New method of increase of corrosion resistance of steels
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PARSHUTIN, Vladimir; PARAMONOV, Anatolii; KOVALI, Alexandr; CHERNYSHEVA, Natalia; SHOLTOYAN, Nicolai. New method of increase of corrosion resistance of steels. In: Materials Science and Condensed Matter Physics. Editia a 8-a, 12-16 septembrie 2016, Chişinău. Chişinău: Institutul de Fizică Aplicată, 2016, p. 316. ISBN 978-9975-9787-1-2.
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Materials Science and Condensed Matter Physics
Editia a 8-a, 2016
Conferința "International Conference on Materials Science and Condensed Matter Physics"
8-th Edition, Chişinău, Moldova, 12-16 septembrie 2016

New method of increase of corrosion resistance of steels


Pag. 316-316

Parshutin Vladimir, Paramonov Anatolii, Kovali Alexandr, Chernysheva Natalia, Sholtoyan Nicolai
 
Institute of Applied Physics, Academy of Sciences of Moldova
 
Disponibil în IBN: 6 august 2019


Rezumat

In mechanical engineering and instrument making for increase of corrosion resistance of details of machines, the tool and industrial equipment use the different combined processing methods.   It is known that process of an electric spark alloying, allows to receive working surfaces with high physicomechanical properties. However they have small corrosion resistance because of high porosity and crack formation of the put covering because of what metal of a substrate can etching. Carrying out chemicothermal treatment of the alloyed layer does not influence continuity of a covering. After it in pores is forming only the nitride layer which corrosion resistance can be insufficient in a number of aggressive environments that leads to underetching of a covering, its fall and, thereby, failure of all detail forms.   Researches showed that there is an opportunity to increase corrosion resistance of the steels subjected to an electric spark alloying and to provide necessary corrosion resistance of metal in pores.   It is possible at the following method: apply with previously electric spark alloying corrosion and wearproof metal on a detail surface. The alloying is carried out layer-by-layer with length of impulses from 10 to 2500 microsec, with a frequency of 1500-25 Hz respectively. At the first stage - processing was conducted on the soft mode - duration of impulses of 30 microsec and the frequency of 1200-1500 Hz. As a result received a covering 0.1-0,15 mm thick from a small roughness and small number of pores. At the second stage worked at the rough mode - duration of impulses of 1000 microsec and the frequency of 50-100 Hz. At the same time the covering 0.15-0.2 mm thick was put. At the third stage processing was again conducted on the soft mode - duration of impulses of 30-40 microsec and the frequency of 1200-1500 Hz. Put a covering 0.1-0.2 mm thick. The layer-by-layer alloying allows receiving tight, homogeneous coats with a small roughness.   Then the detail is processing to chemicothermal treatment within 1-5 minutes in the electrolyte containing inorganic nitrogenous compounds with an additive of 0.5-15 g/l of the tannin at an electrode voltage of 150-220V, current density 1-20A/cm2 and temperature of the anode 600-900 0С with the subsequent oxidation in electrolyte.   After that the detail is kept within 0.5-10 hours in solution of the concentrated orthophosphoric acid and/or sodium nitrite solution concentration of 30-150 g/l. Then the detail is washed, dried up and electrolytic fill covering pores with insulating material.   In this case currents of anodic dissolution in comparison with a steel surface decrease by 120-280 times, in comparison with only the alloyed surface - in 10,7-12,1 times, and in comparison with the alloyed surface and the subjected chemicothermal treatment and passivation in orthophosphoric acid - by 2,7-3,0 times.   As a result of the processing, which is carried out thus, corrosion resistance of details, thanks to substrate metal passivation in pores and to creation of a layer of nitrides in them and tannates is promoted. It allows avoiding underetching of the corrosion and anti-wear coating put with an electric spark alloying and its fall.