Boriding abilities of boriding media based on boron carbide, amorphous boron and mixtures for a simultaneous saturation by boron, chromium and titanium have been compared. As an object of study boride coatings on carbon steels 45 and U8A have been chosen. Borating was done from powder mixtures in a chamber furnace of SNOL type. The microstructure and thickness of the diffusion coatings were studied on cross microsections by means of optical microscopy. The boride phases were identified by «color etching» and by X-ray diffraction. It is shown that during simultaneous saturation of carbon steels with boron, chromium and titanium the diffusion processes occur much more intensively. Addition of carbide-forming elements such as chromium and titanium into a boriding mixture results in a significant acceleration of boron diffusion in carbon steels 45 and U8A. During a simultaneous multicomponent saturation with boron, titanium and chromium the rate of diffusion layer formation on carbon steels is higher than under one-component boriding. In the case of a multicomponent saturation by boron along with strong carbide-forming elements (chromium and titanium), an increase of the carbon content of carbon steel under saturation from 0.45 to 0.8 wt.% has little effect on the formation of a diffusion layer. While in the case of one-component boriding the carbon content of the steel significantly affects both the thickness and microstructure of a boride coating, during a simultaneous saturation with boron, titanium and chromium the carbon content of the steel has practically no effect on the diffusion coating thickness. Проведено сравнение борирующей способности насыщающих сред для борирования на основе карбида бора и аморфного бора, а также смеси для одновременного насыщения бором, хромом и титаном. В качестве объекта из-учения были выбраны боридные покрытия на углеродистых сталях 45 и У8А. Борирование производили из порош-ковых смесей в камерной печи типа СНОЛ. Исследование микроструктуры и толщины диффузионных покрытий производили на поперечных микрошлифах при помощи оптической микроскопии. Идентификацию боридных фаз производили методом "цветного травления" и при помощи рентгеновской дифрактометрии. Показано, что при од-новременном насыщении бором, хромом и титаном углеродистых сталей, диффузионные процессы протекают значительно интенсивнее. Введение в состав борирующей смеси карбидообразующих элементов -хрома и тита-на способствует значительному ускорению процессов диффузии бора в углеродистых сталях 45 и У8А. При одно-временном многокомпонентном насыщении бором, хромом и титаном скорость образования диффузионного слоя на углеродистых сталях выше, чем при борировании. В случае многокомпонентного насыщения бором совместно с сильными карбидообразующими элементами (хром и титан) увеличение содержания углерода в насыщаемой уг-леродистой стали от 0,45 до 0,8 мас.% оказывает слабое влияние на процесс образования диффузионного слоя. Если при однокомпонентном борировании содержание углерода в стали значительно влияет как на толщину,...
Studies have been conducted on the effect of the degree of doping with chromium and nickel on the formation of boride coatings on steels AISI430 and AISI303. The saturation was carried out in a SNOL-type chamber furnace equipped with a PID controller from a powder saturating medium in an unsealed crucible. A mixture of boron carbide powders (70 wt. %), potassium tetraborate KBF4 (7 wt. %) and graphite – up to 100 % was used as a saturating medium. The process temperature was 900 ºC, the saturation time was 2.5 hours. Upon completion of the high-temperature exposure, the crucibles were removed from the furnace and cooled in air to the 50–60 ºC temperature. Diffusion coatings with a total thickness of 120 μm were formed on steel AISI430 and 75–85 μm on steel AISI303. The thickness of the boride layer for both steels was 45–50 µm.
In this paper we studied the microstructure of diffusional coatings based on boron and titanium, obtained from different pastes. Using energy-dispersive analysis, the elemental composition of the diffusion coatings was determined. The influence of the elemental composition and microstructure on the operational life of products, hardened in accordance with the proposed technology, in the conditions of abrasive wear in sulfuric acid solution was investigated.
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