Improving the tribological characteristics of the wear-resistant electrolytic coating of chromium and iron
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Tehnologie chimică. Industrii chimice și înrudite (1502)
Metalurgie (103)
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KORNEYCHUK , N.. Improving the tribological characteristics of the wear-resistant electrolytic coating of chromium and iron. In: Materials Science and Condensed Matter Physics, Ed. 9, 25-28 septembrie 2018, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2018, Ediția 9, p. 283.
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Materials Science and Condensed Matter Physics
Ediția 9, 2018
Conferința "International Conference on Materials Science and Condensed Matter Physics"
9, Chișinău, Moldova, 25-28 septembrie 2018

Improving the tribological characteristics of the wear-resistant electrolytic coating of chromium and iron

CZU: 66+669

Pag. 283-283

Korneychuk N.
 
State Agrarian University of Moldova
 
 
Disponibil în IBN: 12 februarie 2019


Rezumat

Despite the variety of methods providing energy costs reduction to overcome frictional forces in nodes of machines and equipment the significant place is occupied by wear-resistant galvanic coatings of chromium, iron, alloys and compositions based on them. Despite high anti-friction properties, they have low wettability and low oil absorption, especially for electrolytic chromium. Porous chrome plating and ironing is widely used in practice and achieving by mechanical, chemical or electrochemical methods. In machinery industry and repair production the greatest application has been obtained by chemical and electrochemical methods of cracked coatings dissolution what is happening by micro cracks to a depth of up to 60 μm with a coating thickness of 180-200 μm. At the same time, the wettability, oil absorption and coatings wear resistance are increased, especially in case of boundary friction. The accumulated practical experience allows stating that in some cases during the engine running process the intensive wear of practically the entire porous coatings layer occurs. However, as the depth of the pores increases, this leads to chromium mechanical strength decrease. In this case, it becomes necessary to form such coatings, the porosity of which across the entire cross-section has to be distributed evenly. Our studies have found that such coatings can be formed if the periodic mechanical activation of covered surface to be performed during the electrolysis. Studies found that changing value of cathode current density, electrolyte temperature, activating tool pressure, activation frequency, both amorphous and textured coatings of iron and chromium with different spatial orientation and the size of micro cracks are formed. At the same time, the oil absorption of chromium coatings precipitated by galvanomechanical method is 1.2 ... 1.5 times higher, and the wetting contact angle is 1.27 ... 1.66 times less than for similar precipitates in stationary conditions. Studies have revealed a correlation between structure, oil absorption, wettability and wear resistance of coatings. Thus, the wear resistance of chromium precipitated by the galvanomechanical method is 1.3 ... 1.8 times higher, and the friction coefficient is 1.5 ... 2 times less than in the coatings precipitated in stationary conditions. Studies of electrolytic iron coatings precipitated in stationary and galvanomechanical conditions allowed revealing that mechanical activation, as well as in chromating, ensures the formation of coatings in which the oil absorption and wettability is higher and depends on the electrolysis regimes and mechanical activation conditions. Thus, when the cathode current density increases from 100 to 500 A / dm2, oil absorption increases by 31%, wettability - by 2 times. Change in the grain size of activating tool from 40 to 100 μm promotes an increase in the oil absorption by two times to 35 mg / cm3, and wettability by 60%. The pressure of activating tool from 90 to 167 kPa exerts a similar effect on oil absorption and wettability. At the same time, all this contributes to the reduction of friction coefficient and increase in coatings wear resistance in 1.3 ... 2.2 times in comparison with coatings deposited under stationary conditions of electrolysis. Thus, the conducted studies confirm the possibility of increasing the tribological characteristics of iron and chromium electrolytic coatings deposited by galvanomechanical method.