Features and regularities in formation of diffusion nickel-copper coatings on steels in the medium of low-melting liquid-metal solutions

Abstract

The paper considers the features and regularities of formation of Ni-Cu based diffusion coatings on the surface of steel products obtained as a result of diffusion metallization from the medium of low-melting liquid metal solutions. It was found out that a solid solution of Ni, Cu, Fe was formed in the main layer of coatings after applying the Ni-Cu coating on armco-iron, steel 20 and tool steel Kh12MF; it was characterized by approximately equal concentration of nickel and copper on the coating surface, it made 55 % Ni and 27 % Cu. As soon as the depth of the base layer increases, concentration of Ni and Cu in it gradually decreases, while the iron content also increases. During formation of Ni-Cu coatings on alloyed steels, selective diffusion of steel alloying elements deep into the coating is observed. It is established that the coatings have two layers -the main and the transition ones. At the same time, the maximal coating thickness constitutes 55 μm at the saturation temperature of 1150 °C and 6 hours duration. It was revealed that the main layer consists of Ni, Cu, Fe solid solution, also contains steel alloying elements and consists of columnar grains elongated in the direction of diffusion of the coating elements, as well as in its surface layer with thickness of about 5 μm. The layer of nano-scale grains with a cross-section size of 80-100 nm is forming. During formation of Ni-Cu based coatings, the phenomenon of displacement of the coating carbon and the steel alloying elements into the transition layer is confirmed; these carbon and steel elements do not interact with the coating elements.

Influence of diffusion alloying of structural steels by nickel and copper in the medium of low-melting liquid-metal solutions on their corrosion resistance

“…In addition to this structural aspect, the influence of elementary composition of coating on corrosion resistance should be underlined. It was found out in the previously conducted researches, that during DALLS the coating contains from solid solution Fe-Ni-Cu [12]. Presence of alloying elements in steel, e.g.…”

“…DALLS was conducted in the developed and patented unit for diffusion metallization in the medium of low-melting liquid-metal solutions, which allows to combine DALLS processes and consequent heat treatment [15].…”

“…The following TCT methods are used: cementation, nitriding, boriding, aluminizing, galvanizing etc. [9][10][11][12]. However, at present time use of these technologies is restricted, except of cementation and nitriding.…”

Влияние Комплексной Химико-Термической Обработки На Коррозионную Стойкость Стальных Изделий

“…https://elibrary.ru/CUJOGE. _________________________________________________________________________________ ВВЕДЕНИЕ Одной из наиболее актуальных проблем для современного машиностроения является улучшение характеристик стальных изделий методами поверхностного упрочнения [1][2][3]. В связи с этим, разработано достаточно большое количество технологий, обеспечивающих повышение износостойкости, коррозионной стойкости, прочности, пластичности и других характеристик изделий с помощью нанесения покрытий [4][5][6].…”

“…При этом технологии ХТО можно разделить на две группы: 1) технологии, которые оказывают основное влияние на поверхностный слой изделия (например, азотирование), не позволяя получать диффузионные слои большой толщины; 2) технологии, позволяющие повысить одну характеристику, при этом, снижая другую (например, при цементации увеличивается твердость, но снижается коррозионная стойкость). Одной из перспектив-ных технологий ХТО является комплексная ХТО (КХТО), заключающаяся в совмещении цементации и диффузионного легирования в среде легкоплавких жидкометаллических растворов (ДЛЛЖР) [3,4,[9][10][11]. Технология ДЛЛЖР основана на явлении изотермического, селективного переноса элементов покрытия, растворенных в легкоплавком расплаве, на поверхность изделия с последующим диффузионным взаимодействием элементов покрытия с основным материалом изделия [4].…”