SU19014A1 - Method of protection from nitration of individual parts of the object being nitrated - Google Patents

Description

The proposed method, which relates to the known methods of coating individual places of products, in order to protect them from the action of reagents designed to change the composition of the surface layer of the product by diffusion with various metals, consists in covering the protected places of the product being nitrated with a tin layer on top of which the layer is applied liquid glass and aluminum powder.

The objects to be treated, in order to impart hardness to them by nitriding, are covered in those places that must be protected from this nitration with a layer of metal or alloy that protects these places from nitrogen penetration during the nitration process. As a reagent for this purpose, a tin layer or tin alloy is used, which is applied either in the usual way, or by immersing the object with protected places for a few minutes in a liquid tin

 a bath. The protection against the action of nitration thus obtained is opposed, as experiments have shown, several times to the repeated process of nitriding, so that I can subsequently be informed of the hardness of the place covered with tin, it is necessary to first remove the tin layer to a certain depth.

Since the melting point of tin or tin alloy is lower than the temperature at which the nitration process is carried out, tin or its alloy is melted during this process and sometimes drains to those parts of the object being processed that must undergo such processing. In order to avoid harmful effects, the tin-coated places are covered with a layer of soda glass and aluminum powder, letting this layer dry out well. I It is also possible, in order to avoid the indicated I disadvantages, omit the previously covered ones.

The tin or the entire object is heated to about 400 ° sodium or potassium nitrate, in which the tin is liquefied and, downstairs, cannot adhere to those places that were not previously covered with it. This is due to the fact that places not covered with tin after oxidation are easily oxidized and, in addition, tin droplets are covered with an oxide film, thereby not adhering to the surface of the object (slight oxidation of places not covered with tin does not prevent nitriding).

The subject of the patent.

1. A method of protecting from nitration of individual parts of an object to be nitrated by coating these parts with a layer of metal or alloy, characterized in that the places to be protected are covered with tin, on top of which a layer of liquid glass and aluminum powder is applied.

2. Modification of the method described in paragraph 1, characterized in that the tin-coated parts of the product or the whole product are immersed in a solution of sodium or potassium nitrate.