SU1482977A1 - Composition for diffusion chrome-plating of steel articles - Google Patents

Abstract

The invention relates to the chemical and heat treatment of metals and alloys and can be used in the engineering, instrument-making, chemical and other industries to increase the operational durability of machine parts and tooling. The aim of the invention is to increase the saturability of the composition, increase the corrosion resistance and microhardness of products. This is achieved by using a composition for diffusion chromium coating containing chromium oxide, powders of aluminum and copper, ammonium chloride, in the following ratio of components, wt.%: Copper powder 20-30, aluminum powder 15-17, ammonium chloride 2-3, chromium oxide the rest . 2 tab.

Description

The invention relates to the chemical and thermal treatment of metals and alloys, and can be used in engineering, instrument-making, chemical and other industries to increase the operational durability of machine parts and tooling.

The purpose of the invention is to increase the thickness of the diffusion layer, increasing its corrosion resistance and microhardness.

According to the proposed method, the composition for diffusion chromium plating of steel products includes chromium oxide, aluminum powder, copper powder, ammonium chloride in the following ratio, wt.%:

Copper powder 20-30

Aluminum powder 15-17

Ammonium Chloride 2-3 Chromium Oxide Else Copper powder, introduced in an amount of 20-30 wt.% In the composition for chromium plating, when aluminum restores chromium oxide, interacts with the reduced chromium to form an alloy.

When steel products are saturated from a powder mixture of the proposed composition, copper displaces chromium atoms from the alloy, thereby contributing to the formation of a defect-free diffusion layer, and increases the corrosion resistance, thickness, and microhardness of the layer.

In addition, the introduction of copper powder in an amount of 20-30 wt.% Ensures manufacturability of the chromium compound and the maximum chromium plating rate.

Ammonium chloride in the proposed composition is used as an activator.

Chromium oxide in the proposed composition - standard powder (GOST 2912- 73), copper powder - standard (GOST 4960-75), aluminum powder - standard (GOST 6058-73), activator - according to GOST 3773-72

To select the optimal amount of the copper powder to be added, mixtures are prepared from the components containing each, in wt.%: Aluminum 16, ammonium chloride 1.5 (as in the prototype), differing from each other in a copper content equal in each mixture, wt.% : 15; 20; 25; thirty; 35, as well as the chromium oxide content, constituting an additional part up to 100% in each mixture.

The process of diffusion saturation is carried out at 920-950 ° C for 4 hours in containers with a fusible valve.

Data on the effect of the amount of copper in the powder mixture on the thickness of the diffusion layer, microhardness, and corrosion resistance are presented in Table. 1 o

As follows from Table 1, a change in the content of copper powder from 20 to 30 has a significant effect on the thickness, microhardness, and corrosion resistance of the chrome coating.

The content of copper powder in the mixture of more than 30 wt.% After the saturation process leads to a sharp decrease in the density and thickness of the diffusion layer of the samples and a decrease in corrosion resistance to 5.2-10 - 6.1-10 g / mm-h and microhardness to 10300-12900 MPa, and the thickness of the layer is 18-29 microns

When the content of copper powder in the mixture is less than 20, a decrease in the thickness of the diffusion layer is observed, while the corrosion resistance drops to 2, -3, g / mm.h and the microhardness decreases to 11500-13400 MPa.

When the content of copper powder in the mixture is 20-30 wt.%, The diffusion layer has a sufficient thickness, corrosion resistance, microhardness.

Thus, the best indicators are given by compositions 2–4 (Table 1), including, in May.%:

Copper powder 20-30

Aluminum powder 15-17

Ammonium Chloride 1-2

Chromium Oxide Else

Next, the reconstituted mixture is sieved through a sieve and mixed with the activator in a cone mixer for 10-15 minutes.

The sealing of the container is carried out with boric anhydride with crushed glass, which form a fusible seal in the process of heating the container.

The saturation process is carried out at 930 ± 20 ° C for 4 hours.

Example 1. A mixture for saturation is prepared, containing, in% by weight:

Copper powder 20

Aluminum Powder 15

Ammonium Chloride 2

Chromium oxide 63

The mixture is pre-reduced in a container at 900 ° C. In this case, aluminum powder reduces chromium oxide to pure chromium. Reduced chromium reacts with copper to form a chemical compound. In addition, copper powder plays the role of an inert additive that lowers the final reduction temperature of chromium oxide. Cool the container to room temperature and use the mixture to saturate with the addition of 1% ammonium chloride.

The prepared samples of steel 45, U10 and HVG are packed in a container and filled with the prepared mixture. Direct the fusible plug and place the container in an oven heated to 930 ° C, incubated for 4 hours. Then the container is removed from the furnace, cooled to room temperature and unpacked.

The test results are presented in table.

Example 2. The process is carried out analogously to example 1, while the saturating composition has the following content of components, wt.%:

Copper powder 25

Aluminum Powder 16

Ammonium Chloride 2.5

Chromium oxide 56.5

The chromium plating process is carried out for 4 hours. The test results are presented in Table 2.

Testing of the obtained samples in examples 1 and 2 and prototype conducted 5114

in a 10% solution of nitric acid at a solution temperature of 70 ° C. The corrosion rate was estimated by the weight loss of the samples.

Weighing was carried out on the scales MONNA NIKIZAKTAPY PRECYUWET with an accuracy of up to 0.001 g.

Microhardness was determined on a PMT-3 microhardness meter, the thickness of the diffusion layer was measured on a Neophot-21 metallographic microscope, increasing the saturability of the sample, the comparative tests, and the increase in corrosion resistance are presented in Table 2. These products and microhardness, it was similarly used It will preserve the components in the following relevant compositions (examples 1 and 2 of table 2) allows to increase the corrosion resistance of 1.3-5 times, the thickness of the diffusion layer 1.7-2.8 times and microhardness 1.3-1, 4 times.

20

wearing, wt.%: Copper powder Aluminum powder Ammonium chloride Chromium oxide

20-30

15-17

2-3

The rest: t a -s l c «i

6

Claims (1)

In addition, lowering the saturation process temperature makes it possible to use standard electric furnaces. Invention Formula A composition for diffusing chromium plating of steel products, including chromium oxide, aluminum powder, copper powder, ammonium chloride, characterized in that wearing, wt.%: Copper powder Aluminum powder Ammonium chloride Chromium oxide 20-30 15-17 2-3 The rest: t a -s l c «i Editor M.Petrova Compiled by I. Petrov Tehred L. Serdyukova Proofreader S. Shekmar Order 2787/22 Circulation 941 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 6lit2 Subscription