SU981448A1 - Medium for glow-discharge nitriding - Google Patents

Description

The invention relates to the chemical heat treatment of metals and alloys, and more specifically to the nitriding in the glow discharge of machine parts and mechanisms.

. Various nitriding media are known in the glow discharge of C, containing 100% ammonia, or 10% ammonia + 90% argon, or 90% ammonia + 10% propane t.

However, the known compositions are characterized by a low corrosion resistance of the parts after nitriding.

Closest to the proposed technical essence and the achieved result is a glowing nitriding medium containing dissociated ammonia and 0.5-2% methane 2.

This medium makes it possible to increase the corrosion resistance of the products after nitriding in comparison with the above.

The purpose of the invention is to further increase the corrosion resistance of parts.

The goal is achieved by the fact that the composition for nitriding in the glow discharge, containing dissociated ammonia and a carbon-containing compound,

as carbon-containing compound contains carbon dioxide in the following ratio of components, wt.%:

Carbon dioxide 5-10

Dissociated

ammoniaEmost

Added to completely dissociated ammonia, consisting of 1 hour of nitrogen and 3 parts of hydrogen, carbon dioxide gas, when nitrated, decomposes in the cathode space. At the same time, the latter additionally contains ions of oxygen and carbon, which interact with the sprayed iron, form chemical compounds, these compounds, in turn, are deposited on the parts and decompose under the action of ionic

20 bombing. The decomposition of these compounds produces oxygen and carbon, which are adsorbed to the metal surface. All this leads to the fact that a zone of chemical compounds based on oxycarbonitride (Fe, Me) (N, C, 0) is formed on the surface of the parts, where Me is the alloying element. Dissolving some amount. oxygen in carbonitride increases

30 is the corrosion resistance of the latter, p. Gprtetelieipip (since the coating obtained is non-porous and uniformly covers the entire product) and the part itself. It should be noted that the content of carbon dioxide in the mixture of less than 5% does not lead to an increase in corrosion resistance, apparently due to the fact that little oxygen dissolves in the carbonitride, and when the content of carbon dioxide in the mixture is greater than 10%, the corrosion is reduced. durability and presentation of products (due to the appearance of multi-colored spots on them), perhaps this is due to too much oxygen saturation potential, which leads to surface oxidation and the appearance of pores in the chemical compound zone. The use of a dissociated ampliac in a mixture with 5-10% carbon dioxide provides an increase in corrosion resistance and a reduction in the fire risk of the nitriding process. Vol. This is as follows. Carbon dioxide is fire- and explosion-proof; moreover, it is a substance that registers combustion. The method is carried out as follows. In the receiver chamber of the installation for nitriding in the glow discharge, disc samples of steel 38XNMMPA were processed. Cathode cleaning and heating of the samples until they are carried out in a completely dissociated ammonia medium; exposure at this temperature to form a layer of a given depth is carried out in a mixture of completely dissociated ammonia with 5% carbon dioxide. Similarly, samples are processed in a mixture with 7.10 and 15% carbon dioxide, as well as in a completely dissociated aNBiwaKa medium (i.e., without carbon dioxide). For comparison, the samples were processed according to the method, taken as a prototype and with furnace nitriding according to the mode: holding at 520 ° C for 12 hours, holding at 540 ° C for 22 hours. After nitriding, 3 samples from each processing mode are subjected to corrosion tests: electrochemical dissolution at room temperature in a 3% solution of potassium chloride in water for 15 minutes. At the same time, potentiodynamic anodic polarization curves are taken from the surface of the samples using a P-5848 potentiostat, which allows determining the potentiation of pitting. After soaking in the electrolyte, the surface of the samples is examined at a magnification of 10 in order to determine the number of pitts in the area L / 25 mm. The results of electrochemical studies are shown in the table.

100 dissociated ammonia

95 dissociated ammonia + 5 carbon dioxide

93 dissociated ammonia + 7 carbon dioxide

90 dissociated ammonia + 10 carbon dioxide

85 dissociated ammonia + 15 carbon dioxide

90 ammonia + 10 propane

99 dissociated ammonia + 1 methane / prototype / 1140

20-30 small pits

No corrosion damage detected

No corrosion damage detected

No corrosion damage detected

20-30 small pits

Single (1 pc.) Pitting

Claims (2)

Single (1-3 pcs.) Pitings As can be seen from the table, when the content of carbon dioxide in the mixture is from 5 to 10%, the corrosion resistance, i.e. resistance to pitting, samples nitrided in the glow discharge are best. compared with pr4 radiated after processing by a known method. Glitter nitriding medium containing dissociated ammonia and carbon-containing compounds, which in order to increase corrosion resistance, it contains carbon dioxide in the following ratio of components, wt.%: Carbon dioxide 5 -15 Dissociated ammoniaCost € 1kl Sources of information taken into account during the examination 1. Adjustable nitrogen and nitrogen processes. M., NIIiniformt Zhmash, 1976, 13-76-20, p. 14-19. 2. USSR author's certificate according to the application 3253031 / 22-02, cl. C 23 C 11/14, 1981.