US1808355A

US1808355A - Method of nitrification

Info

Publication number: US1808355A
Application number: US362447A
Authority: US
Inventors: Augustus B Kinzel
Original assignee: ELECTRO METALLURG CO
Current assignee: ELECTRO METALLURG CO; ELECTRO METALLURGICAL Co
Priority date: 1929-05-11
Filing date: 1929-05-11
Publication date: 1931-06-02
Anticipated expiration: 1948-06-02

Description

Patented June 2, 1931 UNITED STATES "PATENTI'OFFICE- A AUGUSTUS B. KI'NZEL, OF IBEECHHURST, NEW YORK, ASSIGNOB TO ELECTRO METAL- LURGICAL COMPANY A CORPORATION OF WEST VIRGINIA 7 METHOD or mrarrrcn'rron No Drawing. Application filed May 11,

This invention relates to the production of thin layers of hard, wear-resistant, nitrogencontaining material on ferrous articles.

The production of a hard, adherent, wear resistant skin or case of nitrogen-containing material on the surface of ferrous articles which contain certain alloy constituents by heating the articles in the presence of-am; monia at comparatively low temperatures is known. For example, the case is commonly produced on aluminum-containing ferrous alloys which contain critical amounts of alumi- 1111111 but the presence of other alloy constituents in critical amounts will produce nitrogen-containing wear-resistant cases on ferrous materials. To produce the case, the alloys may be heated in atmospheres of dry gaseous nitrogenous substances, such as ammonia, which give up nitrogen to the alloys. The temperatures generally used are about 450 C. to about 580 0., but other temperatures may be used. For the best results this process requires a treatment of fifteen to ninety hours at these temperatures in an atmosphere of ammonia to produce a wearresistant nitrogen-containing skin of the re-f quired thiclmess. The time consumed in such a treatment necessitates a large amount of apparatus per unit of product and. makes the process of nitrification costly. Where large articles are treated or a number of articles areltreated together in the same container, :1 lack of uniformity of nitrification is a common occurrence. More rapid methods of pro,- ducing the wear-resistant coatings and methods of producing more uniform coatings are desire i It has been found that by covering or embedding the alloy article with non-metallic inert porous material and then heating in the above described atmospheres, the lack of uniformity described above is avoided and the rate of nitrification is greatly accelerated. The inert materials used are those which are infusible or do not decompose atthe treating temperatures and which have no material effect on the alloys or ferrous materials when they are heated to the treatingtemperatures and ammonia is not present. The state of 1929. Serial No. 362,447.

rate of nitrification but comparatively coarse aggregates as well as extremely fine powders maybe used. The presence of the inert-material increases the rate of penetration of the nitrogen-containing case as well as the rate of formationof the nitrogen-containing case, but the exact nature of the action of the inert material is unknown to me.

Inert material in the form of powder which is fine enough to conform to the irregularities of the article is preferred. The inert material may be calcined, if desired, to remove the last traces of water, but this is not necessary where harmful amounts of water are not present. Experience has shown that powdered carhongnagnesia, silica or asbestos give exceptionally good results, but other inert ,,materials, such as other alkaline earth oxides may be used.

hours. Upon cooling, the article was. found to have a uniform, thin, adherent, wear-re sisting, nitrogen-containing coating having a ha d'ness greater than that corresponding to 1000 Brinell.

An allo article like the article'described in Example was heated to'the same temperature in the presence of ammonia for four hours but without the'inert material. Substantially no hardening of the surface by nitrification was produced.

II. Articles were embedded in magnesia at the center and at the eight corners of a container and treated with ammonia as described in Example I. The differences in hardness of the surface layers of the articles were less thrltln the hardness corresponding to 10 Brine Articles of the same composition were similarly placed -in the same container and treated with ammonia for a time sufficient to produce a hard nitrogenous coating but without the inert material. The differences in hardness of the surface layers of the article were that corresponding to 300 Brinell.

My invention is not limited to the treatment of aluminum-containing steels. It has been found that the presence of the inert material accelerates the formation of the nitro-' gen-containing coatings on other steels amenable to case-hardening by nitrification.

Longer treatments produce thicker layers of nitrified material on the alloys. Thicker layers of nitrogen-containing material are produced with the same conditions of temperatures and time when the inert material vis present than when only ammonia is used.

- give up nitrogen to the article, and heating.

3. The method of producing nitrogen-containing coatings on an'alloy article which comprises-embedding the article in a closed container 1n powdered magnesia, passing into the container a gaseous substance which Wlll.

presence of ammonia at temperatures below about 580 (3., which comprises covering the surface to be hardened with porous inert non-metallic material and heating the arti- "cle at said temperatures for about four hours in the presence of a gaseous substance which will give up nitrogen to the article.

8. The method of producing wear-resistant nitrogen-containing coatings on ferrous articles containing a critical amount of alloy substance which will produce an adherent nitrogen-containing coating by heating in the presence of ammonia at temperatures below about 580 (1., which comprises covering the surface to be hardened with porous inert non-metallic material and heating the article at said temperatures for about four hours in the presence. of ammonia.

9. The method of producing Wear-resistant nitrogen-containing coatings on ferrous alloy articles containing a critical amount of alloy substance which will produce an adherent nitrogen-containing coating by heating in the presence of ammonia at temperatures below about 580 (3., which comprises covering the surface to behardened with powdered magnesia, andheating at said temperatures for about four hours in the presence of ammonla.

In testimony whereof, I affix my signature.

AUGUSTUS B. KINZEL.

give up nitrogen to the article, and heating iron which comprises heating the article in contact witha powder of inert non-metallic material and a gaseous substance which will give up nitrogen to the article.

5. The method of producing nitrogen-containing coatings on an alloy article containing iron which comprises heating the article in contact with a powder of inert non-metallic material and ammonia.

6. The method of producing nitrogen-containing coatings on an alloy article contain ing iron which comprises heating the article to tem ratures of about 450 C. toabout 580 in contact with a powder of inert non-metallic material and a gaseous substance which will give up nitrogen to the artig a 4. The method of PIOdllClIlgIlltIOgGIl-COII- taining coatings on an alloy' article contain-