US1970141A - Process for hardening iron, steel, and cast iron alloys by nitriding - Google Patents

Process for hardening iron, steel, and cast iron alloys by nitriding Download PDF

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Publication number
US1970141A
US1970141A US568209A US56820931A US1970141A US 1970141 A US1970141 A US 1970141A US 568209 A US568209 A US 568209A US 56820931 A US56820931 A US 56820931A US 1970141 A US1970141 A US 1970141A
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nitriding
ammonia
hardening
iron
steel
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US568209A
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Hengstenberg Otto
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Nitralloy Corp
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Nitralloy Corp
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces

Definitions

  • the invention relates to processes for hardening iron, steel, and cast iron, alloys by nitriding and has for its object to improve these processes in so far as a greater nitride depth is obtained than it was hitherto possible, as well as an increased hardness of the nitrided layer.
  • heated metal surfaces such as those of the alloys of iron, steel and cast iron that are suitable for nitriding, act catalytically upon ammonia gases contacted therewith thereby accelerating the dissociation of the ammonia.
  • certain of the metals used in constructing containers for nitriding act catalytically upon ammonia at nitriding temperatures.
  • the improved results above mentioned may be obtained by carrying out the nitriding in the presence of a metal oxide, such for example as cobalt oxide, which is decomposable under the conditions obtaining in the nitriding operation to yield the catalyst poison.
  • a metal oxide such for example as cobalt oxide
  • the articles to be hardened may, for example, be sprinkled with a thin layer of pulverized cobalt oxide and then nitrided in the usual way in a steam of ammonia at about 500 C., the cobalt oxide being reduced during the nitriding and the decomposition products acting as catalyst poisons.
  • a greater nitriding depth is produced than with a nitriding treatment of the same duration without the use of a catalyst poison.
  • the improvement which comprises treating such an alloy with ammonia gas at a nitriding temperature in the presence of a substance selected from the group consisting of cobalt oxide and cobalt sulphate.
  • the improvement which comprises treating such an alloy with ammonia gas at a nitriding temperature while contacting said alloy with finely divided cobalt oxide.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Description

Patented Aug. 14, 1934 UNITED STATES PATENT OFFICE PROCESS FOR HARDENING IRON, STEEL, AND CAST IRON ALLOYS BY NITRIDING No Drawing. Serial No. 1930 4 Claims.
The invention relates to processes for hardening iron, steel, and cast iron, alloys by nitriding and has for its object to improve these processes in so far as a greater nitride depth is obtained than it was hitherto possible, as well as an increased hardness of the nitrided layer.
It is known that heated metal surfaces such as those of the alloys of iron, steel and cast iron that are suitable for nitriding, act catalytically upon ammonia gases contacted therewith thereby accelerating the dissociation of the ammonia. Similarly, certain of the metals used in constructing containers for nitriding act catalytically upon ammonia at nitriding temperatures. At the same time, it has been found that better and more uniform nitriding results are obtained when the percentage dissociation of the ammonia gas passed over the surfaces intended to be nitrided is kept within certain advantageously within a range of about 30 to 40%. Owing to the catalytic eflect of the heated metal surfaces exposed to the ammonia it has been heretofore diflicult to control the percentage dissociation of the ammonia within the desired range except by increasing the rate of circulation of the ammonia through the nitriding container, and this method has proven relatively expensive because of the increased consumption of the ammonia. Furthermore, increase of the rate of circulation of the ammonia does not entirely prevent a higher percentage dissociation of the ammonia in the localized areas where the ammonia gas contacts with the hot metal surfaces of the articles being nitrided.
It has been found that substances which act as catalyst poisons in the manufacture of ammonia also serve to bring about an increase in the hardness and depth of the hardness layer in nitride hardening. These substances serve to inhibit the catalytic action of the metal surfaces upon the ammonia gas and thereby retard the decomposition of the ammonia. In this way control of the rate of decomposition of the ammonia through control of the nitriding temperature and the rate of the circulation of the ammonia is made certain.
Application October 10, 1931, 568,209. In Germany November 1,
The improved results above mentioned may be obtained by carrying out the nitriding in the presence of a metal oxide, such for example as cobalt oxide, which is decomposable under the conditions obtaining in the nitriding operation to yield the catalyst poison. I have also used cobalt sulphate with similar results.
In carrying the invention into efiect the articles to be hardened may, for example, be sprinkled with a thin layer of pulverized cobalt oxide and then nitrided in the usual way in a steam of ammonia at about 500 C., the cobalt oxide being reduced during the nitriding and the decomposition products acting as catalyst poisons. By this process with a given duration of the nitriding treatment, a greater nitriding depth is produced than with a nitriding treatment of the same duration without the use of a catalyst poison.
What I claim and desire to secure by Letters Patent is:-
1. In the art of hardening ferrous base alloys by nitriding, the improvement which comprises treating such an alloy with ammonia gas at a nitriding temperature in the presence of a substance selected from the group consisting of cobalt oxide and cobalt sulphate.
2. In the art of hardening ferrous base alloys by nitriding, the improvement which consists in nitriding such an alloy while contacting said alloy with a substance selected from the group consisting of cobalt oxide and cobalt sulphate.
by nitriding, the improvement which comprises treating such an alloy with ammonia gas at a nitriding temperature while contacting said alloy with finely divided cobalt oxide.
4. In the art of hardening ferrous base alloys by nitriding, the improvement which comprises treating such an alloy with ammonia gas at a nitriding temperature while contacting said alloy with finely divided cobalt sulphate.
O'I'I'O HENGSTENBERG.
3. In the art of hardening ferrous base alloys 1
US568209A 1930-11-01 1931-10-10 Process for hardening iron, steel, and cast iron alloys by nitriding Expired - Lifetime US1970141A (en)

Applications Claiming Priority (1)

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DE1970141X 1930-11-01

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