US1949682A - Nitriding - Google Patents

Description

Patented Mar. 6, 16934 NITBmING John J. Egan, Brooklyn, N. Y., assignor to Electl'o Metallurgical Company,

Virg a a corporation or West No Drawing. Application February 26, 1930, Serial No. 431,641

9 Claims. (Cl. 148-46) I My invention relates to the production of nitride cases on ferrous materials by heating the materials in the presence of nitriding agents, and it is the main object of my invention to intensify or accelerate the production of such cases.

Thin, hard, wear-resistant cases on ferrous alloys are useful as wearing surfaces for machine er-temperatures are used than when higher tem-' peratures are used. The hard, wear-resistantcases are usualy' produced by heating in an atmosphere of ammonia to about 460 C. to 580 C., the treated alloy containing a promoting agent, such as aluminum or vanadium, which promotes the formation of the hard, wear-resistant coating at these temperatures. By far the most extensive use of my invention is in connection with the production of hard, wear-resistant coatings and the invention will be described with reference thereto.

It has been found that the action of nitriding agents is intensified when a closed chain carbon compound in which nitrogen forms a part of the closed chain is present.

As illustrative of my invention, a specimen of ferrous alloy containing about 95.5% iron, about 1% aluminum, and small amounts oi phosphorus, sulphur, manganese, silicon, nickel, molybdenum and carbon was placed in a closed con tainer. Ammonia was bubbled through pyridine whichwas heated to a temperature just below its boiling point to increase its vapor pressure. The entrapped air in the container was displaced by the mixture of ammonia and pyridine vapor and the container and its contents were heated to 460 C. for 4 hours whilst a slow current of the gas mixture was passed into the container. A thin, uniform, wear-resistant case having a hardness corresponding to about 1000 Brinell was pro-. duced on the specimen. A similar hard, wearresistant case was producedon another specimen 0! the same alloy when heated for 16 hourswithout the presence of pyridine vapor. By treatment with ammonia without, the pyridine, no'

appreciable hardness was produced by heating the alloy at 460 C. for 4 hours.

Beneficial results may be produced by the use of other compounds of the above described class as for example, higher molecular weightclosedt ferrous materials which comprises heating the ammonia which comprises effecting said nitriding chain carbon compounds in which at least one nitrogen radical forms a part of a closed chain. Quinoline is such a compound, and is an effective accelerator, and other compounds in which a nitrogen atom occurs in a closed chainmay be used.

Any appreciable amount of the accelerator in conjunction with the nitriding agent is suflicient to produce acceleration. The preferred amount to be used with an alloy under given conditions may be determined by experiment for each particular case, but the invention is of course not restricted to the proportion which gives the maximum effect. Considerations of cost make it desirable not to use excessive amounts of the accelerator substance. That is, a modicum of accelerator is generally suflicient. Although I have given only a few specific examples of accelerators and only one example of a nitriding agent, it is evident that other substances of the classes described may beused and modifications of the described methods may be made without departing from my invention. Therefore, I do not wish to be understoodas imposing limitations on my invention except such as are imposed by the prior art and by the annexed claims.

Iclaim: 1. The method of producing nitride cases on material at nitriding temperatures below the eutectoid at about 600 C. in the presence of ammonia and an accelerating agent consisting of a closed chain carbon compound in which one a nitrogen radical and five carbon radicals form 0 the closed chain. i

2. Method of accelerating; the production of nitride cases on ferrous materials by heating the materials at nitriding temperatures below the nitride eutectoid at about 600 C. in the presence oi ammonia which comprises efiecting -said nitriding in the presence of an accelerating agent consisting of a closed chain carbon compound in which one nitrogen radical and iive carbon radicals form the closed chain.

3. Method of accelerating the production or nitride cases on ferrous materials by heating the materials at nitriding temperatures below the nitride eutectoid at about 600 C. in the presence of in. the presence of an acceleratingagent chosen from the group comprising pyrldineand quinoline.

4. The method of producing nitridecases' on ferrous materials which comprises heating the 5 material at nitriding temperatures below the nitride eutectoid at about 600 C. inthe presence of ammonia and at least one or the following: pyridine, quinoline.

5, Medium for nitriding ferrous materials comprising ammonia and a modicum of a nitriding accelerator, said accelerator consisting of a closed chain carbon compound in which one nitrogen atom and five carbon atoms form the closed i'errous materials which comprises passing ammonia in contact with at least one liquid closed and five carbon radicals form the closed chain, whereby a mix'tm'e oi the ammonia and the compound is iormed, and heating the material at nitriding temperatures below the nitride eutectoid atabout 600 C. in the presence of the mixture 9. The method of producing nitride cases on ferrous materials which comprises passing amchain compound in which one nitrogen radical monia in contact with at least one compound chosen from the group consisting 'of pyridine and quinoline, whereby a mixtin-e oi. the ammonia and the compoundis formed, and heating the material at nitriding temperatures below the nitride eutectoid at about 600 C. in the presence or the mixture. JOHN J. EGAN.

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