for purely abrasive wear conditions. The tested HVOF-sprayed metallic coatings, NiCrSiB and AISI 316L, did not have sufficient wear resistance compared with that of traditional surface treatment and should not be used under more demanding conditions. Based on the obtained data, the application possibilities and limitations of the reported coatings were determined.

The present study is designed to find out if sesquiterpenes, α-humulene (HUM), valencene (VAL), β-caryphyllene-oxide (CAO) and trans-nerolidol (NER), are able to improve the antiproliferative effect of classical cytostatic drugs, 5-fluorouracil (FU) and oxaliplatin (1,2-diaminocyclohexaneoxalato-platinum, OxPt), in colon cancer cell lines Caco-2 and SW-620. In addition, the possible mechanisms of sesquiterpene action are studied. The results show significant ability of HUM and especially of CAO to enhance the anti-proliferative effects of FU and OxPt in cancer cell lines Caco-2 and SW-620. On the other hand, VAL and NER are ineffective. The action of CAO could be partly based on its ability to disrupt the mitochondrial membrane potential and to activate initiator caspases, but other mechanisms are probably also involved. Based on these results, CAO seems to have the potential for combination therapy of colon cancers and deserves further study.

The composition WC-(W,Cr) 2 C-Ni is one of the standard compositions used for the preparation of thermally sprayed coatings by high velocity oxy-fuel (HVOF) spraying. Surprisingly, this composition has been poorly investigated in the past. Frequent use of commercial designations WC-ÔCrCÕ-Ni, WC-Cr 3 C 2 -Ni, and WC-NiCr indicates the insufficient knowledge about the phase compositions of these powders and coatings. The properties of these coatings differ significantly from those of WC-Co and WC-CoCr coatings. In this paper, the results of different series of experiments conducted on HVOFsprayed WC-(W,Cr) 2 C-Ni coatings are compiled and their specific benefits pointed out. The focus of this study is on the analysis of the microstructures and phase compositions of the feedstock powders and coatings. Unlike WC-Co and Cr 3 C 2 -NiCr, WC-(W,Cr) 2 C-Ni is not a simple binary hard phase-binder metal composite. The phase (W,Cr) 2 C with unknown physical and mechanical properties appears as a second hard phase, which is inhomogeneously distributed in the feedstock powders and coatings. As examples of coating properties, the oxidation resistance and dry sliding wear properties are compared with those of WC-10%Co-4%Cr coatings.

Elastic-plastic properties, namely, hardness and YoungÕs modulus, of four HVOF-sprayed hardmetal coatings were measured by instrumented indentation using Oliver-Pharr method Nanoindenter XP MTS with a continuous stiffness measurement (CSM) module. The results show that with sufficient number of CSM measurements, one can distinguish between indents made in the hard particles and indents made in the binder material. This can be accomplished by analyzing the plots of hardness and YoungÕs modulus versus load (or versus indentation depth). Further development of the dependence curves enables the load (or indentation depth) to be set to correspond to the point of transition from a single structure component to the composite material and to determine the properties of both. Comparison of results of CSM measurement with the results of single indentation measurement at a defined load reveals a new perspective on the origin of the indentation size effect in hardmetal coatings. The measurements show that the increase in both the hardness and YoungÕs modulus with decreasing load is caused mainly by the predominant influence of hard particles in the coatings.

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