EP1333105A1 - Process and apparatus for heat treating metallic articles and heat treated article - Google Patents

Abstract

Process for heat treating metallic workpieces comprises: heating workpieces to a first temperature in a vacuum or in a neutral or reducing gas atmosphere; carburizing the workpieces at the first temperature reached at the end of the heating up phase; cooling the workpieces to a second temperature; boriding the workpieces; cooling the workpieces to third temperature; and quenching the workpieces. Process for heat treating metallic workpieces comprises: heating the workpieces to a first temperature in a vacuum or in a neutral or reducing gas atmosphere during the heating up phase; carburizing the workpieces at the first temperature reached at the end of the heating up phase and at a first pressure for a first time period in a gas atmosphere containing a hydrocarbon during an enriching phase next to the heating up phase; cooling the workpieces to a second temperature; boriding the workpieces; cooling the workpieces to a third temperature; and quenching the workpieces from the third temperature to a temperature of less than 150 degreesC. Independent claims are also included for the following: (a) a device for carrying out the heat treating process; and (b) a heat treated workpiece. Preferred Features: The workpieces are heated in the first step to 800-1100 degreesC and cooled to 800-950 degreesC. The workpieces are cooled to room temperature during quenching. During boriding, the gas atmosphere contains boron trichloride, boron trifluoride and/or diboran.

Description

The invention relates to a method for heat treatment of metallic Workpieces, in particular for the combined carburizing, boronizing and hardening of Ferrous materials. It also relates to a device by means of which a can carry out such procedure, and one by the procedure heat-treated workpiece.

To create defined workpiece properties, such as a high one Hardness or wear resistance, metallic workpieces are usually subjected to a thermochemical heat treatment. The goal of this Heat treatment is, for example, case hardening, the surface layer of the Carburizing workpieces first, i.e. enriching them with carbon in order to due to the resulting change in material composition the workpieces through a subsequent hardening a relatively high Hardness. Types of heat treatment are also known, in which the Surface of the work pieces with the required mechanical properties causing layer are coated. For example, at Boronize by diffusing boron a hard boride layer on the surface of the Workpieces produced that are highly wear and corrosion resistant of the workpieces.

A compilation of the most diverse types of heat treatment takes place for example in DIN 8580. The prior art also includes processes Known which individual types of heat treatment combine with each other. These so-called combination, hybrid or duplex processes are making themselves felt Use synergy effects when combining the different Types of heat treatment arise (see O. H. Kessler et al .: "Combinations of coating and heat treating processes: establishing a system for combined processes and examples ", Surface and Coatings Technology 108-109 (1998) pages 211 to 216; T. Bell et al .: "Realizing the potential of duplex surface engineering ", Tribology International Volume 31 Number 1 - 3 (1998) pages 127 to 137). In this way, the workpieces can be given properties that could not be achieved by the individual types of heat treatment alone. The workpieces can thus handle complex stresses, for example both a high fatigue strength and a high resistance to Wear and corrosion are sufficient.

Not every combination of different types of heat treatment calls however, a synergistic result emerges, as Bell et al. point out (loc. cit., Page 128). Conversely, has a positive effect in terms of having a hard one Workpieces with a surface, for example, the combination of CVD (Chemical Vapor Deposition) and quench hardening. Because, as Kessler et al. (a. a. O.) set out, in such a duplex process by the plasma-activated vapor deposition process generated surface layer over a high hardness.

The invention has for its object to provide a method and an apparatus for the heat treatment of metallic workpieces, by means of which a comparatively large strength, in particular time and fatigue strength, can be achieved with high wear resistance of the workpieces.

a) Erwärmen der Werkstücke auf eine erste Temperatur unter Vakuum oder in einer neutralen oder reduzierenden Gasatmosphäre während einer Aufheizphase;

b) Aufkohlen der Werkstücke bei der am Ende der Aufheizphase erreichten ersten Temperatur und einem ersten Druck für eine erste Zeitdauer in einer Kohlenwasserstoff enthaltenden Gasatmosphäre während einer sich unmittelbar an die Aufheizphase anschließenden Anreicherungsphase;

c) Abkühlen der Werkstücke von der ersten Temperatur auf eine zweite Temperatur unter Vakuum oder in einer hauptsächlich Stickstoff (N2) enthaltenden Gasatmosphäre während einer sich unmittelbar an die Anreicherungsphase anschließenden ersten Abkühlungsphase;

d) Borieren der Werkstücke bei der am Ende der ersten Abkühlungsphase erreichten zweiten Temperatur und einem zweiten Druck für eine zweite Zeitdauer in einer Bor (B) enthaltenden Gasatmosphäre während einer sich unmittelbar an die erste Abkühlungsphase anschließenden Borierungsphase;

e) Abkühlen der Werkstücke von der zweiten Temperatur auf eine dritte Temperatur unter Vakuum oder in einer hauptsächlich Stickstoff (N2) enthaltenden Gasatmosphäre während einer sich unmittelbar an die Borierungsphase anschließenden zweiten Abkühlungsphase und

f) Abschrecken der Werkstücke von der dritten Temperatur auf eine Temperatur unter 150 °C während einer sich an die zweite Abkühlungsphase anschließenden Abschreckphase.

To achieve this object, a method for the heat treatment of metallic workpieces, in particular for the combined carburizing, boronizing and hardening of iron materials, has the following method steps in accordance with claim 1:

a) heating the workpieces to a first temperature under vacuum or in a neutral or reducing gas atmosphere during a heating phase;

b) carburizing the workpieces at the first temperature and pressure reached at the end of the heating phase for a first period of time in a hydrocarbon-containing gas atmosphere during an enrichment phase immediately following the heating phase;

c) cooling the workpieces from the first temperature to a second temperature under vacuum or in a gas atmosphere containing mainly nitrogen (N2) during a first cooling phase immediately following the enrichment phase;

d) Boronizing the workpieces at the second temperature and a second pressure reached at the end of the first cooling phase in a gas atmosphere containing boron (B) for a second period of time during a boronation phase immediately following the first cooling phase;

e) cooling the workpieces from the second temperature to a third temperature under vacuum or in a gas atmosphere mainly containing nitrogen (N2) during a second cooling phase immediately following the boronation phase and

f) quenching the workpieces from the third temperature to a temperature below 150 ° C. during a quenching phase following the second cooling phase.

Such a method is based on the knowledge that the boronation phase can be used to control the during the enrichment phase in the Surface layer of the enriched carbon workpieces inside the To let workpieces diffuse. An independent diffusion phase for Generate the desired carbon content in the surface layer, as in the conventional carburizing is therefore unnecessary. Under carburizing in The above-mentioned sense is also to be understood as carbonitriding, if additional Nitrogen is added to the gas atmosphere.

An efficient process management also contributes to the fact that during the immediately following the enrichment phase Cooling phase temperature difference to be bridged is generally low is. Because the second temperature required for boronizing is about for most low-carbon iron materials, such as case hardening steel C 15, or not only slightly less than the first necessary for the enrichment phase Temperature. Depending on the application, the second temperature can also be higher than the first temperature, so the workpieces are not in this case are to be cooled but warmed up.

That during the enrichment phase and as a diffusion phase for the Carbon-serving boronation phase generated carbon profile in the Edge layer of the workpieces leads together with the final one Quenching to residual compressive stresses in the surface layer of the workpieces and thus to a time and fatigue strength, the relatively high dynamic Withstands loads. It also turns on during the boronation phase wear-resistant boride layer formed on the surface of the workpieces the final quenching of the workpieces is more resilient. Because that The carburized and hardened structure of the existing beneath the boride layer Workpieces have a sufficiently high hardness of usually approx. 800 HV, which in this way is a stable substructure for which usually a hardness according to Vickers of about 2000 boride layer. In contrast to such as a CVD process or PVD process (Physical Vapor Deposition) the risk of chipping of the hard boride layer with a high dynamic So there is no burden.

The first temperature at which the workpieces reach during the heating phase heated and where the workpieces carburized during the enrichment phase or carbonitrided, the second temperature at which the workpieces during exposed to the boronation phase, the third temperature from which the Workpieces are quenched, the length of the first period, the length of the second period and that in the enrichment phase and in the boronation phase the amounts of carbon and boron donating agents supplied depends primarily on the material of the workpieces to be treated, which for Reaching the desired carbon content in the surface layer of the workpieces required specific composition of the gas atmosphere and the desired treatment success, such as the desired carburization depth and Boride layer thickness. The of the material properties of the to be treated Workpiece dependent process parameters can be for a specific Material from generally accessible databases, such as Calphad (Calculation of Phase Diagrams). Depending on the application, it can thereafter, the workpieces may be required during the first and / or second Heat the cooling phase to the second or third temperature. With cooling in the above-mentioned sense, heating is also necessary understand.

Advantageous refinements of the method according to the invention represent the Objects of the dependent claims.

So it is advantageous to place the workpieces on one for the Carburizing or carbonitriding of common iron materials suitable first Warm temperature between 800 ° C and 1100 ° C. Another advantage is that Workpieces to a second temperature during the first cooling phase between 800 ° C and 950 ° C to cool one for the boronization of the Workpieces to get usable temperature. It is also advantageous that Workpieces to a third temperature during the second cooling phase cool between 800 ° C and 900 ° C to match the material to achieve the appropriate hardening temperature. The workpieces are preferred cooled to room temperature during the quenching phase, so that they are in the Have the connection processed immediately.

A particularly advantageous procedure also results when the first period between 60 min and 360 min and the second period be between 30 min and 360 min. The first and second periods are in Depending on the prevailing temperatures expediently so chosen that a boride layer with a thickness of 10 microns to 100 microns is formed and the edge carbon content directly under the boride layer between 0.6% by weight and 0.9% by weight is an insert depth between 0.2 mm and 2.0 mm.

According to an advantageous development of the method according to the invention, a support by a plasma, that is to say a current-rich glow discharge, takes place during the enrichment phase and / or during the boronization phase. Such a plasma-activated process is described in connection with boronizing, for example by H.-J. Hunger et al. in the article "Plasma-activated gas boronization with boron trifluoride", HTM 52 (1997) 1. The support by a plasma usually takes place at negative pressure and offers the advantage of a lower consumption of carbon or boron donors compared to a purely thermal activation. The gas atmosphere expediently contains boron trichloride (BCl ₃ ) and / or boron trifluoride (BF ₃ ) and / or diborane (B ₂ H ₆ ) during the boronation phase. Above all, the use of boron trifluoride as a boron donor has proven to be advantageous for plasma-activated boriding. This is because, on the one hand, there is no thermal activation during boronization with boron trifluoride, so that the boronization process is limited to the workpieces located in the region of the cathode case and boronization, for example of the inner walls of a boronization chamber, is avoided. On the other hand, boron trifluoride is gaseous even at room temperature, so that an evaporator can be dispensed with economically.

It is also useful if the workpieces during the quenching phase a third pressure, preferably a high pressure of more than 1,013.25 mbar, in a reducing or neutral gas atmosphere or in a liquid Quenching medium are quenched to provide adequate Ensure cooling rate. The hardened in this way Workpieces can then - as is known from case hardening - at a Leave the temperature between 150 ° C and 200 ° C in a separate oven become.

A particularly advantageous procedure is also given when the workpieces consist of a low-carbon iron material, preferably a case hardening steel according to DIN 17 210. In contrast to the prior art, the method according to the invention is not limited to ferrous materials which initially have a relatively high carbon content, such as conventional quenched and tempered steels Ck 45, Ck 60 or 42 CrMo 4. Rather, the method according to the invention makes it possible to use low-carbon Boronize ferrous materials, such as common case-hardened steels Ck 10, C 15 or 20 MoCr 4. The reason for this is that the enrichment phase upstream of the boronation phase enables the surface layer of the workpieces to be enriched with carbon which, after the boronization phase and thus the diffusion phase has ended, leaves a sufficient carbon content in the surface layer with regard to the required carburization.
In a preferred development of the method according to the invention, both the first pressure and the second pressure are between 0.1 mbar and 30 mbar. The pressure depends primarily on the prevailing temperature and the respective composition of the gas atmosphere. For example, during the enrichment phase, the first pressure should be set so that on the one hand a comparatively rapid carburization of the surface layer of the workpieces is achieved and on the other hand a generally undesirable carbide or soot formation on the surface of the workpieces is avoided. The first pressure and the second pressure do not have to be the same and not necessarily constant during the enrichment phase and the boronation phase. Rather, they can be varied, for example pulsed, according to the desired treatment result.

To achieve the above object, moreover, a device for performing the method described above is proposed in accordance with claim 14, comprising at least one treatment chamber, in succession, the heating-up phase, the enrichment phase, the first cooling phase, the boriding, the second cooling phase and Quenching phase are feasible.

In the simplest case, such a device can be a single-chamber vacuum furnace be in which the process steps described above in succession and without Batch transport can be carried out.

A first preferred embodiment of such a device sees two Treatment chamber before, the in the first treatment chamber Heating phase, the enrichment phase, the first cooling phase, the Boronization phase and the second cooling phase are carried out and the quenching phase being carried out in the second treatment chamber. By having a separate treatment chamber for the quenching phase, high-pressure gas quenching can be carried out in a simple manner by means of the relatively high quenching rates can be achieved.

In terms of higher throughput, a second looks preferable Design of the device according to the invention three treatment chambers before, in the first treatment chamber the heating phase and Enrichment phase are carried out, being in the second Treatment chamber the first cooling phase, the boronization phase and the second cooling phase are carried out and being in the third Treatment chamber the quenching phase is carried out.

A third preferred embodiment of the device according to the invention provides four treatment chambers arranged in succession or in parallel, the heating phase being carried out in the first treatment chamber, in the second chamber the enrichment phase or Enrichment phase and the first cooling phase are carried out, wherein in the third treatment chamber the first cooling phase, the Boronization phase and the second cooling phase or the boronization phase and the second cooling phase can be carried out and being in the fourth Treatment chamber the quenching phase is carried out.

A fourth preferred embodiment of the device according to the invention provides six treatment chambers in front, arranged sequentially or in parallel are, the first treatment chamber as a heating chamber for Perform the heating phase, the second treatment chamber as Enrichment chamber for carrying out the enrichment phase, the third Treatment chamber as a cooling chamber for performing the first Cooling phase, the fourth treatment chamber as a boronization chamber Carrying out the boronization phase, the fifth treatment chamber as Cooling chamber for performing the second cooling phase and the sixth treatment chamber as a quenching chamber for carrying out the Quenching phase are formed. By having a separate one for each process step Treatment chamber is present, such is distinguished Heat treatment plant with a particularly high throughput through a comparatively easy to control process management.

Finally, in accordance with claim 19, a workpiece is proposed that consists of a metallic material and the inventive Process is heat-treated, the workpiece with an outer Iron boride layer from 10 microns to 100 microns thick and one under the Iron boride layer, case hardening layer, which has a Vickers hardness between 600 and 900 and a case hardening depth between 0.2 mm and 2.0 mm has, is provided.

Fig. 1

ein den Temperatur- und Druckverlauf des erfindungsgemäßen Verfahrens über der Zeit veranschaulichendes Diagramm;

Fig. 2

eine schematische Darstellung eines Ein-Kammer-Vakuumofens mit Gasabschreckung;

Fig. 3

eine schematische Darstellung eines Zwei-Kammer-Vakuumofens mit Gasabschreckung;

Fig. 4

eine schematische Darstellung eines Zwei-Kammer-Vakuumofens mit Ölabschreckung;

Fig. 5

eine schematische Darstellung einer Wärmebehandlungsanlage mit sechs Behandlungskammern und

Fig. 6

eine schematische Darstellung eines Drei-Kammer-Vakuumofens mit Gasabschreckung und Spülschleuse.

Details and further advantages of the method according to the invention and the corresponding device result from the following description of preferred exemplary embodiments. The accompanying drawings show in detail:

Fig. 1

a diagram illustrating the temperature and pressure profile of the method according to the invention over time;

Fig. 2

a schematic representation of a single-chamber vacuum furnace with gas quenching;

Fig. 3

a schematic representation of a two-chamber vacuum furnace with gas quenching;

Fig. 4

a schematic representation of a two-chamber vacuum furnace with oil quenching;

Fig. 5

a schematic representation of a heat treatment plant with six treatment chambers and

Fig. 6

a schematic representation of a three-chamber vacuum furnace with gas quenching and flushing lock.

In the diagram shown in FIG. 1, the time t and are on the abscissa the temperature ϑ and the pressure p are plotted on the ordinate. That based on Fig. 1 illustrated heat treatment process is a duplex process in the mentioned above and serves for combined carburizing, boronizing and Hardening of workpieces made of a low-carbon iron material, for example case hardening steel C 15 (material number 1.0401). The The entire process can be divided into six phases A to F.

During the first phase, heating phase A, the workpieces to be treated are heated to a first temperature ϑ ₁ of approx. 1000 ° C. The device used for this purpose, for example a heat treatment system according to FIG. 5, is first evacuated after the workpieces have been introduced and then heated to the temperature ϑ ₁ . Alternatively, the workpieces can also be heated to the temperature ϑ ₁ in an inert or reducing gas atmosphere, such as nitrogen (N ₂ ).

After heating to the temperature ϑ ₁ , the workpieces are transported to a second treatment chamber, where during the second phase immediately following the first phase, the enrichment phase B, for a first period of time Δt ₁ , which, depending on the required carburizing depth, between 60 min and 360 minutes, are exposed to a hydrocarbon-containing gas atmosphere. The level of the pressure p ₁ prevailing during the enrichment phase B depends in principle on the desired treatment result and the type of hydrocarbon used and in the present case is approximately 10 mbar. Enrichment phase B can be plasma activated if necessary.

Following the enrichment phase B, the workpieces are conveyed into a third treatment chamber, where they are cooled from the temperature ϑ ₁ to a second temperature ϑ ₂ of approximately 900 ° C. under vacuum during a first cooling phase C immediately following the enrichment phase B. , Alternatively, the workpieces can be cooled to a temperature of ϑ ₂ in a gas atmosphere that mainly contains nitrogen and is therefore inert.

At the end of the cooling phase C, the workpieces are placed in a fourth treatment chamber and borated at a temperature ϑ ₂ and a second pressure p ₂ of approx. 0.1 mbar for a second time period Δt ₂ in a gas atmosphere containing boron. During boriding, the carbon enriched in the boundary layer of the workpieces during the enrichment phase B diffuses into the interior of the workpieces, so that the boronization phase D also represents a diffusion phase for the carburizing process. The time period Δt ₂ for this boronation phase D, which immediately follows the cooling phase C, is between 30 minutes and 360 minutes, depending on the required treatment result. As a boron donating agent, the gas atmosphere contains boron trichloride, boron trifluoride, diborane or several of the aforementioned substances during the boronation phase. If necessary, the boronation phase D can be plasma-activated. In this case, the use of boron trifluoride as a boron donor is particularly suitable.

Immediately after the boronation phase D there is a second cooling phase E, during which the workpieces are cooled in a fifth treatment chamber of the heat treatment system from the temperature ϑ ₂ to a third temperature ϑ ₃ of approx. 800 ° C under vacuum or alternatively in an inert gas atmosphere , To compensate for the temperature within the batch, the workpieces are held at the third temperature ϑ ₃ for about 15 minutes to 30 minutes, as can be seen in FIG. 1.
Finally, the workpieces are quenched from the quenching temperature ϑ ₃ to a temperature of less than 150 ° C., for example room temperature, during a quenching phase F immediately following the second cooling phase E. For this purpose, the workpieces are transported to a sixth treatment chamber and cooled at a high pressure p ₃ of more than 1,013.25 mbar in a reducing or neutral gas atmosphere. Alternatively, the workpieces can also be quenched in a liquid quenching medium.

2 to 6 are different embodiments of a device shown in which the method described above can be carried out. 2 is a single-chamber vacuum furnace 10, in which all process steps A to F in one and the same treatment chamber 11 be performed. The workpieces assembled into a batch 12 are quenched by gas during the quenching phase F.

In contrast, the device shown in Fig. 3 is a two-chamber vacuum furnace 20, which has a first treatment chamber 21 and a second Treatment chamber 22 has. In the first treatment chamber 21 Process steps A to E performed, whereas the as Gas quenching chamber designed second treatment chamber for Quenching the batch 12 serves during the quenching phase F. Of the The device according to FIG. 3 differs from a two-chamber vacuum furnace shown in FIG. 4 30 mainly by the fact that in a second treatment chamber 32, which is separated from the first treatment chamber 31 by a door 33 Oil bath 34 is present, in which the charge 12 during the quenching phase F is deterred. The process steps A to E are analogous to that 3 carried out in the first treatment chamber 31.

5 shows a heat treatment system 40 which is provided with six treatment chambers 41 to 46 arranged in parallel. The treatment chamber 41 serves as a rinsing lock when the charge 12 enters the heat treatment system 40 and as a high-pressure quenching chamber during the quenching phase F at the end of the treatment cycle. The treatment chamber 42 is designed as a heating chamber in which the charge 12 is heated to the first temperature ϑ ₁ during the heating phase A. The charge 12 is carburized in the treatment chamber 43 during the enrichment phase B. The cooling of the charge 12 to the second temperature ϑ ₂ during the first cooling phase C takes place in the treatment chamber 44. The batch 12 is borated during the boronation phase D in the treatment chamber 45, whereas the treatment chamber 46 is provided for cooling and equalizing the batch 12 to the third temperature ϑ ₃ during the second cooling phase E.

A three-chamber vacuum furnace 50 can be seen in FIG. 6. In addition to three treatment chambers 51 to 53 arranged one behind the other, the vacuum oven 50 has a rinsing lock 54, through which the charge 12 is introduced into the vacuum oven 50. The treatment chamber 51 is used for heating to the first temperature ϑ ₁ during the heating-up phase A and for carburizing the charge 12 during the enrichment phase B. In the treatment chamber 52 the cooling to the second temperature ϑ ₂ during the first cooling phase C takes place, the boronization of the charge 12 during the boronation phase D and the cooling and equalization of the charge 12 to the third temperature ϑ ₃ during the second cooling phase E. The treatment chamber 53 is provided for a final gas quenching during the quenching phase F.

The workpieces treated by the method described above have a outer iron boride layer from 10 microns to 100 microns thick and one under the Case hardening layer with iron boride layer and Vickers hardness between 600 and 900 and a case hardening depth between 0.2 mm and 2.0 mm on. They are characterized by a comparatively high fatigue strength and fatigue strength with high wear resistance. The reason for this is that by Process steps A to F obtained combination of carburizing, boronizing and Hardening. So arise from the immediately consecutive Process steps A to F synergy effects that an efficient process management Take into account. Because the process can be done in a single cycle and in perform a single heat treatment plant without interruption, which means significant economic advantages compared to the previous one separate carburizing, cooling, boriding and hardening can be achieved.

LIST OF REFERENCE NUMBERS

10

Single-chamber vacuum furnace

11

treatment chamber

12

charge

20

Two-chamber vacuum furnace

21

treatment chamber

22

treatment chamber

30

Two-chamber vacuum furnace

31

treatment chamber

32

treatment chamber

33

door

34

oil bath

40

Heat treatment plant

41

treatment chamber

42

treatment chamber

43

treatment chamber

44

treatment chamber

45

treatment chamber

46

treatment chamber

50

Three-chamber vacuum furnace

51

treatment chamber

52

treatment chamber

53

treatment chamber

54

flushing sluice

A

heating phase

B

enrichment phase

C

first cooling phase

D

boriding

e

second cooling phase

F

quenching

t

time

Δt ₁

first period

Δt ₂

second period

θ

temperature

ϑ ₁

first temperature

ϑ ₂

second temperature

ϑ ₃

third temperature

p

print

p ₁

first print

p ₂

second print

Claims (19)

Process for the heat treatment of metallic workpieces, in particular for the combined carburizing, boronizing and hardening of ferrous materials, with the following process steps: a) heating the workpieces to a first temperature (ϑ ₁ ) under vacuum or in a neutral or reducing gas atmosphere during a heating phase (A); b) carburizing the workpieces at the first temperature (ϑ ₁ ) and a first pressure (p ₁ ) reached at the end of the heating phase (A) for a first period of time (Δt ₁ ) in a hydrocarbon-containing gas atmosphere during a heating phase immediately following ( A) subsequent enrichment phase (B); c) cooling the workpieces from the first temperature (ϑ ₁ ) to a second temperature (ϑ ₂ ) under vacuum or in a gas atmosphere mainly containing nitrogen during a first cooling phase (C) immediately following the enrichment phase (B); d) Boronizing the workpieces at the second temperature (ϑ ₂ ) and a second pressure (p ₂ ) reached at the end of the first cooling phase (C) for a second time period (Δt ₂ ) in a gas atmosphere containing boron during a period immediately adjacent to the first Cooling phase (C) subsequent boronation phase (D); e) cooling the workpieces from the second temperature (ϑ ₂ ) to a third temperature (ϑ ₃ ) under vacuum or in a gas atmosphere mainly containing nitrogen during a second cooling phase (E) immediately following the boronation phase (D) and f) quenching the workpieces from the third temperature (ϑ ₃ ) to a temperature below 150 ° C during a quenching phase (F) following the second cooling phase (E). Method according to claim 1,
characterized in that the workpieces are heated to a first temperature (ϑ ₁ ) between 800 ° C and 1100 ° C during the heating phase (A). Method according to claim 1 or 2,
characterized in that the workpieces are cooled to a second temperature (ϑ ₂ ) between 800 ° C and 950 ° C during the first cooling phase (C). Method according to one of claims 1 to 3,
characterized in that the workpieces are cooled to a third temperature (ϑ ₃ ) between 800 ° C and 900 ° C during the second cooling phase (D). Method according to one of claims 1 to 4,
characterized in that the workpieces are cooled to room temperature during the quenching phase (F). Method according to one of claims 1 to 5,
characterized by a first time period (Δt ₁ ) between 60 min and 360 min. Method according to one of claims 1 to 6,
characterized by a second time period (Δt ₂ ) between 30 min and 360 min. Method according to one of claims 1 to 7,
characterized by support by a plasma during the enrichment phase (B) and / or during the boriding phase (D). Method according to one of claims 1 to 8,
characterized by a gas atmosphere during the boronation phase (D), which contains boron trichloride and / or boron trifluoride and / or diborane. Method according to one of claims 1 to 9,
characterized in that the workpieces are quenched during the quenching phase (F) at a third pressure (p ₃ ), preferably a high pressure of more than 1013.25 mbar, in a reducing or neutral gas atmosphere or in a liquid quenching medium. Method according to one of claims 1 to 10,
characterized by workpieces made of a low-carbon iron material, preferably a case hardening steel according to DIN 17 210. Method according to one of claims 1 to 11,
characterized by a first pressure (p ₁ ) between 0.1 mbar and 30 mbar. Method according to one of claims 1 to 12,
characterized by a second pressure (p ₂ ) between 0.1 mbar and 30 mbar. Device for carrying out the method according to one of claims 1 to 13,
characterized by at least one treatment chamber in which the heating phase (A), the enrichment phase (B), the first cooling phase (C), the boronization phase (D), the second cooling phase (E) and the quenching phase (F) can be carried out in succession. Device according to claim 14,
characterized by two treatment chambers, the heating phase (A), the enrichment phase (B), the first cooling phase (C), the drilling phase (D) and the second cooling phase (E) being feasible in the first treatment chamber, and wherein in the second treatment chamber Quenching phase (F) is feasible. Device according to claim 14,
characterized by three treatment chambers, the heating phase (A) and the enrichment phase (B) being feasible in the first treatment chamber, the first cooling phase (C), the boronation phase (D) and the second cooling phase (E) being feasible in the second treatment chamber and wherein the quenching phase (F) can be carried out in the third treatment chamber. Device according to claim 14,
characterized by four successively or parallel treatment chambers, the heating phase (A) being feasible in the first treatment chamber, the enrichment phase (B) or the enrichment phase (B) and the first cooling phase (C) being feasible in the second chamber, in in the third treatment chamber, the first cooling phase (C), the boronization phase (D) and the second cooling phase (E) or the boronization phase (D) and the second cooling phase (E) can be carried out and the quenching phase (F) can be carried out in the fourth treatment chamber , Device according to claim 14,
characterized by six successively or parallel arranged treatment chambers, the first treatment chamber as a heating chamber for performing the heating phase (A), the second treatment chamber as an enrichment chamber for carrying out the enrichment phase (B), the third treatment chamber as a cooling chamber for performing the first cooling phase (C), the fourth treatment chamber is designed as a boronization chamber for carrying out the boronation phase (D), the fifth treatment chamber as a cooling chamber for carrying out the second cooling phase (E) and the sixth treatment chamber as a quenching chamber for carrying out the quenching phase (F). Workpiece, which consists of a metallic material and is heat-treated by a method according to one of claims 1 to 13,
characterized by an outer iron boride layer of 10 µm to 100 µm thickness and a case hardening layer lying under the iron boride layer, which has a Vickers hardness between 600 and 900 and a case hardening depth between 0.2 mm and 2.0 mm.

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