US2962391A - Method of chromizing - Google Patents
Method of chromizing Download PDFInfo
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- US2962391A US2962391A US799479A US79947959A US2962391A US 2962391 A US2962391 A US 2962391A US 799479 A US799479 A US 799479A US 79947959 A US79947959 A US 79947959A US 2962391 A US2962391 A US 2962391A
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- United States
- Prior art keywords
- hydrazine
- chromizing
- chromium
- articles
- retort
- Prior art date
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- 238000005254 chromizing Methods 0.000 title claims description 25
- 238000000034 method Methods 0.000 title claims description 18
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 claims description 36
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 17
- 229910052804 chromium Inorganic materials 0.000 claims description 17
- 239000011651 chromium Substances 0.000 claims description 17
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 2
- 229910000604 Ferrochrome Inorganic materials 0.000 description 16
- 239000012190 activator Substances 0.000 description 12
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 229910000831 Steel Inorganic materials 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- LIAWOTKNAVAKCX-UHFFFAOYSA-N hydrazine;dihydrochloride Chemical compound Cl.Cl.NN LIAWOTKNAVAKCX-UHFFFAOYSA-N 0.000 description 6
- BIVUUOPIAYRCAP-UHFFFAOYSA-N aminoazanium;chloride Chemical compound Cl.NN BIVUUOPIAYRCAP-UHFFFAOYSA-N 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 4
- 238000009835 boiling Methods 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 229910017604 nitric acid Inorganic materials 0.000 description 4
- 238000005121 nitriding Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 238000010926 purge Methods 0.000 description 4
- 238000005245 sintering Methods 0.000 description 4
- BKBQJEGATMJTIY-UHFFFAOYSA-N 2-(bromomethyl)benzoyl bromide Chemical compound BrCC1=CC=CC=C1C(Br)=O BKBQJEGATMJTIY-UHFFFAOYSA-N 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 230000001603 reducing effect Effects 0.000 description 3
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- -1 ammonium halides Chemical class 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 229910000039 hydrogen halide Inorganic materials 0.000 description 2
- 239000012433 hydrogen halide Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 1
- 229910000952 Be alloy Inorganic materials 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 229910000677 High-carbon steel Inorganic materials 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- SWLVFNYSXGMGBS-UHFFFAOYSA-N ammonium bromide Chemical compound [NH4+].[Br-] SWLVFNYSXGMGBS-UHFFFAOYSA-N 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- YRCOVWZYJNSHFM-UHFFFAOYSA-N hydrazine Chemical compound NN.NN.NN YRCOVWZYJNSHFM-UHFFFAOYSA-N 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- 239000011630 iodine Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000004071 soot Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 238000013022 venting Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- 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
- C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
- C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
- C23C10/34—Embedding in a powder mixture, i.e. pack cementation
- C23C10/36—Embedding in a powder mixture, i.e. pack cementation only one element being diffused
- C23C10/38—Chromising
- C23C10/40—Chromising of ferrous surfaces
- C23C10/42—Chromising of ferrous surfaces in the presence of volatile transport additives, e.g. halogenated substances
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S428/00—Stock material or miscellaneous articles
- Y10S428/922—Static electricity metal bleed-off metallic stock
- Y10S428/9335—Product by special process
- Y10S428/938—Vapor deposition or gas diffusion
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
- Y10T428/12771—Transition metal-base component
- Y10T428/12806—Refractory [Group IVB, VB, or VIB] metal-base component
- Y10T428/12826—Group VIB metal-base component
- Y10T428/12847—Cr-base component
- Y10T428/12854—Next to Co-, Fe-, or Ni-base component
Definitions
- the present invention relates to the chromizing of ferrous metal articles.
- a purpose of the invention is to improve the operation of chromizing iron and steel parts by reducing to an extent not heretofore possible the quantity of moisture which is present by employing activators or catalysts which do not have a tendency to pick up moisture.
- a further purpose is .to employ an activator which is free from the presence of carbon and has no tendency therefore to deposit soot or tan or .to carburize the work.
- a further purpose is to employ an activator which is a very powerful reducing agent and will tend to reduce oxide on the surface of the work and efiFectively purge the chromizing chamber of oxygen ,and maintain it free from oxygen.
- a further purpose is to avoid the presence of appreciable quantities of ammonia during chromizing so as to eliminate any nitriding which might otherwise occur.
- a further purpose is to utilize a chromizing activator which is a powder rather than a liquid or gas at room temperature.
- a further purpose is to secure chromizing by usetof .an activator which does not sublime or deposit on cool parts and does not tend to clog openings and ports in the chromizing chamber.
- a further purpose is to obtain an improved chromizing coating.
- a further purpose is to avoid sintering of chromium or ferrochrome on the surface of the Work.
- Extensive use has .been made in the prior art of chromizing using as an activator chlorine and hydrogen, or hydrogen chloride gas, or gases containing a halide and ammonia obtained, for example, by decomposing ammonium chloride, ammonium bromide or the like.
- chromizing is accomplished using as .an activator or catalyst one-or more of the hydrohalides of hydrazine such as hydrazine monohydrochloride N I-I .HCI, hydrazine dihydrochloride N H Z'HCI, and the corresponding compounds of bromine, fluorine and iodine.
- the hydrazine hydrochlorides are nonhydroscopic, and therefore can be used without danger that they will pick up moisture and give it forth when the retort is heated. This is important because the presence of moisture may tend to oxidize the work, and to impair the chromizing results or else increase the consumption of chromium by oxidation.
- hydrazine hydrohalides are heated, one of the products is dry hydrogen halide, which is very desirable as a chromizing carrier.
- hydrazine hydrohalides such as hydrazine monohydrochloride, hydrazine dihydrochloride and hydrazine monohydrobromide are solid powders at room temperature, and therefore they are much more convenient and safe to handle than liquids orgases which have been used as activators in some of the chromizing processes.
- the hydrazine hydrohalides have another property which is very valuable. They are very powerful reducing agents, and liberate hydrogen halide at low temperatures. They also liberate dry nitrogen and hydrogen. There is thus a strong reducing effect which tends to eliminate oxide films from the work and from the ferrochrome or other source of chromium. The nitrogen and hydrogen tend to purge air out of the retort and keep the retort free from air. Allof this is accomplished without any deleterious effect which would result if the activator contained carbon or oxygen.
- An improved feature of the invention is that nitriding of the work is reduced.
- ammonium halides are used as activators ammonia is present and this under some conditions causes nitriding which tends toward reduction in ductility of the coating.
- Hydrazine hydrohalides on the other hand when heated dry do not produce appreciable quantities of ammonia, and do not appear to have an appreciable nitriding effect.
- hydrazine hydrohalides as activators is that they break down at relatively low temperatures and therefore purge out the air from the retort at very low temperature, thus reducing the likelihood that the work or the ferrochrome will become oxidized from air in the retort before the retort is purged.
- a further advantage of hydrazine hydrohalides is that unlike ammonium halides they do not tend to sublime and condense on colder parts of the retort, with the danger of clogging a bleeder pipe or depositing coatings which must subsequently be removed on surfaces involved in sealing the retort.
- the reason for this different behavior from the ammonium salts is that hydrazine cannot be formed directly from elemental hydrogen and nitrogen.
- One of the great advantages of the present invention is that the work is not likely to have chromium or ferrochrome sintered to thesurface, ashas frequently occurred in priorart processes.
- hydrazine dihydrohalide is preferred to hydrazine .monohydrohalide because the presence of the extra amount of hydrohalogen appears to accomplish purging more effectively at low temperature, and also produces a larger amount'of carrier gas per mole of .activator. In addition, the ductility of .the chromized coating is superior.
- the process of the invention may be carried out in any suitable retort which excludes .the .atmosphere such as that of Samuel US. Patent 2,844,273, granted July .22, 1958, for Container for Articles Under Heat Treatment, or Samuel US. Patent 2,855,332, granted October 7, 1958, for Method of Chromizing Ferrous Metal.
- the retort is suitably provided with means for venting excess gas, while preventing air from entering as described in the above patents and patent application.
- the work will suitably be steel such as plain carbon low carbon steel, for example AISI 1005 or AISI 1010; plain carbon intermediate carbon steel such as AISI 1035 or AISI 1045; or plain carbon high carbon steel such as AISI 1065 or AISI 1090.
- the work may also be alloy steel such as AISI 4320, AISI 8640 or AISI 2340.
- the work may also be high carbon high chromium steel such as AISI 440 C.
- chromium or ferrochrome such as the grade which contains nominally 63 to 65 percent chromium and preferably with a low carbon content (less than 0.01% weight.
- the quantity of hydrazine hydrohalide should be between 0.01 and 2 percent by weight of the charge (work plus chromium or ferrochrome), preferably between 0.1 and 1 percent and most desirably 0.5 percent.
- the work may be packed in the chromium or ferrochrome, or the chromium or ferrochrome may be placed on the retort separately and spaced from the work.
- the work may be stationary or may be subject to turning or agitating, as described in the application above referred to.
- the work may be in contact with the chromium or it may be out of contact with the chromium.
- the chromium or ferrochrome may be in powder form, such as through 50 mesh or through 200 mesh per linear inch, but it will preferably be granular, having a particle size suitably in the range from 5 inch to inch and preferably about ,4; inch in diameter.
- the temperature range for chromizing will be between 1600 and 2300 F. and it will be evident that the results obtained in the examples given below are obtained also at other temperatures than this range at rates which will vary with the temperature.
- the time for chromizing in accordance with the invention will be in excess of 30 minutes at a temperature within the chromizing range set forth above, and preferably of the order of 1 to 4 hours. Chromizing for periods as long as 24 hours or longer is sometimes desirable.
- Example I A charge of 30 grams of hydrazine monohydrochloride, 7 pounds of ferrochrome of /s inch particle size, and two pounds of steel parts A181 1010, 0.032" thick was placed in a stationary sealed retort with the ferrochrome in contact with the steel parts and with a bleeder tube extending out beneath water. The retort was heated to 2100 F. and maintained at that temperature for one hour.
- the case depth was 0.003 inch.
- the case was ductile.
- the finish was bright and clean and there was no sintering of ferrochrome on the work.
- the case was resistant to boiling nitric acid (20 percent by weight).
- Example II A charge of 30 grams of hydrazine dihydrochloride NH NH ZHCI, or N H .2HCl, 7 pounds of ferrochrome as above set forth and 2 pounds of steel parts as above set forth was placed in a retort in accordance with EX- ample I. The retort was heated to 2100 F. and held at this temperature for one hour.
- the case depth was 0.003 inch.
- the case was very ductile, much more so than in Example I.
- the case resisted boiling nitric acid (20 percent by weight).
- the finish was excellent, showing no sintering and was bright.
- Example Ill The procedure of Example II was repeated using 20 grams of hydrazine dihydrochloride and 3 pounds of ferrochrome of A particle size. The results were the same as those in Example II.
- Example IV Into the chromizing retort was placed 20 grams of hydrazine dihydrochloride, 3 pounds of mesh ferrochrome powder and 4 pounds of AISI 1070 chain saw links. The retort was heated to 1900 F. and held at this temperature for two hours. The chromized layer was 0.001 to 0.0015 inch thick, glass hard, shiny and bright, and withstood 20 percent boiling nitric acid.
- Example V Into the retort was placed 30 grams of hydrazine monohydrobromide, 7 pounds of inch particles of ferrochrome and 2 pounds of AISI 1010 steel parts. Chromizing was carried on at 2100 F. for one hour.
- the case depth was 0.002 inch, the case ductility was fair, and the finish was bright, smooth and uniform with no sintering.
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Description
Nov. 29, 1960 G. A. SAMUEL ETAL 2,962,391
METHOD OF CHROMIZING Filed March 16, 1959 CHROMIZED STEEL PARTS United States Patent METHGD 0F :CHROMIZING Del.
Filed Mar. 1t, 1959, Ser. No. 799,419
8 Claims. {(1 '117--l07) The present invention relates to the chromizing of ferrous metal articles.
A purpose of the invention is to improve the operation of chromizing iron and steel parts by reducing to an extent not heretofore possible the quantity of moisture which is present by employing activators or catalysts which do not have a tendency to pick up moisture.
A further purpose is .to employ an activator which is free from the presence of carbon and has no tendency therefore to deposit soot or tan or .to carburize the work.
A further purpose is to employ an activator which is a very powerful reducing agent and will tend to reduce oxide on the surface of the work and efiFectively purge the chromizing chamber of oxygen ,and maintain it free from oxygen.
A further purpose is to avoid the presence of appreciable quantities of ammonia during chromizing so as to eliminate any nitriding which might otherwise occur.
A further purpose is to utilize a chromizing activator which is a powder rather than a liquid or gas at room temperature.
A further purpose is to secure chromizing by usetof .an activator which does not sublime or deposit on cool parts and does not tend to clog openings and ports in the chromizing chamber.
A further purpose is to obtain an improved chromizing coating.
A further purpose is to avoid sintering of chromium or ferrochrome on the surface of the Work.
Further purposes appear in the specification and in the claims.
A flow chart is shown in the drawing.
Extensive use has .been made in the prior art of chromizing using as an activator chlorine and hydrogen, or hydrogen chloride gas, or gases containing a halide and ammonia obtained, for example, by decomposing ammonium chloride, ammonium bromide or the like.
Results in some of the prior art processes have been erratic, and .the operations have often been inconvenient and needlessly expensive.
In accordance with the present invention, chromizing is accomplished using as .an activator or catalyst one-or more of the hydrohalides of hydrazine such as hydrazine monohydrochloride N I-I .HCI, hydrazine dihydrochloride N H Z'HCI, and the corresponding compounds of bromine, fluorine and iodine.
A number of distinct advantages are obtained by the use of these materials.
The hydrazine hydrochlorides are nonhydroscopic, and therefore can be used without danger that they will pick up moisture and give it forth when the retort is heated. This is important because the presence of moisture may tend to oxidize the work, and to impair the chromizing results or else increase the consumption of chromium by oxidation. When hydrazine hydrohalides are heated, one of the products is dry hydrogen halide, which is very desirable as a chromizing carrier.
The hydrazine hydrohalides such as hydrazine monohydrochloride, hydrazine dihydrochloride and hydrazine monohydrobromide are solid powders at room temperature, and therefore they are much more convenient and safe to handle than liquids orgases which have been used as activators in some of the chromizing processes.
The hydrazine hydrohalides have another property which is very valuable. They are very powerful reducing agents, and liberate hydrogen halide at low temperatures. They also liberate dry nitrogen and hydrogen. There is thus a strong reducing effect which tends to eliminate oxide films from the work and from the ferrochrome or other source of chromium. The nitrogen and hydrogen tend to purge air out of the retort and keep the retort free from air. Allof this is accomplished without any deleterious effect which would result if the activator contained carbon or oxygen.
An improved feature of the invention is that nitriding of the work is reduced. When ammonium halides are used as activators ammonia is present and this under some conditions causes nitriding which tends toward reduction in ductility of the coating. Hydrazine hydrohalides on the other hand when heated dry do not produce appreciable quantities of ammonia, and do not appear to have an appreciable nitriding effect.
.One of the great advantages of hydrazine hydrohalides as activators is that they break down at relatively low temperatures and therefore purge out the air from the retort at very low temperature, thus reducing the likelihood that the work or the ferrochrome will become oxidized from air in the retort before the retort is purged.
A further advantage of hydrazine hydrohalides is that unlike ammonium halides they do not tend to sublime and condense on colder parts of the retort, with the danger of clogging a bleeder pipe or depositing coatings which must subsequently be removed on surfaces involved in sealing the retort. The reason for this different behavior from the ammonium salts is that hydrazine cannot be formed directly from elemental hydrogen and nitrogen.
One of the great advantages of the present invention is that the work is not likely to have chromium or ferrochrome sintered to thesurface, ashas frequently occurred in priorart processes.
The use of hydrazine dihydrohalide is preferred to hydrazine .monohydrohalide because the presence of the extra amount of hydrohalogen appears to accomplish purging more effectively at low temperature, and also produces a larger amount'of carrier gas per mole of .activator. In addition, the ductility of .the chromized coating is superior.
The process of the invention may be carried out inany suitable retort which excludes .the .atmosphere such as that of Samuel US. Patent 2,844,273, granted July .22, 1958, for Container for Articles Under Heat Treatment, or Samuel US. Patent 2,855,332, granted October 7, 1958, for Method of Chromizing Ferrous Metal. The retort is suitably provided with means for venting excess gas, while preventing air from entering as described in the above patents and patent application. The work will suitably be steel such as plain carbon low carbon steel, for example AISI 1005 or AISI 1010; plain carbon intermediate carbon steel such as AISI 1035 or AISI 1045; or plain carbon high carbon steel such as AISI 1065 or AISI 1090. The work may also be alloy steel such as AISI 4320, AISI 8640 or AISI 2340. The work may also be high carbon high chromium steel such as AISI 440 C.
As a source of chromium we will use either chromium or ferrochrome such as the grade which contains nominally 63 to 65 percent chromium and preferably with a low carbon content (less than 0.01% weight.
The quantity of hydrazine hydrohalide should be between 0.01 and 2 percent by weight of the charge (work plus chromium or ferrochrome), preferably between 0.1 and 1 percent and most desirably 0.5 percent.
The work may be packed in the chromium or ferrochrome, or the chromium or ferrochrome may be placed on the retort separately and spaced from the work. The work may be stationary or may be subject to turning or agitating, as described in the application above referred to.
The work may be in contact with the chromium or it may be out of contact with the chromium.
The chromium or ferrochrome may be in powder form, such as through 50 mesh or through 200 mesh per linear inch, but it will preferably be granular, having a particle size suitably in the range from 5 inch to inch and preferably about ,4; inch in diameter.
The temperature range for chromizing will be between 1600 and 2300 F. and it will be evident that the results obtained in the examples given below are obtained also at other temperatures than this range at rates which will vary with the temperature.
The time for chromizing in accordance with the invention will be in excess of 30 minutes at a temperature within the chromizing range set forth above, and preferably of the order of 1 to 4 hours. Chromizing for periods as long as 24 hours or longer is sometimes desirable.
carbon), by
Example I A charge of 30 grams of hydrazine monohydrochloride, 7 pounds of ferrochrome of /s inch particle size, and two pounds of steel parts A181 1010, 0.032" thick was placed in a stationary sealed retort with the ferrochrome in contact with the steel parts and with a bleeder tube extending out beneath water. The retort was heated to 2100 F. and maintained at that temperature for one hour.
The case depth was 0.003 inch. The case was ductile. The finish was bright and clean and there was no sintering of ferrochrome on the work. The case was resistant to boiling nitric acid (20 percent by weight).
Example II A charge of 30 grams of hydrazine dihydrochloride NH NH ZHCI, or N H .2HCl, 7 pounds of ferrochrome as above set forth and 2 pounds of steel parts as above set forth was placed in a retort in accordance with EX- ample I. The retort was heated to 2100 F. and held at this temperature for one hour.
The case depth was 0.003 inch. The case, however, was very ductile, much more so than in Example I. The case resisted boiling nitric acid (20 percent by weight).
The finish was excellent, showing no sintering and was bright.
Example Ill The procedure of Example II was repeated using 20 grams of hydrazine dihydrochloride and 3 pounds of ferrochrome of A particle size. The results were the same as those in Example II.
Example IV Into the chromizing retort was placed 20 grams of hydrazine dihydrochloride, 3 pounds of mesh ferrochrome powder and 4 pounds of AISI 1070 chain saw links. The retort was heated to 1900 F. and held at this temperature for two hours. The chromized layer was 0.001 to 0.0015 inch thick, glass hard, shiny and bright, and withstood 20 percent boiling nitric acid.
Example V Into the retort was placed 30 grams of hydrazine monohydrobromide, 7 pounds of inch particles of ferrochrome and 2 pounds of AISI 1010 steel parts. Chromizing was carried on at 2100 F. for one hour.
The case depth was 0.002 inch, the case ductility was fair, and the finish was bright, smooth and uniform with no sintering.
The case withstood boiling nitric acid (20 percent by weight).
Similar results are obtained from the other hydrazine hydrohalides.
In view of our invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of our invention without copying the process shown, and we, therefore, claim all such insofar as they fall within the reasonable spirit and scope of our claims.
Having thus described our invention what we claim is new and desire to secure by Letters Patent is:
1. The process of chromizing ferrous metal articles,
which comprises placing the articles in a closed space from the hydrazine hydrohalide and maintaining the articles at a temperature within the temperature range set forth for a time of at least 30 minutes.
2. The process of claim 1, in which the hydrazine hydrohalide is a monohydrohalide.
3. The process of claim 1, in which the hydrazine hydrohalide is dihydrohalide.
4. The process of claim 1, in which the chromium is in contact with the articles.
5. The process of claim 1, in which the chromium is not in contact with the articles.
6. The process of claim 1, in which the hydrohalide is hydrazine monohydrochloride.
7. The process of claim 1, in which the hydrohalide is hydrazine dihydrochloride.
8. The process of claim 1, in which the hydrohalide is hydrazine monohydrobromide.
hydrazine hydrazine hydrazine References Cited in the file of this patent UNITED STATES PATENTS 2,930,106 Wrotnowski Mar. 29, 1960 FOREIGN PATENTS 7 722,797 Great Britain Feb. 2, 1955
Claims (1)
1. THE PROCESS OF CHROMIZING FERROUS METAL ARTICLES, WHICH COMPRISES PLACING THE ARTICLES IN A CLOSED SPACE CONTAINING CHROMIUM AND BETWEEN 0.1 AND 2 PERCENT OF HYDRAZINE HYDROHALIDE ON THE WEIGHT OF THE CHARGE AND HEATING THE ARTICLES, THE CHROMIUM AND THE HYDRAZINE HYDROHALIDE TO A TEMPERATURE OF 1600 TO 2300*F. WHILE SURROUNDING THE ARTICLES BY A GAS ATMOSPHERE EVOLVED FROM THE HYDRAZINE HYDROHALIDE AND MAINTAINING THE ARTICLES AT A TEMPERATURE WITHIN THE TEMPERATURE RANGE SET FORTH FOR A TIME OF AT LEAST 30 MINUTES.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US799479A US2962391A (en) | 1959-03-16 | 1959-03-16 | Method of chromizing |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US799479A US2962391A (en) | 1959-03-16 | 1959-03-16 | Method of chromizing |
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US2962391A true US2962391A (en) | 1960-11-29 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US799479A Expired - Lifetime US2962391A (en) | 1959-03-16 | 1959-03-16 | Method of chromizing |
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Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3222212A (en) * | 1962-11-29 | 1965-12-07 | Alloy Surfaces Co Inc | Process for chromizing |
US3353936A (en) * | 1962-11-29 | 1967-11-21 | Alloy Surfaces Co Inc | Chromized ferrous article |
US3403988A (en) * | 1963-12-16 | 1968-10-01 | Du Pont | Chromized metal substrate |
US3717444A (en) * | 1970-12-14 | 1973-02-20 | Inland Steel Co | Chromized steel product |
US6582765B2 (en) * | 2000-06-29 | 2003-06-24 | Borgwarner, Inc. | Carbide coated steel articles and method of making them |
US20060094551A1 (en) * | 2004-11-04 | 2006-05-04 | Tsubakimoto Chain Co. | Silent chain and method of producing same |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB722797A (en) * | 1950-11-21 | 1955-02-02 | Diffusion Alloys Ltd | Improvements in or relating to coating metals |
US2930106A (en) * | 1957-03-14 | 1960-03-29 | American Felt Co | Gaskets |
-
1959
- 1959-03-16 US US799479A patent/US2962391A/en not_active Expired - Lifetime
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB722797A (en) * | 1950-11-21 | 1955-02-02 | Diffusion Alloys Ltd | Improvements in or relating to coating metals |
US2930106A (en) * | 1957-03-14 | 1960-03-29 | American Felt Co | Gaskets |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3222212A (en) * | 1962-11-29 | 1965-12-07 | Alloy Surfaces Co Inc | Process for chromizing |
US3353936A (en) * | 1962-11-29 | 1967-11-21 | Alloy Surfaces Co Inc | Chromized ferrous article |
US3403988A (en) * | 1963-12-16 | 1968-10-01 | Du Pont | Chromized metal substrate |
US3717444A (en) * | 1970-12-14 | 1973-02-20 | Inland Steel Co | Chromized steel product |
US6582765B2 (en) * | 2000-06-29 | 2003-06-24 | Borgwarner, Inc. | Carbide coated steel articles and method of making them |
US20060094551A1 (en) * | 2004-11-04 | 2006-05-04 | Tsubakimoto Chain Co. | Silent chain and method of producing same |
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