DE2456530A1 - OVERHARD MARTENSITE AND METHOD FOR ITS MANUFACTURING - Google Patents

Description

720 Gonzales Röad

Santa fe, lew mexico 85701

Our sign; E 823

Superhard martensite and its method of manufacture

The invention relates to an overhard (super hard) Martensite, in particular a steel hardened by ion implantation, and a method for its production.

There are already various methods of coating the Surface of a substrate with a material known, such as. Such as that described in U.S. Patent Application No. 279,244 Ion deposition. A device for implementation this ion plating, which is described in more detail below, is from the article by T.Spalvins et al, "Deposition of Thin Films by Ion Plating on Surfaces Having Various Configurations "in" NASA Technical Note D-2707 ", November 1966.

A steel substrate has a cubic, internally centered grid. When the substrate is heated, the configuration changes in a face-centered cubic lattice (austenite), the

Dr. Hn / de

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after quenching, a tetragonal inner-centered one Lattice forms. The tetragonal shape is martensite.

By nucleation and / or inhibition of martensite grain growth A very fine grain can be obtained in the hardening process. The finer the grain in the martensite the harder the steel is. At the same time, embedded insoluble atoms act as barriers for the movement of the Dislocations (dislocations) that lead to further improvement contribute to hardness and strength.

According to the invention, the martensite grain growth is now inhibited by implantation (incorporation) of ions of any Element that is insoluble in iron in the substrate (the steel matrix) in a sufficient amount. About these elements include helium, neon, argon, krypton, xenon, radon, lithium, sodium, potassium, rubidium, cesium, frankium, calcium, Strontium, barium, radium, silver, cadmium, mercury, thallium, lead and bismuth. In the invention In the process, the following additional elements can be used as they all have pronounced low solubility in iron or have limited solubility: beryllium, magnesium, yttrium, lanthanum, zirconium, Hafnium, thorium, tantalum, copper, indium, selenium, tellurium and polonium. This procedure gives you an exceptional one hard martensite, which is used for the production of excellent cutting tools with wear-resistant Surfaces suitable j it can also be used in gear wheels., Ball bearings, Measuring tools and the like. Be used. The f.-a

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granular martensite gives feathers, hammers and the like. Also improved resistance to fatigue and improved impact strength.

It has now been found that the inventive method The best results are obtained when using a normalized or a soft annealed (annealed) steel, i. H. a steel with a low hardness is used. The preferred substrate for use in the present invention should be a steel that has enough interstitial alloy atoms has to be "curable", which is usually a Alloy content within the range of 0.3 to 1.8 wt.% Has, with the optimal alloy range at 0.5 to 1.0% by weight. With these interstitial alloy atoms, are those from the second period of the Periodic Table of the Elements and they are selected from the group consisting of beryllium, boron, carbon and nitrogen. Those present in the steel substrate Substitution alloy elements are generally of no importance to the present invention.

It has now been found that an element which is insoluble in iron can be implanted (inserted) into a steel substrate the growth is delayed and / or during the martensite formation nuclei in the grain, whereby a more uniform and fine-grained martensite structure is formed, which leads to a harder substrate.

When treating a hardenable steel substrate or material (with, for example, 0.6% carbon) after the

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inventive method should first surface of the steel must be cleaned. This is accomplished using any conventional cleaning technique. That The substrate is then inserted into a vacuum chamber supported on a suitable support and an insulating metal plate is arranged to form a cathode to which a terminal of a high-voltage direct current source is connected. Larger objects can be applied to insulators and directly to the negative Pole of the direct current source are connected. The other terminal of the DC power supply connects to a connected to a suitable anode, which may be the electrically conductive metal floor of the chamber. More often, the substrate is placed on the bottom of the chamber and the anode is attached to it, around the chamber easier to charge and discharge. The chamber

-5 is then applied to a pressure of about 1 × 10 mm Hg evacuated. It is cycled with argon or some other inert gas that is used or implanted into the substrate is to be flushed and evacuated, the whole being carried out two or three times.

The argon or another gas is then slowly introduced into the chamber while simultaneously between the substrate or a voltage is applied to the object and anode. At a vacuum of about 2 χ 10 mm Hg begins a pink plasma will form at around 600 to 800 volts. The voltage is then set to the desired value increased, for example 4.5 KV. The object (the substrate)

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is then for a certain period of time (2 to 4 minutes) bombarded with this argon or inert gas plasma. Then it is allowed to cool inside the chamber to a Prevent oxidation. In addition, when a fine solid is deposited by ion plating to produce a wear-resistant, corrosion-resistant coating or some other coating, the other terminal is connected to a tungsten wire anode which is then subjected to resistance heating to melt the coating material. An electron centrifugal evaporator, a spray evaporator or any other source of steam can be used.

The article or substrate Xtf is then up to heated to the austenite temperature range and, depending on the alloy content in "water, oil or air, to the martensite temperature range deterred. The treated surface layer can also by ion bombardment down to the Austenitic temperature range and heated by a backing substrate material, such as. B. a cooling plate or by cooled contact holders, are quenched. Helium, argon or anything else can also be used for quenching Gas can be introduced into the vacuum chamber.

The voltage applied to the system can range from 200 to 20 Volts or more vary. Ion accelerators with voltages up to 2,000,000 Volts are used. A voltage of 4 KV applied for a few minutes was found to cause penetration of argon ions into the substrate to about 20 microns

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leads. The implantation concentration 'sounds when applied from 4 KV to 20 microns. The speed of the hitting Ions determine the depth of penetration. The higher the applied voltage and the lower the gas pressure, the more the ions move faster when they hit the substrate. The distribution of the insoluble implanted Atoms is controlled by the hardness of the substrate and the course of the tension and pressure that occurs during the implantation time be applied. In some cases, the plasma can be better sustained and working conditions can be extended to pressures and / or tensions «which otherwise cannot be applied when a Magnetic field, a high frequency or a radio frequency or a radiation acts on the plasma., Whereby a further Ionization of the gas beyond that produced by the static DC bias voltage will. Such methods are often used to increase ionization in plasmas.

In principle, any element can be used according to the invention, which is insoluble in iron, and these include the inert gases helium, neon, argon, krypton, xenon, radon, the alkali metals Lithium, sodium, potassium, rubidium, cesium, frankium, the alkaline earth metals calcium, strontium, barium, radium. as well as the other insoluble metals silver, cadmium, mercury, thallium, lead and bismuth. Also can Ions of the elements listed below are effectively incorporated (implanted) into a steel substrate because they a pronounced low or limited solubility in iron

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contain: beryllium (0.1 wt.%), magnesium (0.1 wt.%), Yttrium (little), lanthanum (0.1% by weight), zirconium (little), hafnium (little), thorium (little), tantalum (little), copper (little), indium (little), selenium (little), tellurium (little) and polonium (little). "

Although in this implantation procedure all of the above Elements that can be used are preferably used as elements that have an atomic size which is comparable to that of iron. this is best illustrated by examining the effectiveness of the inert gases in the method of the invention. If you have the If these gases are enumerated down in the Periodic Table of the Elements, it should be noted that Helium is the one with the second - lowest effectiveness, that neon is more effective, that argon is the most effective, that krypton is comparable to neon and xenon the least is effective. Argon is the most effective because its aetone size is about the same as that of iron, Xenon and neon have atomic sizes that are too large or too small compared to iron. . .

The method according to the invention can also be carried out by simultaneous or successive bombardment of the substrate with one of the selected implantation elements and one of the selected interstitial alloying elements followed by hardening. This procedure delivers the same result, namely an overhard (super hard) Martensite. The present invention can also be carried out by bombing a mild steel (mild steel) with insoluble ions

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245B530

and carbonizing (carburizing) the steel by any of the conventional methods either before or after ion bombardment be carried out to produce a core-hardened product with an over-hard surface.

The following table I explains the process according to the invention. The steel substrates specified therein have been with various elements for a selected period of time implanted at different voltages and then hardened. Then the hardness of the product obtained was determined. Knoop hardness indentations (depressions) were produced with a load of 100 g and at twenty times magnification measured.

Table I.

Element Spf ^ opening Time
(Minutes) Knoop hardness untreated
tes substrate argon 4.5 3 830 It 4.5 7th 1,080 It 2.5 5 1,000-1,030 xenon 4.5 5 910 dd 4.5 10 1,000 helium 2.5 5 1,000 helium 2.5 2
(+ 3-minute
Silver ion
• plating) 890-910

silver

3.0

960

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The following Table II illustrates the Knoop hardness obtained was when iron-soluble elements (iron and titanium) in a steel substrate for a predetermined period of time were stored (implanted) and then the whole thing was hardened:

Tabel II Knoop hardness element Voltage (KV) Time (minutes) 810
840
790-810 iron
titanium
Helium + 3.0
3.0
Iron He 2.5
Fe 2.5 3
3
2
3

In the examples in Table I, the steel substrates used contained 0.95% by weight carbon and the remainder iron. . Each substrate was approximately 2 inches by 5/8 inches by 1/32 inches in size. A chamber similar to that described in the above article (NASA technical note D-27O7) was used, which was first flushed several times with the gas to be used and then evacuated to a vacuum at which the plasma could be maintained, namely to a those near 5 10 " ⁵ (2 - 50 χ 10" ⁵ ) mm of mercury.

When implanting (storing) silver ions in the steel, a tungsten wire was used as the anode and around the WoI frame wire a silver wire was wound. The tungsten wire was then resistively heated in the vacuum chamber

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subjected to melt the silver so that it could evaporate onto the substrate. This procedure was also applied to the metals in Table II which were used in place of the silver wire.

In the curing step, each substrate was stored in Oe) or bombarded with ions in after implantation the chamber heated to about 850 to about 1050, preferably to about 1000 C, so that it is within the γ-austenite range and then quenched in water to around room temperature to form martensite. After that, the Surface of each sample substrate using a 2% nital solution (solution of nitric acid in ethanol) etched. Instead of the usual needle-shaped structure of martensite, which had crystals in the untreated sample, whose main length (length in the main axis) at 6,700 times magnification was about 40 mm, the treated substrates have a very fine-grain martensite structure whose grains were no longer than 6 mm. Because the volume and weight of the grains a third of their Length or its diameter, the treated

3 3
Delte structure 40/6 = daä3O5-fold de:

and .50 times the grain boundary area.

3 3
Delte structure 40/6 = da3O5 times the number of grains

Patent claims:

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Claims (18)

Claims 1. Process for the production of an overhard, iron .containing Substrate, characterized in that ions of elements which are insoluble in iron are implanted into the substrate (incorporated), and the substrate is then heat treated to form a hardened martensite structure. 2. The method "according to claim 1, characterized in that the substrate contains an interstitial alloy element selected from the group consisting of beryllium, boron, carbon and nitrogen. 3. The method according to claim 1, characterized in that the substrate after ion bombardment with an element from the group consisting of beryllium, boron, carbon and nitrogen is alloyed. · 4. The method according to claim 2, characterized in that the interstitial alloy element content of the substrate is within the range of 0.3 to 1.8 wt%. 5. The method according to claim 4, characterized in that the amount of interstitial alloying element in the Steel substrate is within the range of 0.5 to 1.0 wt%. 6. The method according to claim 1, characterized in that the implanted (built-in) element from the group of helium, neon, argon, krypton, xenon, radon, lithium, sodium, potassium, 509825/0927 Rubidium, cesium, frankium, calcium, strontium, barium, radium, silver, cadmium, mercury, thallium, lead, bismuth, beryllium, magnesium, yttrium, lanthanum, zirconium, Hafnium, Thorium, Tantalum, Copper, Indium, Selenium, Tellurium and Polonium is selected. 7. The method according to claim 1, characterized in that that the substrate is an alloy steel - '- is. 8. The method according to claim 1, characterized in that that the implanted element has an atomic size substantially the same as that of iron. 9. The method according to Angruch 8, characterized in that the implanted element is argon. 10. The method according to claim 8, characterized in that it is silver in the implanted element. 11. Substrate, characterized in that it is according to the method one of claims 1 to 10 has been treated to produce a superhard martensite. 12. The method according to claim 1, characterized in that in the iron implantation step the substrate in a A vacuum is introduced, an inert gas is introduced into the vacuum, an electrical through the inert gas with the substrate as the cathode Plasma discharge creates and the voltage (the potential) 509825/0 927 held in vacuum within such a range at which the plasma is maintained. 13. The method according to claim 12, characterized in that that from the anode or an electrically neutral source something insoluble in iron or only sparingly soluble in iron Metal is evaporated. 14. Upper hard torture, "marked by a Steel substrate, the surface of which is an iron-insoluble, Contains element embedded in the iron, the surface having a fine-grain martensite structure having. 15. Superhard martensite according to claim 14, characterized in that that the element helium, neon, argon, krypton, xenon, radon, lithium, sodium, potassium, rubidium, Cesium, frankium, calcium, strontium, barium, radium, silver, Cadmium, mercury, thallium, lead, bismuth, beryllium, yttrium, lanthanum, zirconium, hafnium, thorium, tantalum, Contains copper, indium, selenium, tellurium or polonium. 16. Super hard martensite, characterized in that its surface has a Knoop hardness of more than 1000, shows. 17. Superhard martensite, characterized by a steel substrate, the surface of which contains an iron-insoluble element embedded in the iron, the surface has a grain size in the longest dimension 509825/0927 - 14 is less than 0.001 mm after normal quenching. 18. 'The method according to claim 1, characterized in that that the plasma by a magnetic field, by radio frequency or radio frequency or by radiation in addition to the lonization produced by the static DC bias is ionized. 509825/0927