DE2317176C3 - Process for the formation of an iron-manganese-carbide layer on the surface of an article based on an iron alloy - Google Patents

Description

"The invention relates to a method of forming a Iron-manganese carbide layer on the surface of a , Article based on an iron alloy Heating the object in a powdery treatment material which contains a manganese-containing metal powder and a halogen-containing carrier, 'thereby improving a mark on the object

* Imparts hardness and wear resistance.

It is known that the iron-manganese-carbide-Schichi,

>; aie formed on the surface of an iron object ; wirc, is very hard and has good wear resistance

(possessed and the formation of iron-manganese-carbide

Layers is on surfaces of metal molds, such as

^ "Patfices and dies, tools such as pincers

and screwdrivers, you need to be angry with all parts

* Zw & k% cler 'Vef e ^^^^^ Ö | p | S

^ Were applied * ^ jS author | n "» for the formation of the

An object made of an iron alloy is that Steaming, spraying, the hardness of the load and the packaging process is known. These conventional processes, however, have a number of components, such as vapor deposition, halogen compounds, for example, are used as a source for the metal to be applied. Therefore, a complicated apparatus such as a special atmosphere furnace is required; and the Hulogen gases quickly erode the apparatus. The metal spraying requires an expensive treatment material and the bonding of the layer formed on the surface of the object is not very good. The charging hair takes a long time to process and the surface of the layer formed is not very smooth. In the conventional wrapping method, the object to be treated must be heated in the non-oxidizing atmosphere or a sealed container containing the object to be treated must be heated.

Therefore, the packing method requires a special atmospheric oven or a special one

zo sealed container.

From the literature reference Minkewitsch (Chemical-thermal surface treatment of steel (lfÖ3). Page 426. Absa '/ ">) it is known to form a dense manganese carbide layer on iron by adding manganese to a temperature of 1100 "C in a gas atmosphere diffuse in from hydrogen and hydrogen chloride leaves. Here / u it is therefore necessary to have a container for placing the halogen gas and hydrogen around the object to be treated, and

Devices for supplying this gas mixture

provide, with the serious disadvantage shows that the used hydrogen chloride

The gas atmosphere is highly corrosive. From US-PS 2 t 02 539 a method is for

J5 Formation of an iron-manganese alloy on a ferrous substrate by heating the substrate in a manganese-containing material using common salt as a halogen source and carrier. It should be noted that in this state The measures described in the technology do not lead to an Eiseri-Manganese-Carbide-Schichi. but only to lead a surface layer made of an iron-Mapgan alloy. The object of the present invention now exists in being easy to use and inexpensive Method of forming an iron-manganese-carbide layer of great density and uniformity on the Surface of an object made of a carbon-containing iron alloy that is exposed to air

i / o and can be carried out at relatively low temperature.

This object is achieved in that the object is ent- holding treatment material heated _Jf object of the invention is therefore a process for tJiiduRg a Eiscn manganese carbide layer AjF the surface of an object based on an iron alloy by heating the article in

(o a powdery! treatment material that contains a manganese-containing metal powder and a halogen-containing carrier, which is characterized by Kp && _t

'' ^^ ίηίηΜ ^^ ψφίβψί'Ψο carbon containsiiirdenii 'Behahdipgsrnaterial heated as a transfer ^

Kaliüm'tetränuobörat, Natrjumtetrafluoborät and / odeiv. Contains ammonium tetrafluoborate _?

\ The invention will in the following description

Miller reference explains the drawings as follows. In the drawings / cigi

Fig. I is a photomicrograph showing a Bison-Man Gun-Ciirbid-Shk'hi on carbon tool chair v: Eigi, which is formed according to Example I,

2 is a photomicrograph showing another layer of ice manganese carbide on carbon tooling formed according to Example 1,
_; F i g. 3 is a photomicrograph showing yet another Fjiscn Manganese Carbidschichi x formed on carbon tool steel according to Example I;

F ί g. 4 a photographic showing the relationship between shows the levels of carbon and manganese contained in the layer formed and the abscess from the surface of the layer,

5 is a photomicrograph showing an iron-manganese-carbide layer formed on the surface of a carbon structural steel according to Example 2;
_H 6 is a photomicrograph manganese Cprbid Eiüen layer is one which is formed on the surface of carbon Werkzeugsiahl according to Example 3,

Figure 7 is a photomicrograph showing an iron-manganese carbide layer shows that formed on the surface of the carbon tool steel according to Example 4 will,

F i g. H a photomicrograph? according to the teaching of US-PS 21 02 539 with NaCI as halogen-containing Transfer formed surface layer.

Fig. 9 is a photomicrograph of the after teaching USPS 2102 539 mil NaF as halogen-containing! Surface layer formed by carrier, and

Fig. 10 is a photomicrograph according to the teaching of US-PS 21 02 539 with NH ₄ CI as halogen-containing! Carrier formed surface layer.

Taken as a whole, the present invention is directed to a new packaging method for forming an iron-manganese-carbide layer on the surface of an object based on an iron alloy containing carbon by introducing manganese the surface of the object and combining this manganese with the carbon and iron that: n the subject matter are directed. The process according to the invention can be carried out in air or in an inert atmosphere Gas atmosphere and are carried out at relatively low treatment temperatures.

It has been found in the implementation of a large number of experiments, that the method of the invention 'on the carbide layer in air without a special container and at a relatively low temperature can form * 700 ⁰ C. This process therefore does not require a special atmospheric furnace or container and is very suitable for the surface treatment of tools, dies and parts for many types of equipment. It is also very productive and it has been found that the carbide seal thus obtained is firmly and tenaciously integrated into the surface of a mother article and that it also has a dense and uniform metallic phase. The Vickers hardness of the layer is around Hv 1400.

To herzusteilen pulverfönrjge the treatment material, a Aikalitetrafluoboratpuiver and the powder of manganese-containing metal yrerden mixed together Ate Alkalitetrafluoborat can be used and Ami oniumtetrafluoborat (NH ₄ BFi) Kaliumtetrafluoborat (KBF _4), Natriurntetrafluoborat ₍₄ NaBF). In the powdery treatment material!

kunn one or more than one ArI from Alverbindteirufluo borot can be used: dici.e Alkaliiotrnfluoborau act as promoters for this powdery ßehandlungsmaierinl,

Metallic manganese and manganese alloys can be used as the metal containing manganese and as the main component of the light treatment oniatric works. The alloys are alloys with iron. The alloys with iron are particularly suitable for

Jo the metal of the trading material, because tlie alloys are cheap and easy to obtain ^r ; iiid. It is preferred that the alkali tetrafluoborate is selected from one which passes through a sieve with a mesh size of 0.148 mm or less and that the metal powder passes through a sieve with a mesh size of 0.42 mm or less. The powdery alkali tetrafluoborate can be contained in the treatment maierial in an amount of 1 to 40 wt be uniform. Too much alkali tetrafluobonii would cause the processing material to merge and sinter with a high treatment temperature. The treatment material is therefore allowed to solidify after the treatment process, which is difficult. to remove the treated object from the Betiandlungsmatcrial and the treatment material repeatedly becomes unusable and also the surface condition de. Item are not good. The amount of alkali tetrafluoborate is preferably between 2 and 30% by weight. The remainder of the material is the powdered metal mentioned above. The powdery metal can be mixed in an amount of 60 to 99% by weight, and preferably in an amount of 70 to 98%. To prevent the treatment material from solidifying, an inactive powdery substance with a high melting point, such as aluminum oxide (Al2O3), silicon dioxide (SiO ₂ ), boron nitride (DN) and / or chromium oxide (Cr ₂ O ₃ ), can make up to 80% of the treatment material be admitted.
The heating temperature may vary over a wide range from 650 to 1200 ^0C. At a heating temperature below 650 ° C, the suitably thick carbide layer cannot be formed on the surface of the treated object and in the case that a temperature above 1200 ° C

is so chosen, the powdery treatment material would be made to sinter and the treated The object would bond with the treatment material. This would reduce the property of the Object based on the iron alloy deteriorates

SS tert. The preferred range of the heating temperature is 700 to! 000 ⁰ C.

If objects based on the iron alloy are treated at a heating temperature above the ot * = sy transformation point of the iron-based alloy in order to bind the carbide more quickly, deformation can occur in most objects as a result of the transformation of the iron-based alloys. The deformation can, of course, by lowering the heating temperature below 800 ⁰ C for alloy steel and avoided below 70o ⁰ C for carbon steel. The present invention can be carried out at a lower temperature, for example lead-650 ⁰ C.

23 17 J 76

The iron-manganese-carbide layer can therefore be used without Deformation can be formed.

The heating line depends on the strength of the carbad to be formed. Less than 1 hour heating however, cannot provide a practically acceptable formation of the layer, albeit the ultimate! the heating time depends on the heating temperature. As the heating time increases, the Increase the strength of the carbidschichl accordingly. An acceptable thickness of the layer can be within 30 Hours or less can be practically realized. The preferred range of heating time is between 2 up to 10 hours.

The iron alloy-based article must contain at least 0.1% by weight of carbon. the Carbon in the object turns into a carbide mixture during the treatment, namely Hs becomes suspects that the carbon in the object penetrates to its surface and with the manganese out of the Treatment material reacts to form the carbide on the surface of the article. The higher one Content of carbon in the article is more preferred for the formation of the carbide layer. The subject on Base of the iron alloy, which contains less than 0.1 wt .-% carbon, can not with a uniform and strong carbide are formed by the treatment. As long as the items are based on the Iron alloy contain at least 0.1 wt .-% carbon, any kind of iron alloys, such as Iron alloys with chrome. Tungsten. Molybdenum or nickel, for the subject matter of the present invention be used. A pure iron article with 0.1 wt% or more carbon in the part near the surface, to which carbon has been added from the outside by means of hardening, can also be used as Subject of the present invention can be used.

Ia Ki not necessary to the procedure of the present Invention to be carried out in a water-casting atmosphere or in a non-oxidizing gas atmosphere, but the process can be carried out effectively either under an air atmosphere or in an inert gas atmosphere will.

The following examples illustrate the invention. In the examples, small rods used as samples were regarded as models of mandrels of the molds and rod-like parts of various devices.

example 1

Various types of powdery chanding materials which contain 60 to 48% by weight of ice-manganese alloy (with 76% manganese) and pass through a sieve with a mesh size of up to 0.148 mm, with the remainder being KBF ₄ , which passes through a sieve with a mesh size of up to 0.074 mm, are each placed in aluminum oxide crucibles with an inner diameter of 45 mm and a height of 60 mm, and then samples of carbon tool steel with a diameter of 10 mm and an I lohe made of 5 mm (JIS SK4 mn 1.0 Gcw .-% carbon) in each of the ßchandlungsinaierialien in the crucible and packed in an electric furnace for 4 hours at l.ufliitmospharc cmc temperature of 700 to 900 'C ^- heated. They are then removed from the furnace and placed on the l.ufi iih - {! Ckiilill. (Before treatment, the samples were treated to remove rust and rinsed to expose the metallic surface.) During the heating process, the crucibles? not covered with a lid. All samples are cut up and their cross-section examined with a microscope. Some of the samples are also examined with the X-ray diffraction method and / or the microprobe.

The photomicrograph shown in Fig. 1 was taken from a sample 'containing 20% KBF4 and 80% iron-manganese Legicrung,' 4 hours at 700 ⁰ C in the powdery Bchandlungsmaterial treated. Also, the photomicrographs shown in Fig.2 were made from samples that show at 800 "C in the Bchandlungsmatenal containing 2% KBF4 or were treated at 900 ⁰ C in the treatment material containing 30% KBF4. The microphotographs that an excellent layer is obtained on the surface of each of the samples The other samples treated in this example were also observed to have an excellent (integrated and dense) layer similar to those shown in Figs Layers is.

Upon microscopic examination, it was found that the thickness of the formed layer is constant _{within the range of 2 to 40% by weight of KBF 4.} However, the strength is greatly influenced by the heating temperature.

The strength increases as the heating temperature rises. The examinations with the microprobe show that the layers formed in large quantities Contain manganese and carbon. For example, one of the results of such an investigation is in F i g. 4 with the ratio of the contents of manganese and carbon. which are revealed in the formed layer.

and the distance from the surface. The test layer is applied to carbon tool steel at 900 C in the treatment paint. containing 30 wt .-% KBf _{4 is} formed. In FIG. 4, the ordinate and the abscissa represent the contents (% by weight) of manganese and carbon or the distance or the depth (in μm) from the surface of the sample. In the range up to 2 or 3 μm from the surface, about 12% by weight of manganese are contained and when the distance increases, the content of manganese decreases quickly and the content becomes about 0 at a distance of 13 to 14 μm. On the other hand, the content of carbon near the surface is 4.5 to 4.7% by weight. at a distance of 4 to 6 μm about i "/ t> and at a distance of 8 μm the content of carbon is 1% by weight, which is equal to the carbon content of the mother steel.

The above-mentioned layer examined with the microprobe was also examined with the X-ray diffraction method examined and it was found that the layer consists of iron-manganese carbide. Also the upper part of the multicrial contains manganese in the form the solid solution of manganese in iron. A second coat was used on some treated samples observed between the ice-manganese-carbide layer and the mother material. The second shift was made recognized as a solid solution of iron.

According to the example described above, it is clear that the manganese of ßehandlungsmatcrials in the surface of objects made of carbon composite material penetrates and using a powder feed

(, <, some working material which in a wide range reveals KBF ^, and forms ice-manganese carbide with the carbon and iron contained in the object.

te * · ■ *.

Example 2

I samples of 10 mm diameter and 5 mm height -y faus construction carbon steel (JIS S IOC with 0.1 wt ° / o -. 'Carbon) were prepared and from which the grate was -Removes be analog Example 1 treated.

Ä ^ lfe treated specimens are examined with a microscope

watched and some of them are using the

«X-ray diffraction method and / or ^{examined with the T} microprobe. On microscopic [Observation shows that all the treated samples £ _(are coated with a thin layer. The four hours

ibei contains 800 ⁰ C treated layer in the powdery j ,, treating material containing 2% KBF _4, is shown as an example in Fig.5. From the results of the examination with X-ray diffraction and the

(Microprobe the layer is recognized as iron-manganese-carbide i, JFe, MnJsC, whereby the upper part of the : -i mother material contains a solid solution of iron and manganese.

20th

Example 3

NaBF ₄ , which passes through a sieve with a mesh size of 0.074 mm or less, is used as a promoter in place of KBF ₄ in the treatment materials used in Example 1. Samples 10 mm in diameter and 5 mm in height made of carbon tool steel (JIS SK3, C: 1.00- 1.10 wt.%. Si: less than 0.35 wt.%, Ni: less than 0.50 % By weight, P: less than 0.030% by weight, S: less than 0.030% by weight, remainder iron) are treated analogously to Example 1 with the exception of the promoters mentioned above. All treated samples are examined microscopically and some of them are examined with X-ray diffraction and / or the microprobe. The microscopic observation shows that all treated samples are coated with a layer. As an example, the photomicrograph made of the sample treated at 800 ° C. for 4 hours in the treatment material, which contains 10% by weight NaBF ₄ , is shown in FIG. 6 and the layer is represented as iron-manganese carbide (Fe, Mn ) ₃ C recognized.

According to the example it is clear that NaBF ₄ acts as a crown in this treatment material.

Example 4

NH ₄ BF ₄ , which passes through a sieve with a mesh size of 0.074 mm or less, is used as a promoter of the KBF ₄ in the treatment materials used in Example 1. The samples, which were made from carbon tool steel, which is the same as the steel used in Example 1, are for 4 hours at temperatures of 700 to 900 ° C in the powdery treatment material containing 30 wt .-% NH ₄ BF ₄ , treated. All treated samples are observed with a microscope and some of them are examined with X-ray diffraction and / or the microprobe. Microscopic observation shows that all treated samples are coated with a layer. The microphotograph made of the sample treated at 700 ^{° C. is shown in FIG.} 7 shown as an example. This layer is also recognized as iron-manganese carbide (Fe, Mn) 3C.

Comparative example

To prove the fact that after the measures described in US Pat. No. 21 02 539 the formation of an iron-manganese-carbide layer is not possible, a comparison test is carried out in which a powdery treatment material with a particle size of less than 0.149 mm containing 95% of an iron-manganese alloy and 5% sodium chloride or sodium fluoride or ammonium chloride, placed in an aluminum oxide crucible. Then, samples of carbon tool steel (JIS SK4) containing 1.0% carbon are packed in the treatment material and heated ^{in the uncovered crucible in an electric furnace at 950 ° C. for 5 hours in the normal atmosphere.} The samples are then removed from the oven and allowed to air cool.

The results obtained are shown in the accompanying Figs. 8, 9 and 10 on the basis of photomicrographs that reproduce the microstructure of the treated samples, clarified. So it can be seen that with all Samples on the surface do not have an iron-manganese-carbide layer, but a thin layer of one solid iron-manganese solution is formed.

For this purpose 3 sheets of drawings 709 628/202

Claims (6)

23 Π 176 claims: 1. Process for the formation of a ^ iron-mangiin-rarbicl-layer on the surface A. "of an article based on an iron alloy '% IBy heating the article in a powder * formigen Behandlungsmaierial, a manganese day ·, containing Melallpulvcr and a halogen-containing carrier contains, characterized in that an object based on an iron alloy containing at least 0.1 wt ° man / o Contains carbon, heated in the Bchandlungsmaterial, which contains potassium tetrafluoborate, sodium (etrafluoborate and / or ammonium tetrafluoborate as a carrier). 2. The method according to claim I, characterized in that the article I to 30 hours ., ".. a temperature of 650 ⁰ C to I200 ° C in the '' -.-. powder treatment material is heated, that essentially consists of I to 40% by weight \ _A iKaliurntetrafluoboriit, Natriumteirafluoborat ■ j-yairscV or ammonium tetrafluoborate and 60 to 99 '"Consists of wt .-% metal. 3. The method according to claim 1, characterized in that the object on the basis of a Iron alloy containing at least 0.1% by weight of carbon from iron containing carbon, Carbon steel or a carbon-containing steel alloy. 4. The method according to claim 1, characterized in that the object before heating to Increase in the carbon content in the part near the surface is case-hardened. 5. The method according to claim 1, characterized in that there is used as a manganese-containing metal powder a powder of metallic manganese, an alloy or an iron-manganese alloy is used, which passes through a sieve with a mesh size of 0.42 mm. 6. The method according to claim I. characterized in that the powdery treatment material is aluminum oxide and / or boron nitride and / or chromium oxide and / or silicon dioxide as inactive pulverulent subs' additive.