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The influence of titanium diboride additives on microstructure and wear resistance of NiCrBSi thermally sprayed coatings deposited on a steel substrate has been studied. NiCrBSi-based composite powders with 10, 20, 40 wt.% TiB2 particles content were produced. The structure of NiCrSiB-TiB2 coatings consists of TiB2 and CrB grains distributed in Nibased matrix. The wear resistance of NiCrSiB-TiB2 plasma sprayed coatings in dry sliding conditions against the same coating using pin-on-disk tester. It was determined that the amount of titanium diboride particles in NiCrBSi-based coatings influences essentially on the wear resistance and wear mechanism. The NiCrBSi-based plasma sprayed coatings containing 20 wt.% of TiB2 possess the high wear resistance due to the realization of mechanical-oxidation wear mechanism.

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In this study the influence of the TiB2, ZrB2, and CrB2 additives into NiAl-intermetallics on their wear behavior under friction conditions at the high temperature in the pair with steel has been investigated. It was shown, that the borides additives have influenced on the wear mechanism, significantly increasing the wear resistance of composite coatings pointed out. Among the coatings studied the NiAl-15 wt. % CrB2 coating showed the best result.

The main goal of this work is to study dry sliding wear behavior of NiCrSiB-TiB2plasma sprayed coating against NiCrSiB coating. NiCrSiB-based powders with 10, 20, 40 wt.% TiB2particles content were deposited on steel substrates by plasma spraying. The structure of NiCrSiB-TiB2coatings consists of Ni-based matrix and TiB2and CrB grains. Among the coatings studied, the NiCrSiB-20wt.%TiB2shows excellent wear-resistance. The worn surfaces were observed using scanning electron microscopy and Auger electron spectroscopy to determine the wear mechanisms.

The development of composite materials (CM) in the systems "metal-refractory compound" is one of the up-to-date trends in design of novel materials aimed at operating under the conditions of significant loads at high temperature. To design such material, NiAl, which is widely used for deposition of protective coatings on parts of gas-turbine engines, was selected for a matrix. To strengthen a NiAl under the conditions of intense wear and a broad temperature range (up to 1000 °C), it is reasonable to add refractory inclusions. Introduction of refractory borides into matrix leads to a marked increase in metal wear resistance. In order to research the behavior of the designed composites at high temperatures and to study the influence of oxides on the friction processes, the authors carried out high temperature oxidation of CM of the above systems at 1000 °С for 90 min. It was determined that all of the composites were oxidized selectively and that the thickness of oxide layers formed on the boride inclusions is 3-7 times that on the oxides formed on the NiAl matrix. The mechanism of wear of gas-thermal coatings of the NiAl-МеB2 systems was studied for conditions of high temperature tribotests using the «pin-on-disc» technique. The obtained results indicate that introduction of TiB2, CrB2 and ZrB2 leads to their more intense oxidation during high temperature tribotests as compared to the matrix. The oxides formed on refractory borides act as solid lubricants, which promote a decrease in wear of the contact friction pairs. For more detailed investigation of the effect of tribo-oxidation products on the friction processes, tribotests were conducted for prior oxidized (at 900 °С) coatings NiAl-15 wt.% CrB2 (TiB2, ZrB2).

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