METHOD FOR PRODUCING A COMPONENT FROM A METAL ALLOY WITH AN AMORPHOUS PHASE

Abstract

The invention relates to a method for producing a component from an at least partially amorphous metal alloy, comprising the following steps: providing a powder from an at least partially amorphous metal alloy; producing a shaped semi-finished product from the powder in that the powder is applied in layers and the powder particles of each newly applied layer, at least at the surface of the semi-finished product to be shaped, are fused and/or melted by targeted local heat input and bond to one another as they cool again; and hot pressing the semi-finished product, wherein the hot pressing is performed at a temperature that is between the transformation temperature and the crystallisation temperature of the amorphous phase of the metal alloy, wherein a mechanical pressure is exerted onto the semi-finished product during the hot pressing and the semi-finished product is compacted during the hot pressing.

The invention also relates to a component produced by such a method from a powder formed from an at least partially amorphous metal alloy and to the use of such a component as a gearwheel, friction wheel, wear-resistant component, housing, watch case, part of a gear unit, or semi-finished product.

Claims

1. A method for producing a component from an at least partially amorphous metal alloy, comprising the following steps: providing a powder from an at least partially amorphous metal alloy, wherein the powder consists of spherical powder particles; producing a shaped semi-finished product from the powder in that the powder is applied in layers and the powder particles of each newly applied layer, at least at the surface of the semi-finished product to be shaped, are fused and/or melted by targeted local heat input and bond to one another as they cool again; and hot pressing the semi-finished product, wherein the hot pressing is performed at a temperature that is between the transformation temperature and the crystallisation temperature of the amorphous phase of the metal alloy, wherein a mechanical pressure is exerted onto the semi-finished product during the hot pressing and the semi-finished product is compacted during the hot pressing.

2. The method according to claim 1, wherein: the hot pressing of the semi-finished product is carried out by a hot isostatic pressing of the semi-finished product, and the semi-finished product is compacted by hot isostatic pressing.

3. The method according to claim 1, wherein: the hot pressing is performed under vacuum.

4. The method according to claim 1, wherein: the shaped semi-finished product is produced from the powder using an additive manufacturing method.

5. The method according to claim 1, wherein: the targeted local heat input into the powder particles of each newly applied layer is performed using an electron beam or a laser beam.

6. The method according to claim 1, wherein: the powder particles of each newly applied layer in at least 90% of the area of the component to be produced are fused by targeted local heat input in the newly applied layer.

7. The method according to claim 1, wherein: the powder particles have a diameter smaller than 125 m.

8. The method according to claim 1, wherein: the duration of the hot pressing is selected in such a way that the powder particles are bonded to one another after the hot pressing and the produced component has an amorphous content of at least 85 percent.

9. The method according to claim 1, wherein: a powder formed from an amorphous metal alloy containing at least 50 percent by weight zirconium is used as powder.

10. The method according to claim 1, wherein: a powder formed from an amorphous metal alloy comprising a) 58 to 77 percent by weight zirconium, b) 0 to 3 percent by weight hafnium, c) 20 to 30 percent by weight copper, d) 2 to 6 percent by weight aluminium, and e) 1 to 3 percent by weight niobium is provided as powder.

11. The method according to claim 1, wherein: the powder is produced by atomizing, in a noble gas of purity 99.99% or a higher purity.

12. The method according to claim 1, wherein: the powder comprises less than 1 percent by weight of particles with a diameter smaller than 5 m or the powder is screened or treated by air classification, such that it comprises less than 1 percent by weight of particles with a diameter smaller than 5 m.

13. The method according to claim 1, wherein: the hot pressing of the powder is performed at a temperature (T) between the transformation temperature (T.sub.T) and a maximum temperature, wherein the maximum temperature lies above the transformation temperature (T.sub.T) by 30% of the temperature difference between the transformation temperature (T.sub.T) and the crystallisation temperature (T.sub.K) of the amorphous phase of the metallic alloy.

14. The method according to claim 1, wherein: the duration of the hot pressing is selected depending on the geometric shape, of the semi-finished product, and.

15. The method according to claim 1, wherein: the duration of the hot pressing lies in a time range of 3 seconds per millimetre of the thickness or of the greatest relevant diameter of the semi-finished product to 900 seconds per millimetre of the thickness or of the greatest relevant diameter of the semi-finished product.

16. The method according to claim 1, wherein: the powder particles are plastically deformed by the hot pressing.

17. The method according to claim 1, wherein: the powder particles in an inner part of a newly applied layer are not or are only partly fused and/or melted.

18. A component produced by a method according to claim 1, from a powder formed from an at least partially amorphous metal alloy.

19. (canceled)

Description

[0091] Further exemplary embodiments of the invention will be explained hereinafter on the basis of a schematically illustrated flow diagram and on the basis of 3 figures, but without limiting the invention hereto. In the figures:

[0092] FIG. 1: shows and enlarged recorded image of a sintered powder melted using an electron beam and formed from an amorphous metal alloy with 50 times magnification;

[0093] FIG. 2: shows an enlarged recorded image of a sintered powder melted using an electron beam and formed from an amorphous metal alloy with 200 times magnification; and

[0094] FIG. 3: shows multiple X-ray/powder diffractograms of an amorphous ZrAlCuNb powder (lower curve) and amorphous ZrAlCuNb powders, which were sintered at different temperatures.

[0095] In the flow diagram, T denotes the working temperature, T.sub.T denotes the transformation temperature of the amorphous metal alloy, and T.sub.K denotes the crystallisation temperature of the amorphous phase of the metal alloy.

[0096] An amorphous metallic powder is produced from a metallic alloy of which the composition is suitable for forming an amorphous phase or which already consists of the amorphous phase. Powder fractionation is then performed, in which case excessively small and excessively large powder particles are removed, in particular by screening. The powder is then processed by an additive manufacturing method to form a component of the desired geometry. The powder, which forms the external contour of the component, is completely melted and forms a tight, pore-free structure, whereas the powder in the volume of the component is merely sintered, in order to attain an adhesion of the powder particles to the closest neighbour.

[0097] The temperature treatment during the pressing or after the pressing is performed for a period of time of at most 10 min at a temperature above the transformation temperature T.sub.T and below the crystallisation temperature T.sub.K of the amorphous phase of the used metallic alloy.

[0098] Specific practical examples will now follow, in which methods according to the invention are described and in which the results thus obtained are evaluated.

EXAMPLE 1

[0099] An alloy formed from 70.6 percent by weight of zirconium (Haines&Maassen Metallhandelsgesellschaft mbH Bonn, Zr-201 zirconium Crystalbar), 23.9 percent by weight copper (Alpha Aesar GmbH & Co KG Karlsruhe, Copper plate, Oxygen free, High Conductivity (OFCH) product number 45210), 3.7 percent by weight aluminium (Alpha Aesar GmbH & Co KG Karlsruhe, Aluminium Ingot 99.999% product number 10571) and 1.8 percent by weight niobium (Alpha Aesar GmbH & Co KG Karlsruhe, niobium film 99.97% product number 00238) was melted in an induction melting facility (VSG, inductively heated vacuum, melting and casting facility, Nrmont, Freiberg) under 800 mbar argon (Argon 6.0, Linde AG, Pullach) and poured into a water-cooled copper mould. A fine powder was produced from the alloy thus produced using a method as is known for example from WO 99/30858 A1 in a Nanoval atomizing apparatus (Nanoval GmbH & Co. KG, Berlin) by atomization of the melt with argon.

[0100] By separation by means of air classification using a Condux Ultra-Fine Classifier CFS (Netsch-Feinmahltechnik GmbH Selb Germany), the fine grain was separated, such that less than 0.1% of the particles were smaller than 5 m, i.e. at least 99.9% of the particles had a cross section or a dimensioning of 5 m or more, and all powder particles larger than 125 m were removed by screening by means of an analysis screen with 125 m mesh width (Retsch GmbH, Haan-Germany, product number 60.131.000125). The powder thus produced was examined by means of X-ray diffractometry and had an amorphous content of greater than 95%.

[0101] The powder thus produced was applied in layers in an EBM (electron beam melting) manufacturing facility (Arcam AB A1, Mndal, Sweden) without prior heating of the powder, wherein an electron beam with a power from 150 W to 210 W scanned the contour of the component and melted the powder particles. The individual layers thus solidified so quickly that crystallisation was suppressed and the alloy solidifies amorphously. For the sintering of the powder in the volume of the component, the electron beam was fanned out to 50 beams and directed in a planar manner over the powder bed. The energy was thus low enough that the individual powder particles did not melt, but adhered only to their closest neighbour. Recorded images of the powder sintered in this way taken using a microscope are shown in FIGS. 1 and 2.

[0102] During the entire process the temperature of the powder bed must be kept below the crystallisation temperature T.sub.K of the alloy.

[0103] FIG. 3 shows X-ray/powder diffractograms of the starting powder and of powders that have been sintered at different temperatures.

[0104] The starting powder (lower curve) demonstrates no reflexes of crystalline phases, i.e. is completely amorphous.

[0105] At temperatures of 360 C., 380 C. and 400 C., only a few signs of crystallites were found, however these are not tolerable for the processability within the scope of the present invention. From a sintering temperature of 420 C., clear reflexes were visible, indicating a crystalline phase. The crystallisation temperature T.sub.K was exceeded in this case and the sample crystallised out or crystallised too severely.

[0106] The components produced as described were then compacted by hot isostatic pressing at a pressure of 200 megapascal (200 MPa) under highly pure argon (Argon 6.0, Linde AG, Pullach) at a temperature of 400 C. for 300 seconds. The powder in the volume of the component was thus also completely compacted and forms a compact, pore-free body.

[0107] Fifteen components produced in this way were examined by means of metallographic microsection with regard to the amorphous area percentage in the structure. Here, it was found that on average 92% of the areas were amorphous.

EXAMPLE 2

[0108] An alloy formed from 70.6 percent by weight zirconium (Haines&Maassen Metallhandelsgesellschaft mbH Bonn, Zr-201 zirconium Crystalbar), 23.9 percent by weight copper (Alpha Aesar GmbH & Co KG Karlsruhe, Copper plate, Oxygen free, High Conductivity (OFCH) product number 45210), 3.7 percent by weight aluminium (Alpha Aesar GmbH & Co KG Karlsruhe, Aluminium Ingot 99,999% product number 10571) and 1.8 percent by weight niobium (Alpha Aesar GmbH & Co KG Karlsruhe, niobium film 99.97% product number 00238) was melted in an induction melting facility (VSG, inductively heated vacuum, melting and casting facility, Nrmont, Freiberg) under 800 mbar argon (Argon 6.0, Linde AG, Pullach) and poured into a water-cooled copper mould. A fine powder was produced from the alloy thus produced using a method as is known for example from WO 99/30858 A1 in a Nanoval atomizing apparatus (Nanoval GmbH & Co. KG, Berlin) by atomization of the melt with argon.

[0109] By separation by means of air classification using a Condux Ultra-Fine Classifier CFS (Netsch-Feinmahltechnik GmbH Selb Germany), the fine grain was separated, such that less than 0.1% of the particles were smaller than 5 m, i.e. at least 99.9% of the particles had a cross section or a dimensioning of 5 m or more, and all powder particles larger than 125 m were removed by screening by means of an analysis screen with 125 m mesh width (Retsch GmbH, Haan-Germany, product number 60.131.000125). The powder thus produced was examined by means of X-ray diffractometry and had an amorphous content of greater than 95%.

[0110] The powder thus produced was applied in layers in an EBM (electron beam melting) manufacturing facility (Arcam AB A1, Mndal, Sweden) without prior heating of the powder, wherein an electron beam with a power from 150 W to 210 W scanned the contour of the component and melted the powder particles. The individual layers thus solidified so quickly that crystallisation was suppressed and the alloy solidified amorphously. For the sintering of the powder in the volume of the component, the electron beam was fanned out to 50 beams and directed in a planar manner over the powder bed. The energy was thus low enough that the individual powder particles did not melt, but adhered only to their closest neighbour. The temperature of the powder bed must be kept below the crystallisation temperature T.sub.K of the alloy during the entire process.

[0111] The components produced as described were then compacted by pressing at a pressure of 200 megapascal (200 MPa) at a temperature of 400 C. for 180 seconds. The powder in the volume of the component was thus also completely compacted and forms a compact, pore-free body.

[0112] Ten components produced in this way were examined by means of metallographic microsection with regard to the amorphous area percentage in the structure. Here, it was found that on average 87% of the areas were amorphous .

[0113] The results measured for Examples 1 and 2 are presented in the following table in conjunction with a reference measurement:

TABLE-US-00001 Enthalpy of crystallisation Crystallinity Amorphicity J/g % % Reference 47.0 0 100 Example 1 34.0 8 92 Example 2 32.2 13 87

[0114] Test and Inspection Methods

1) Method for determining the particle size of metal alloy powders:

[0115] The particle size of inorganic powders was determined by laser light scattering using a Sympatec Helos BR/R3 (Sympatec GmbH), equipped with a RODOS/M dry disperser system with the vibratory feeding unit VIBRI (Sympatec GmbH). Sample volumes of at least 10 g were provided dry, dispersed at a primary pressure of 1 bar, and the measurement was started. An optical concentration of 1.9% to 2.1% was used as starting criterion. The measurement time was 10 seconds. The evaluation was performed in accordance with the MIE theory, and the d50 was used as a measure for the particle size.

2) Inspection method for determining the density:

[0116] To determine the density a geometrically exact cuboid was produced by grinding of the surfaces, such that this could be measured exactly using a digital outside micrometer (PR1367, Mitutoyo Messgerte Leonberg GmbH, Leonberg). The volume was then determined mathematically. The exact weight was then determined on an analytical balance (XPE analytical balance from Mettler-Toledo GmbH). The density was given by forming the ratio of weighed weight and calculated volume.

[0117] The theoretical density of an amorphous alloy corresponds to the density at the melting point.

3) Inspection method for determining the amorphous area percentage in the component:

[0118] For this purpose fifteen metallographic polished sections were produced in accordance with DIN EN ISO 1463 (as valid at date May 26, 2014), wherein polishing was performed using an SiC film 1200 (Struers GmbH, Willich) and by subsequent polishing steps using diamond polishing means with 6 m, 3 m and 1 m (Struers GmbH, Willich), and lastly with the chemo-mechanical oxide polishing suspensions OP-S (Struers GmbH, Willich). The polished surfaces thus produced were examined under a light microscope (Leica DM 4000 M, Leica DM 6000 M) with a magnification of 1000 for crystalline area percentages in the microsection. An evaluation of area percent crystalline proportion to total area of the polished section was made in this regard using the software Leica Phase Expert, wherein the dark regions were assessed as crystalline and the light regions were assessed as amorphous. The amorphous matrix was for this purpose defined as reference phase and was expressed as percentage of the total measured area. 10 different sample areas were measured and averaged.

4) Inspection method for determining the conversion temperatures:

[0119] A Netzsch DSC 404 F1 Pegasus calorimeter (Erich NETZSCH GmbH & Co. Holding KG) equipped with a high-temperature tube furnace with Rh meander heater, an integrated control thermocouple type S, DSC404F1A72 sample carrier system, crucible made of Al.sub.2O.sub.3 with cover, an OTS system for removing traces of oxygen during the measurement including three getter rings and an evacuation system for automatic operation with two-stage rotary pump was used here. All measurements were taken under inert gas (Argon 6.0, Linde AG) with a throughflow rate of 50 ml/min. The evaluation was performed using the software Proteus 6.1. To determine the TT, the tangent method (glass transition) was used in the range between 380 C. and 420 C. (Onset, Mid, Inflection, End). In order to determine the TK, the complex peak evaluation was used in the temperature range 450-500 C. (Area, Peak, Onset, End, Width, Height), and for Tm the complex peak evaluation was used in the temperature range 875-930 C. (Area, Peak, Onset, End, Width, Height). In order to take the measurement, 25 mg+/0.5 mg sample were weighed into the crucible, and the measurement was taken at the following heating rates and temperature ranges.

20-375 C.: heating rate 20 K/min
375-500 C.: heating rate 1 K/min
500-850 C.: heating rate 20 K/min
above 850 C.: heating rate 10 K/min

[0120] In order to determine the amorphous content of the component the enthalpy of crystallisation was determined using the complex peak method, wherein a 100% amorphous sample (obtained by atomizing) with an enthalpy of crystallisation of 47.0 J/g was used as reference.

[0121] The quotient of enthalpy of crystallisation of the component to enthalpy of crystallisation of the reference gives the percentage of the amorphous phase.

5) Determination of the elementary composition by means of emission spectrometry analysis (ICP):

[0122] An emission spectrometer Varian Vista-MPX (from the company Varian Inc.) was used. In each case two calibration samples were produced and measured for the metals from standard solutions with known metal content (for example 1000 mg/l) in aqua regia matrix (concentrated hydrochloric acid and concentrated nitric acid, in the ratio 3:1).

[0123] The parameters of the ICP device were:

power: 1.25 kW
plasma gas: 15.0 l/min (Argon)
auxiliary gas: 1.50 l/min (Argon)
atomizer gas pressure: 220 kPa (Argon)
repetition: 20 s
stabilisation time: 45 s
observation height: 10 mm
sample aspiration: 45 s
flushing time: 10 s
pump speed: 20 rpm
repetitions: 3

[0124] To measure a sample: 0.10 g+/0.02 g of the sample were mixed with 3 ml of nitric acid and 9 ml of hydrochloric acid, as specified above, and digested in a microwave (Anton Paar, apparatus: Multiwave 3000) at 800-1200 W for 60 min. The enclosed sample was transferred with 50 vol. % hydrochloric acid into a 100 ml flask and measured.

[0125] The features of the invention disclosed in the above description, the figures and also in the claims, the flow diagram and the practical examples may be essential individually and also in any combination for the implementation of the invention in the various embodiments thereof.