Wetting and interfacial behavior of Fe-based self-fluxing alloy-refractory compound systems

In this study the wettability and interfacial behaviour of the TiC–FeNiCrBSiC and TiB₂–FeNiCrBSiC systems were investigated. The wetting experiments were performed by the sessile drop method at 1150 °C under a vacuum. The contact angles of TiC and TiB₂ wetting by melted Fe-based self-fluxing alloy were 51° and 36°, respectively. Thermodynamic calculations were carried out to understand the metal-ceramic interaction mechanism in the TiC–FeNiCrBSiC and TiB₂–FeNiCrBSiC systems. The structure of the interface region in the TiB₂–FeNiCrBSiC system was characterized by the optical microscopy and SEM-EDS analysis. The formation of Fe, Ni, Cr and Mo complex borides was revealed within the interface region of the TiB₂–FeNiCrBSiC system.Досліджено змочування та контактну взаємодію в системах TiC–FeNiCrBSiC і TiB₂–FeNiCrBSiC. Кінетику змочування вивчено методом “лежачої краплі” в вакуумі при температурі 1150 °C. Кути змочування TiC і TiB₂ самофлюсівним сплавом на основі заліза становили 51° і 36° відповідно. Для виявлення особливостей контактної взаємодії на межі металевий сплав–кераміка проведено термодинамічні розрахунки систем TiC–FeNiCrBSiC і TiB₂–FeNiCrBSiC. Методами оптичної та скануючої електронної мікроскопії вивчено структуру зони взаємодії в системі TiB₂–FeNiCrBSiC. Виявлено формування складних боридів Fe, Ni, Cr і Mo в зоні взаємодії системи TiB₂–FeNiCrBSiC.Исследовали смачивание и контактное взаимодействие в системах TiC–FeNiCrBSiC и TiB₂–FeNiCrBSiC. Кинетику смачивания изучали методом “лежащей капли” в вакууме при температуре 1150 °C. Углы смачивания TiC и TiB₂ самофлюсующимся сплавом на основе никеля составляли 51° и 36° соответственно. Для выявления особенностей контактного взаимодействия на границе металлический сплав–керамика были проведены термодинамические расчеты систем TiC–FeNiCrBSiC и TiB₂–FeNiCrBSiC. Методами оптической и электронной микроскопии изучали структуру зоны взаимодействия в системе TiB₂–FeNiCrBSiC. Установлено формирование сложных боридов Fe, Ni, Cr и Mo в зоне взаимодействия системы TiB₂–FeNiCrBSiC

High Temperature Sliding Wear of NiAl-based Coatings Reinforced by Borides

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)

ВЛИЯНИЕ СОСТАВА МАТЕРИАЛОВ НА МЕХАНИЗМ ИХ ВЫСОКОТЕМПЕРАТУРНОГО ГАЗОАБРАЗИВНОГО ИЗНАШИВАНИЯ

The influence of the material composition on their wear mechanism and intensity at hightemperatare gas-abrasive tests were studied. The macro- and microstractares of materials surfaces after testing in a two-phase high-velocity flow of SiC abrasive particles at T = 500 °N were studied. It is shown that for the nickel alloy subjected to temperature and high-velocity flow of abrasive particles, intensive deformation of the sample takes place with the formation of a wavy relief on its surface. For the developed composite materials of the NiAl-CrBj system, deformation of the surface is difficult by the presence of a strengthening boride phase. The highest values of wear resistance correspond to the developed NiAl-15% CrBj compositematerialИсследовано влияние состава материалов на механизм и интенсивность их изнашивания при высокотемпературных газоабразивных испытаниях. Изучены макро- и микроструктуры поверхностей материалов после испытаний в двухфазном высокоскоростном потоке абразивных частиц карбида кремния при Т = 500 "С. Показано, что для сплава ЖС 26 при испытаниях под воздействием температуры и высокоскоростного потока абразивных частиц происходит интенсивное деформирование образца с формированием на его поверхности волнообразного рельефа. Для разработанных композиционных материалов системы NiAl-CrB2 деформация поверхности затруднена из-за наличия упрочняющей боридной фазы. При этом наиболее высокие значения износостойкости соответствуют композиту NiAl -15% CrВ

ИССЛЕДОВАНИЕ МЕХАНИЗМОВ ИЗНАШИВАНИЯ ОКСИДОВ ТИТАНА, ХРОМА И ЦИРКОНИЯ ПРИ ТРЕНИИ В УСЛОВИЯХ ВЫСОКИХ ТЕМПЕРАТУР

Results of high temperature friction tests of Cr2O3, TiO2, ZrO2 gas-thermal oxide coatings was presented in this work. Coatings was obtained by plasma spraying method. Tribotechnical properties of oxides was investigated by «pin-on-disc» scheme under T = 500 °C. These investigations showed that chromium oxide possess the highest wear resistance due to formation of complex (NiCrAl)xOy oxide film on Cr2O3 surface during friction process, that prevent immediate contact of coating and counter-body and decrease wear in this friction couple.В статье представлены результаты испытаний газотермических покрытий из оксидов Cr2O3, TiO2, ZrO2 в условиях высокотемпературного трения. Покрытия из оксидов наносились методом плазменного напыления. Триботехнические свойства оксидов исследовались по схеме «pin-on-disk» при Т = 500 °С. Данные исследования показали, что оксид хрома обладает наибольшей износостойкостью благодаря формированию в процессе трения на его поверхности сложного оксидного слоя (NiCrAl)хOу который предотвращает непосредственный контакт покрытия с контр-телом и уменьшает износ в данной паре трения

Hydroabrasive resistance of composite gas-thermal coatings based on intermetallic compounds

The resistance of gas-thermal coatings based on intermetallic compounds and steels under hydroabrasive wear conditions is determined. Recommended composite coating Ni-Ti – 30% Cr-B2 to improve the reliability of machine parts that work in conditions of aggressive exposure to abrasive in aqueous media

Effect of TiB₂ Additives on Wear Behavior of NiCrBSi-Based Plasma-Sprayed Coatings

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 Ni-based 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