RU2737796C1 - Compound composition for nitriding parts from alloyed steels - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to composition of thermosetting epoxide mixture for nitriding of parts from alloyed steels during chemical heat treatment. Said composition of thermosetting epoxide mixture is a compound consisting of nitrogen-containing epoxy resin (A), amine, or amide, or amino-amide curing agent (B) and filler in form of aluminium powder (B) in the ratio, pts. wt. A:B from 100:5 to 100:80 and (A + B):B from 100:80 to 100:400.

EFFECT: increased wear and high surface hardness of parts from alloyed steels.

1 cl, 5 ex

Description

The invention relates to the field of obtaining materials, in particular, to the composition of a thermosetting epoxy compound for coating a part in the implementation of chemical-thermal treatment of alloy steels operating under conditions of increased wear, where high surface hardness of parts is required.

The known method of nitriding (AS No. 945245 declared. 09/17/1980, publ. 07/23/1982, bul. No. 27) where before heating the parts are coated with a thickness of 3-30 microns As coatings used soot, chrome, copper or aluminum.

The disadvantages of this method are uneven and low surface hardening, as well as low labor productivity. The coatings are applied by electroplating or vacuum deposition. The method is reduced to processing parts in the chamber with ammonia for a long time (sometimes more than a day), which is ineffective, since hardening of steel surfaces with nitrogen occurs due to the formation of nitrides when exposed only to atomic nitrogen, which is released during the dissociation of ammonia in small amounts and accumulates for a long time.

The known composition of the powder mixture for slip coatings, containing silicon, zirconium boride with the preparation of slip on an organic binder (patent RU No. 2471751 dated 01/10/2013). However, this composition also does not allow its use in nitriding by applying slip coatings.

A known method of nitriding parts made of structural alloy steels, including heating the parts in a furnace to a temperature of 540-650 ° C, isothermal exposure at a heating temperature. Preliminarily, a nanosized copper film with a thickness of 150-200 nm is applied to the surface of the part, which ensures an increase to a given value of the thickness of the monolithic zone of cermet in the diffusion nitrided layer obtained on the surface of parts from structural alloy steels without increasing the duration of the nitriding process and without reducing its hardness (see RF patent No. 2614292, IPC S23S 28/04, publ. 2017).

The disadvantages of this method are the complexity of electroplating a nano-sized copper film (less than 500 nm) on parts made of stainless steels (high-alloyed), the use of toxic ammonia, and low labor productivity.

The closest to the claimed method in technical essence is adopted as a prototype (see RF patent No. 2692006, IPC C23C 8/26, publ. 2019). the method of cyclic gas nitriding of parts made of high-alloy steels includes heating in a furnace to a temperature of 540-650 ° C, isothermal holding at a heating temperature and subsequent cooling together with the furnace in an ammonia atmosphere. Preliminarily, a slip coating is applied to the surface of the parts by dipping, consisting of a powder of chromium oxide Cr ₂ O ₃ and a binder - a solution of celluloid in a mixture of acetone and acetic acid.

The disadvantages of this method are the use of toxic ammonia, low labor productivity.

The aim of the claimed invention is to develop a thermosetting epoxy compound composition for a safe and effective process of nitriding products made of alloy steels operating under conditions of increased wear, where high surface hardness of products is required, by creating a surface layer containing metal nitrides using standard factory equipment and commercially available industrial equipment. materials - aluminum powder, nitrogen-containing epoxy resins and hardeners.

This goal is achieved by the fact that the composition of the thermosetting epoxy compound consists of a nitrogen-containing epoxy resin (A), an amine or amide or amine-amide hardener (B) and a filler - aluminum powder (C) - in a ratio (parts by weight) A: B 100: 5 to 100: 80 and (A + B): C 100: 80 to 100: 400.

The proposed composition has strong adhesion to steels and is applied to the degreased steel part with a brush and / or one-, two-nozzle spray gun. Depending on the type of epoxy resin and hardener, the applied composition is cured in an oven (at a temperature of 30 ° C to 160 ° C) in a short period of time (from 3 to 180 minutes), turning into a hard high-strength coating. After that, the steel part with the cured coating is subjected to heat treatment at temperatures from 500 ° C to 1000 ° C for 20 to 80 minutes), as a result of which the coating rapidly degrades, forming atomic nitrogen with an admixture of atomic carbon in the aluminum melt medium, which is a catalyst formation of metal nitrides. As a result of this process, aluminum nitride is formed at a temperature of 600 ÷ 800 ° C (without a catalyst - at a temperature of 1000 ° C) having a microhardness of 12 GPa and a melting point of 2000 ° C, inferior in these parameters to nitrides of other metals, but significantly superior to alloyed steels. Then the cooled part is treated with a hydrochloric acid solution to remove unreacted aluminum.

Example 1

A liquid epoxyaniline resin (A) of EA grade (TU 2225-606-11131395-2003) containing 34% of epoxy groups is loaded into a reactor with a high-speed stirrer, in an amount of 100 wt. hours, and then add 40 wt. including hardener (B) - para-aminobenzylamine (pilot industrial product) and 240 wt. including aluminum powder (B). The mixture is stirred at 30 ° C for 5 min, and then the resulting compound is unloaded into an intermediate container, from which it is applied to a steel part with a brush or spray gun, kept at ambient temperature for 60 min until the viscosity increases and heat treated at 90 ° C for within 90 minutes. The resulting coating is resistant to accidental impacts (specific toughness of at least 25 kJ / ^m2, compressive strength of 200 MPa). Next, the coated part is placed in a crucible furnace and heat treated at 750 ° C for 30 minutes. At this time, there is a complete destruction of the epoxy compound with the release of atomic carbon and nitrogen, which is actively absorbed by molten aluminum with the formation of aluminum nitride on the surface of the steel part. At the same time, side reactions of the formation of nitrides and carbides of alloying metals occur on the surface due to the reaction of the latter with active atomic nitrogen and carbon, which also contribute to an increase in the surface hardness of the steel product. The cooled part is treated with 20% hydrochloric acid to remove traces of unreacted aluminum.

Examples 2 ÷ 5 are carried out analogously to example 1 with changing individual parameters.

Example 2

Carried out analogously to example 1, but as an amine-containing epoxy resin (A) used resin UP-610 (triglycidyl paraaminophenol, TU 2225-606-11131395-2003) with a liquid eutectic mixture MFDA (meta-phenylenediamine, GOST 5826-78) with 4.4 '-DADFM (4,4'-diaminodiphenylmethane, CAS 101-77-9) (B) in the ratio A: B = 100: 80.

Example 3

Carried out analogously to example 1, but as an epoxy resin, triglycidyl isocyanurate of the ETSN brand (TU 6-05-1190-76) is used, and 2-methylimidazole (CAS 693-98-1) is used as a hardener in the ratio A: B = 100: 5 with the ratio (A + B): B (aluminum powder) = 100: 160.

Example 4

Carried out analogously to example 1 using resin EA, but as a hardener used aminoalkylimidazole brand I-5-M (TU 6-21-11-03-113-93) in the ratio A: B = 100: 80, (A + B) : B = 100: 400 and a heat treatment temperature of 500 ° C for 60 minutes.

Example 5

Carried out analogously to example 1, but as a nitrogen-containing epoxy resin used tetraglycidil 3,3'-dichloro-4,4'-diaminodiphenylmethane EKhD (TU 2225-512-00203521-98) (A) and hardener I-5-M (TU 6-21-11-03-113-93) (B) in the ratio A: B = 100: 80, cured at 36 ° C for 80 minutes, and heat treated at 1000 ° C for 20 minutes.

Claims (1)

The composition of a thermosetting epoxy mixture for nitriding parts made of alloy steels, characterized in that it is a compound consisting of a nitrogen-containing epoxy resin (A), an amine, or amide, or amino-amide hardener (B) and a filler in the form of aluminum powder (C ), in the ratio, wt.h. A: B from 100: 5 to 100: 80 and (A + B): C from 100: 80 to 100: 400.