CA2055541A1 - Process for nitriding steel workpieces under pressure - Google Patents
Process for nitriding steel workpieces under pressureInfo
- Publication number
- CA2055541A1 CA2055541A1 CA 2055541 CA2055541A CA2055541A1 CA 2055541 A1 CA2055541 A1 CA 2055541A1 CA 2055541 CA2055541 CA 2055541 CA 2055541 A CA2055541 A CA 2055541A CA 2055541 A1 CA2055541 A1 CA 2055541A1
- Authority
- CA
- Canada
- Prior art keywords
- nitriding
- nitrogen
- volume
- ammonia
- pressure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
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
- 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
Landscapes
- 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)
Abstract
A b s t r a c t In gas nitriding under pressure, substantially non.
porous, thick nitride layers are obtained in a short time providing a mixture of 5 to 95% by volume ammonia and 95 to 5% by volume nitrogen is used and the nitriding process is carried out under a constant pressure above 0.2 MPa.
porous, thick nitride layers are obtained in a short time providing a mixture of 5 to 95% by volume ammonia and 95 to 5% by volume nitrogen is used and the nitriding process is carried out under a constant pressure above 0.2 MPa.
Description
2~5~
A process for nitriding steel workpieces under pressure Description:
This invention relates to processes for nitriding steel workpieces and in particular, to such processes in a gas atmosphere containing atomic nitrogen at temperatures above 425C and under pressures above 0.2 MPa.
At present, nitride layers are formed on workpieces of steel alloys in a salt bath, by gas nitriding or by plasma nitriding. These layers improve the resistance to corrosion, wear resistance and vibration resistance of the steels. They normally consist of a so-called coupling layer a few micrometres thick over a nitrogen diffusion layer which is generally formed by the above-mentioned processes over process times of the order of 100 hours.
In recent years, gas nitriding in particular has received a considerable impetus, the steel workpieces being heated in an atmosphere of nitrogen-releasing gases, preferably in an atmosphere of ammonia.
US-PS 2,779,697 describes a process for nitriding steels under pressure in gaseous ammonia.
In this process, a pressure vessel is filled with a certain quantity of ammonia and heated to temperatures of 425 to 640C (800 to 1,200F) so that an ammonia pressure of a few bar is built up in the pressure vessel. Nitride layers between 20 and 40 ~m thick are formed in about 15 hours, depending on the quantity of ammonia, the pressure and the temperature. However, this process has not been successfully used in practice.
Accordingly, the problem addressed by the present invention was to provide a process for nitriding steel workpieces in a gas atmosphere containing atomic nitrogen at temperatures above 425C and under pressures above 0.2 MPa, in which non-porous coupling layers up to 50 ~m in 2~aO~4 ~
thickness could be formed in a short time on unalloyed and alloyed steels without any need for speclal pretreatment.
According to the invention, the solution to this problem is characterized in that the gas atmosphere con-sists of 5 to 95% by volume ammonia and 95 to 5% by volume molecular nitrogen and in that nitriding is carried out under constant pressure.
Ammonia which dissociates into hydrogen and nitrogen at relatively high temperatures is used as the gas releas-ing atomic nitrogen. The use of pure ammonia without incorporation of molecular nitrogen leads to distinctly poorer coupling layers. In this way, nitriding layers up to 50 ~m thick are o~tained in 4 to 5 hours.
These coupling layers are substantially non-porous.
The ratio of the 7' phase to the ~ phase can be established through the process parameters and, in the most favorable case, is 100% ~ phase. Austenitic and high-chrome steels can be nitrided without any chemical pretreatment. This process is suitable for treating workpieces in any numbers and without any geometric restrictlon. The number is determined solely by the available furnace size. A chamber furnace can typically be heated to temperatures of up to 1,200C for an absolute internal pressure of 0.2 to 10 MPa.
~he treatment parameters of temperature, time, absolute pressure and partial pressure of the nitrogen-releasing gas -may be adJusteJ tG establish optimal treatment condl~lons for each material. Nitriding temperatures of 500 to 900C
have proved to be favourable. In addition, it is important that the entire nitriding process be carried out under constant pressure. Pressure variations adversely affect the favorable properties and reproducibility of the coup-ling layers. The treatment time is determined by the type of steel and the desired layer thickness.
The invention is illustrated by the following Ex-amples.
2~3 Example 1 A steel of the composition C 45 is nitrided with a gas mixture of 30% by volume ammonia and 70% by volume nitrogen in a pressure-tight chamber furnace under an excess pressure of 2 MPa and at a temperature of 700C. After one hour, a substantially non-porous 40 ~m thick coupling layer has formed.
Example 2 In the case of fast steels, a 100 ~m thick diffusion zone is obtained in 4 hours at 580C/l MPa pressure using a gas atmosphere of 80% by volume ammonia and 20% by volume nitrogen.
Example 3 A substantially non-porous 50 ~m thick coupling layer is obtained on a steel of the composition 16MnCr5 after 2 hours at 550C/8 MPa pressure in a gas atmosphere of 70% by volume ammonia and 30% by volume nitrogen.
A process for nitriding steel workpieces under pressure Description:
This invention relates to processes for nitriding steel workpieces and in particular, to such processes in a gas atmosphere containing atomic nitrogen at temperatures above 425C and under pressures above 0.2 MPa.
At present, nitride layers are formed on workpieces of steel alloys in a salt bath, by gas nitriding or by plasma nitriding. These layers improve the resistance to corrosion, wear resistance and vibration resistance of the steels. They normally consist of a so-called coupling layer a few micrometres thick over a nitrogen diffusion layer which is generally formed by the above-mentioned processes over process times of the order of 100 hours.
In recent years, gas nitriding in particular has received a considerable impetus, the steel workpieces being heated in an atmosphere of nitrogen-releasing gases, preferably in an atmosphere of ammonia.
US-PS 2,779,697 describes a process for nitriding steels under pressure in gaseous ammonia.
In this process, a pressure vessel is filled with a certain quantity of ammonia and heated to temperatures of 425 to 640C (800 to 1,200F) so that an ammonia pressure of a few bar is built up in the pressure vessel. Nitride layers between 20 and 40 ~m thick are formed in about 15 hours, depending on the quantity of ammonia, the pressure and the temperature. However, this process has not been successfully used in practice.
Accordingly, the problem addressed by the present invention was to provide a process for nitriding steel workpieces in a gas atmosphere containing atomic nitrogen at temperatures above 425C and under pressures above 0.2 MPa, in which non-porous coupling layers up to 50 ~m in 2~aO~4 ~
thickness could be formed in a short time on unalloyed and alloyed steels without any need for speclal pretreatment.
According to the invention, the solution to this problem is characterized in that the gas atmosphere con-sists of 5 to 95% by volume ammonia and 95 to 5% by volume molecular nitrogen and in that nitriding is carried out under constant pressure.
Ammonia which dissociates into hydrogen and nitrogen at relatively high temperatures is used as the gas releas-ing atomic nitrogen. The use of pure ammonia without incorporation of molecular nitrogen leads to distinctly poorer coupling layers. In this way, nitriding layers up to 50 ~m thick are o~tained in 4 to 5 hours.
These coupling layers are substantially non-porous.
The ratio of the 7' phase to the ~ phase can be established through the process parameters and, in the most favorable case, is 100% ~ phase. Austenitic and high-chrome steels can be nitrided without any chemical pretreatment. This process is suitable for treating workpieces in any numbers and without any geometric restrictlon. The number is determined solely by the available furnace size. A chamber furnace can typically be heated to temperatures of up to 1,200C for an absolute internal pressure of 0.2 to 10 MPa.
~he treatment parameters of temperature, time, absolute pressure and partial pressure of the nitrogen-releasing gas -may be adJusteJ tG establish optimal treatment condl~lons for each material. Nitriding temperatures of 500 to 900C
have proved to be favourable. In addition, it is important that the entire nitriding process be carried out under constant pressure. Pressure variations adversely affect the favorable properties and reproducibility of the coup-ling layers. The treatment time is determined by the type of steel and the desired layer thickness.
The invention is illustrated by the following Ex-amples.
2~3 Example 1 A steel of the composition C 45 is nitrided with a gas mixture of 30% by volume ammonia and 70% by volume nitrogen in a pressure-tight chamber furnace under an excess pressure of 2 MPa and at a temperature of 700C. After one hour, a substantially non-porous 40 ~m thick coupling layer has formed.
Example 2 In the case of fast steels, a 100 ~m thick diffusion zone is obtained in 4 hours at 580C/l MPa pressure using a gas atmosphere of 80% by volume ammonia and 20% by volume nitrogen.
Example 3 A substantially non-porous 50 ~m thick coupling layer is obtained on a steel of the composition 16MnCr5 after 2 hours at 550C/8 MPa pressure in a gas atmosphere of 70% by volume ammonia and 30% by volume nitrogen.
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for nitriding steel workpieces in a gas atmosphere containing atomic nitrogen at temperatures above 425°C and under pressures above 0.2 MPa, characterized in that the gas atmosphere consists of 5 to 95% by volume ammonia and 95 to 5% by volume molecular nitrogen and in that nitriding is carried out under constant pressure.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19904036381 DE4036381C1 (en) | 1990-11-15 | 1990-11-15 | |
DEP4036381.3 | 1990-11-15 |
Publications (1)
Publication Number | Publication Date |
---|---|
CA2055541A1 true CA2055541A1 (en) | 1992-05-16 |
Family
ID=6418307
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA 2055541 Abandoned CA2055541A1 (en) | 1990-11-15 | 1991-11-14 | Process for nitriding steel workpieces under pressure |
Country Status (9)
Country | Link |
---|---|
EP (1) | EP0485686A1 (en) |
JP (1) | JPH076053B2 (en) |
BR (1) | BR9101780A (en) |
CA (1) | CA2055541A1 (en) |
CS (1) | CS336091A3 (en) |
DE (1) | DE4036381C1 (en) |
PL (1) | PL289794A1 (en) |
RU (1) | RU2015197C1 (en) |
YU (1) | YU47730B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102994939A (en) * | 2013-01-07 | 2013-03-27 | 聊城市人和精工轴承有限公司 | Vacuum pulse nitriding process used for heat treatment of bearing cage |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5292555A (en) * | 1990-07-04 | 1994-03-08 | Degussa Aktiengesellschaft | Process for applying nitride layers to titanium |
DE4115135C1 (en) * | 1991-05-08 | 1992-02-27 | Degussa Ag, 6000 Frankfurt, De | |
CH690019A5 (en) * | 1992-07-16 | 2000-03-31 | Giroflex Entwicklungs Ag | Supporting frame for a chair, in particular for an adjustable in height and tilt office chair. |
TW237484B (en) * | 1992-09-16 | 1995-01-01 | Daido Oxygen | |
DE4333917C2 (en) * | 1993-10-05 | 1994-06-23 | Hans Prof Dr Ing Berns | Edge embroidery to create a high-strength austenitic surface layer in stainless steels |
FR2884879B1 (en) * | 2005-04-22 | 2007-08-03 | Stephanois Rech Mec | TORQUE OF GUIDE ARMS WHOSE ONE IS OF PARTICULAR STEEL LEADING TO IMPROVED PERFORMANCE. |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2779697A (en) * | 1955-09-26 | 1957-01-29 | United States Steel Corp | Method of nitriding metallic surfaces |
FR1319729A (en) * | 1962-04-12 | 1963-03-01 | P I M Prodotti Per L Ind Metal | Method and furnace for gas phase treatment, carburizing, nitriding and the like on metal parts |
GB1510158A (en) * | 1976-07-09 | 1978-05-10 | Rolls Royce Motors Ltd | Nitriding of steel |
GB2055404B (en) * | 1979-06-26 | 1983-02-16 | Lucas Industries Ltd | Gas nitriding steel |
-
1990
- 1990-11-15 DE DE19904036381 patent/DE4036381C1/de not_active Expired - Lifetime
-
1991
- 1991-03-16 EP EP91104103A patent/EP0485686A1/en not_active Ceased
- 1991-03-22 YU YU50691A patent/YU47730B/en unknown
- 1991-04-09 PL PL28979491A patent/PL289794A1/en unknown
- 1991-05-03 BR BR9101780A patent/BR9101780A/en not_active Application Discontinuation
- 1991-11-06 CS CS913360A patent/CS336091A3/en unknown
- 1991-11-12 JP JP29545091A patent/JPH076053B2/en not_active Expired - Fee Related
- 1991-11-14 RU SU5001982 patent/RU2015197C1/en active
- 1991-11-14 CA CA 2055541 patent/CA2055541A1/en not_active Abandoned
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102994939A (en) * | 2013-01-07 | 2013-03-27 | 聊城市人和精工轴承有限公司 | Vacuum pulse nitriding process used for heat treatment of bearing cage |
CN102994939B (en) * | 2013-01-07 | 2014-08-06 | 聊城市人和精工轴承有限公司 | Vacuum pulse nitriding process used for heat treatment of bearing cage |
Also Published As
Publication number | Publication date |
---|---|
RU2015197C1 (en) | 1994-06-30 |
PL289794A1 (en) | 1992-06-01 |
JPH04268063A (en) | 1992-09-24 |
DE4036381C1 (en) | 1991-08-14 |
CS336091A3 (en) | 1992-06-17 |
YU50691A (en) | 1993-11-16 |
JPH076053B2 (en) | 1995-01-25 |
EP0485686A1 (en) | 1992-05-20 |
BR9101780A (en) | 1992-06-23 |
YU47730B (en) | 1996-01-08 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
FZDE | Dead |