CS252316B1 - Etching agent for microstructure development - Google Patents

Abstract

The solution concerns an etchant for developing the micro and macrostructure of ferrous and non-ferrous alloys. When evaluating the microstructure of, for example, eutectic crystallization of gray cast irons, it is necessary to wash off the adhering layer of copper on the metallographic sample with an aqueous solution of ammonia with existing etchant, which is both harmful to health and also significantly prolongs the time required to produce a metallographic section. Etch according to the solution based on hydrochloric acid, nitric acid and water, characterized in that it consists of: 0.5 to 3.0 parts of pure magnesium chloride, 1.0 to 10.0 parts of pure aluminum chloride, 3.0 to 15.0 parts of pure cupric chloride, 3.0 to 9.0 parts of pure copper sulfate, 5.5 to 16.5 parts of 37% hydrochloric acid, 2.7 to 13.5 parts of 65% nitric acid, 100 parts of distilled water, the said parts being parts by weight. The etchant prevents the precipitation of copper deposits on the surface of the manufactured and etched metallographic section, thereby improving its processing and accelerating the possibility of evaluation. This makes etching "on segregation" very advantageous.

Description

The invention relates to inducing a microstructure of ferrous and non-ferrous metals value macrostructure and microstructure for metallographic analysis.

The prior art method for inducing both macro and microstructure alloys is that the polished sample is etched with suitable etch. For example, a stead cleavage # 2 consisting of:

200 g distilled water

800 g ethyl alcohol 96% g hydrochloric acid 37% g magnesium chloride 50 g copper chloride

After etching, a copper layer is formed on the surface of the metallographic sample, which must then be washed off with ammonia or copper chloride solution:

g distilled water g ethyl alcohol 96%

44.5 g hydrochloric acid 37% g copper (II) chloride

After etching, the sample is rinsed with alcoholic hydrochloric acid and wiped with alcohol with petrol, other alloys are etched with a solution of alkaline sodium picrate:

g distilled water g sodium hydroxide 2 g crystalline picric acid

Preparation of the solution: dissolve the sodium hydroxide in distilled water and heat on a water-bath to near boiling point, then add picric acid and make up to 100 ml with water. Etching time at 60 to 100 ° C for 15 to 30 minutes.

These methods have a number of disadvantages. It is the deposition of a copper layer on the surface of the samples, which must then be washed, thereby extending the time for evaluating the macro or microstructure, expensive ethyl alcohol or the use of picric acid, which is explosive.

These disadvantages of the previously known etchings are overcome by the etch of the invention, based on hydrochloric acid, nitric acid and water, which consists in that it consists of:

0.5 to 3.0 parts of pure magnesium chloride

1.0 to 10.0 parts pure aluminum chloride

3.0 to 15.0 parts pure copper-ammonium chloride

3.0 to 9.0 parts pure copper sulfate

5.5 to 16.5 parts of hydrochloric acid 37%

2.7 to 13.5 parts of 65% nitric acid

100 parts distilled water / parts are parts by weight /

An advantage of the etching agent according to the invention is also its simple and undemanding preparation, its stability and easy way of etching without subsequent washing of copper-plated samples with ammonia, because the etching agent according to the invention that don't mind observing or photographing the structure. Since the etch according to the invention is free of ethyl alcohol, it is also cost effective. A sample of the material to be examined for microstructure is immersed in the prepared solution for 1 to 3 seconds after polishing. After rinsing, the sample is ready for metallographic evaluation.

Optimal etching composition:

g of copper ammonium chloride pure 5 g of aluminum chloride pure 2 g of magnesium chloride pure g of copper sulphate pure

13.5 g nitric acid 65%

26.6 g hydrochloric acid 37%

200 g distilled water

Etching time for 2 seconds at 20 ° C.

Claims (2)

SUBJECT OF THE INVENTION An etching agent for developing the microstructure of ferrous and non-ferrous alloys based on hydrochloric acid, nitric acid and water, characterized in that it consists of: 0.5 to 3.0 parts of magnesium chloride pure 1.0 to 10.0 parts of aluminum chloride pure 3.0 to 15.0 parts of copper ammonium chloride pure 3.0 to 9.0 parts of copper sulfate pure 5.5 to 3.0 16.5 parts of hydrochloric acid 37% 2.7 to 13.5 parts of 65% nitric acid 100 parts of distilled water, said parts being parts by weight.