A method of improving the density of a platinum-based powder metallurgy alloy

Abstract

The application relates to a method for improving the density of a platinum-based powder metallurgy alloy, which realizes the purpose of reducing the porosity of a precious metal powder metallurgy alloy ingot and improving the material density through vacuum melting, powder preparation, resonance compaction, liquid phase sintering, controlled forging and other processes. The above process is adopted, the high-temperature endurance strength and toughness of the platinum-based powder metallurgy alloy are greatly improved, the high-temperature service life of the product is significantly enhanced, and good economic benefits are brought.

Description

Technical Field

[0001] This invention relates to a method for improving the density of platinum-based powder metallurgy alloys, specifically relating to the field of metal material smelting technology. Background Technology

[0002] Platinum-based alloys are widely used in the high-end glass manufacturing industry, operating in extremely harsh environments. They must withstand prolonged exposure to high-temperature glass molten metal (1200–1650℃), corrosion, and thermal shock, leading to severe creep and fatigue. In recent years, the industry has innovated and introduced new technologies to improve the high-temperature mechanical properties, corrosion resistance, and oxidation resistance of platinum-based alloys. Powder metallurgy technology is one such highly effective method. Currently, using the principle of dispersion strengthening, powder metallurgy technology can increase the high-temperature strength of platinum-based alloys by more than 150% and improve creep resistance by more than 300%.

[0003] However, platinum-based powder metallurgy alloys prepared by commonly used powder metallurgy methods such as atomization and electrical discharge machining still have certain deficiencies in density, which can lead to significant potential problems in their use. Currently, the highest density of platinum-based powder metallurgy alloys prepared by different processes is 99.76%, which inevitably results in the presence of a certain number of pores or voids in the product. Under prolonged use at high temperatures, these pores or voids will expand, accumulate, and extend, eventually leading to cracking or even complete fracture. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned shortcomings and provide a method for improving the density of platinum-based powder metallurgy alloys. This method involves processes such as vacuum melting, powder preparation, resonant compaction, liquid-phase sintering, and controlled forging to ultimately produce platinum-based powder metallurgy alloy materials of different sizes. Furthermore, this invention also provides alloy products or alloy materials prepared by the aforementioned method for improving the density of platinum-based powder metallurgy alloys.

[0005] The basic principles and advantages of this invention are as follows:

[0006] (1) A plasma rotating electrode powder-making device is used to produce micron-sized platinum-based alloy powder with uniform particle size, high sphericity, and direct drying through high rotation speed. At the same time, the oxygen partial pressure is adjusted to allow the powder to be oxidized simultaneously during the preparation process. This method greatly shortens the drying and oxidation time, and the obtained powder can be directly used in the next step.

[0007] (2) Through the acoustic-magnetic coupling field, macroscopic and microscopic vibration flow occur simultaneously inside the powder, so as to achieve the purpose of powder self-filling and redispersing, and obtain neatly arranged and densely combined pellets to be sintered.

[0008] (3) Innovative liquid phase sintering technology was used. Vacuum degassing was first performed in a vacuum high-temperature furnace. After the vacuum degree reached below 0.03 Pa, pressure molding and near-melting point liquid phase sintering were continuously achieved to obtain a preliminary finished ingot with extremely high density.

[0009] (4) After repeated verification, a set of process schemes were obtained to further improve the density of the above finished ingots and reduce internal defects by using free forging.

[0010] Specifically, the technical solution adopted in this invention is as follows:

[0011] A method for improving the density of platinum-based powder metallurgy alloys includes the following steps:

[0012] 1.1 Vacuum melting: Platinum and alloying elements are prepared and placed in a vacuum induction furnace for melting. The melting crucible is a zirconia crucible. After melting, the alloy ingot is cast into a special mold.

[0013] 1.2 Powder preparation: The ingot obtained above is placed in a plasma rotary powder making equipment to obtain platinum-based alloy powder of the required particle size and achieve simultaneous oxidation;

[0014] 1.3 Resonance compaction: After obtaining the platinum-based alloy powder, large particles of residue are removed by screening. The remaining powder with uniform particle size is weighed to an appropriate weight and placed into a high-frequency resonance device for compaction.

[0015] 1.4 Liquid phase sintering: The compacted powder, together with the mold, enters a vacuum high-temperature furnace and undergoes a process of pressure molding, vacuum degassing, and liquid phase sintering to obtain the finished ingot;

[0016] 1.5 Controlled forging: The finished ingot obtained in step 1.4 is subjected to multiple free forgings through controlled forging to obtain a billet of a certain thickness. The billet is then processed into various products such as plates, sheets, bars, and wires through conventional processing methods.

[0017] Preferably, the alloying element mentioned in step 1.1 is selected from one or more of Rh, Au, Al, Zr, Y, Sc, Pd, etc.

[0018] Furthermore, the melting temperature in step 1.1 is 1800–2000℃, the melting time is 20–30 min, the venting time is 20–30 min, and the refining time is 5–10 min, to obtain liquid metal before casting.

[0019] Preferably, the plasma rotary powder-making equipment described in step 1.2 has a rotation speed of 10,000 to 60,000 r / min, a particle size of 20 to 100 μm, and an oxygen partial pressure of 1 to 6 × 10⁴ Pa.

[0020] Preferably, the resonant frequency in step 1.3 is 1000-5000Hz and the weight is 3-10kg.

[0021] Preferably, the vacuum degree of the vacuum degassing process in step 1.4 is ≤0.03Pa, and the liquid phase sintering temperature is 1700~1800℃.

[0022] Preferably, in the multi-pass free forging process described in step 1.5, the initial forging temperature is 1400-1500℃, the final forging temperature is 1100-1200℃, and the processing amount per forging pass is from 5-10% to 10-15%, and finally 5-10%, and the free forging of each pass is carried out according to this pattern.

[0023] On the other hand, the present invention provides alloy products prepared by any of the above methods.

[0024] The beneficial effects achieved by this invention compared with the prior art are as follows:

[0025] Traditional platinum-based powder metallurgy alloy processes cannot achieve optimal density. Whether using atomization or electrical discharge machining (EDM), performance tests on the final products reveal that after prolonged high-temperature loading and eventual fracture, fracture analysis shows insufficient internal density. Under prolonged high-temperature loading, pores and voids grow and connect, forming numerous creep cavities and even central voids. This invention, however, utilizes a series of innovative processes to increase the maximum density of platinum-based powder metallurgy alloys from 99.76% to 99.93%, resulting in a significant improvement in high-temperature performance. The high-temperature creep fracture surface shows a uniform microstructure with almost no obvious creep cavities.

[0026] The technical solution provided by this invention can be applied not only to the production of platinum-based materials, but also to other metals or alloys such as gold, silver, iridium, and rhodium. It has promising applications. Attached Figure Description

[0027] Figure 1 High-temperature load fracture surface diagram of alloy products produced by traditional atomization process.

[0028] Figure 2 This is a high-temperature load fracture surface diagram of an alloy product manufactured using the traditional electrical discharge machining (EDM) process.

[0029] Figure 3 This is a high-temperature load fracture surface diagram of the alloy product prepared in Example 1 of the present invention. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] Example 1:

[0032] 1.1 Vacuum melting: 10 kg of platinum ingots meeting the SM / Pt-99.95% standard, 530 g of rhodium powder meeting the SM / Rh-99.95% standard, and 62 g of zirconium rods with a purity of 99.9% were placed into a vacuum induction furnace for melting. The melting crucible was a zirconium oxide crucible. The melting time was 25 min, the venting time was 30 min, and the refining time was 5 min. The alloy ingots were then cast into a special mold.

[0033] 1.2 Powder Preparation: The ingot obtained above was placed in a plasma rotary powder generator, with the rotation speed set to 25000 r / min, the feed rate to 2.2 cm / s, and the oxygen partial pressure to 3 × 10⁻⁶. 4 Pa, the final platinum-based alloy powder with a particle size of D was obtained. 90 =75μm;

[0034] 1.3 Resonance tapping: After obtaining platinum-based alloy powder, large particles of residue are removed by screening, leaving powder with uniform particle size (D). 90 Weigh 6 kg of material (<60μm) and place it in a high-frequency resonance device. Set the resonance frequency to 3000Hz and the time to 2min, and then vibrate it to compact the material.

[0035] 1.4 Liquid Phase Sintering: The compacted powder, along with the mold, is placed into a vacuum high-temperature furnace. After evacuating to a vacuum degree ≤0.03 Pa, the temperature is raised to 1500℃, and then 2×10⁻⁶ molten metal is added. 5 P oxygen, and continue to heat to 1760℃, hold for 30 minutes to obtain the finished ingot;

[0036] 1.5 Controlled forging: The finished ingot obtained in step 1.4 is subjected to free forging with an initial thickness of 50mm and an initial forging temperature of 1500℃. During the first forging pass, the ingot is first pounded on all six sides with a small deformation of 5%, then pounded on all six sides with a large deformation of 10%, and finally upset or stretched with a small deformation of 5% before the temperature drops to 1100℃. The above operations are repeated until the billet reaches the target thickness.

[0037] The blanks obtained in step 1.5 are processed into various products such as plates, sheets, rods, and wires using conventional processing methods, and then relevant tests are conducted.

[0038] Examples 2-6 changed the types, contents and some parameters of alloying elements, while the remaining steps were basically the same as in Example 1. The specific changes and test results are shown in Table 1 below.

[0039] Table 1 Examples 1-6 and Comparative Examples

[0040] Element Powder particle size Resonance frequency Sintering temperature Density Creep time Atomization method <![CDATA[PtRh5Zr 0.4 ]]> Around 100μm / 1300℃ 99.68％ ＜5h Electrical Discharge Machining <![CDATA[PtRh5Zr 0.4 ]]> 0.5~20μm / 1300℃ 99.76％ ＜20h Example 1 <![CDATA[PtRh5Zr 0.4 ]]> 60μm 3000Hz 1760℃ 99.93％ ＜48h Example 2 <![CDATA[PtZr 0.4 ]]> 60μm 2500Hz 1710℃ 99.90％ ＜30h Example 3 <![CDATA[PtAu5Zr 0.7 ]]> 60μm 1500Hz 1700℃ 99.85％ ＜37h Example 4 <![CDATA[PtY5Zr 0.4 ]]> 60μm 2500Hz 1710℃ 99.86％ ＜33h Example 5 <![CDATA[PtRh5Zr 0.4 ]]> 50μm 3000Hz 1750℃ 99.92％ ＜46h Example 6 <![CDATA[PtRh5Zr 0.4 ]]> 70μm 3000Hz 1770℃ 99.89％ ＜40h

[0041] Note: 1. Density is calculated as actual density / theoretical density. The theoretical density is calculated after detecting the alloy composition by ICP.

[0042] 2. The creep test conditions are 1400℃ and 500g load.

[0043] As shown in Table 1 above, compared with traditional platinum-based powder metallurgy alloy processes, this invention can increase the maximum density of platinum-based powder metallurgy alloys from 99.76% to 99.93% through a series of innovative processes. Traditional preparation methods cannot achieve the optimal density. Whether it is the atomization method or the electrical discharge machining method, performance tests on the final products show that after the material is subjected to long-term load at high temperature until fracture, fracture analysis shows that due to insufficient internal density, pores and voids grow and connect during long-term high-temperature loading, as shown in the attached table. Figure 1 and 2 The diagram shows numerous creep cavities, even central voids. However, the platinum-based powder metallurgy alloy prepared by the method described in this invention exhibits significantly improved high-temperature performance due to the increased maximum density, as shown in the attached diagram of its high-temperature creep fracture surface. Figure 3 As shown, the tissue is evenly distributed with almost no obvious creep cavities. The comparison of the above results indicates that the present invention has achieved good technical effects.

[0044] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for improving the density of platinum-based powder metallurgy alloys, characterized in that, Includes the following steps: 1.1 Vacuum melting: Platinum and alloying elements are prepared and placed in a vacuum induction furnace for melting. The melting crucible is a zirconia crucible. After melting, the alloy ingot is cast into a special mold. 1.2 Powder Preparation: The ingot obtained above is placed in a plasma rotary powder-making device to obtain platinum-based alloy powder of the required particle size and achieve simultaneous oxidation; wherein, the rotation speed of the plasma rotary powder-making device is 10000~60000 r / min, the particle size is 20~100 μm, and the oxygen partial pressure is 1~6×10 4 Pa; 1.3 Resonance compaction: After obtaining the platinum-based alloy powder, large particles of residue are removed by screening. The remaining powder with uniform particle size is weighed to an appropriate weight and placed in a high-frequency resonance device for compaction; wherein, the resonance frequency is 1000~5000Hz and the weight is 3~10kg. 1.4 Liquid phase sintering: The compacted powder, together with the mold, enters a vacuum high-temperature furnace and undergoes a process of pressure molding, vacuum degassing, and liquid phase sintering to obtain a finished ingot; wherein, the vacuum degree during the vacuum degassing process is ≤0.03Pa, and the liquid phase sintering temperature is 1700~1800℃. 1.5 Controlled Forging: The finished ingot obtained in step 1.4 is subjected to multiple passes of free forging through controlled forging to obtain a billet. The billet is then processed into various plates, sheets, bars, and wires using conventional processing methods. In the multiple passes of free forging, the initial forging temperature is 1400~1500℃, the final forging temperature is 1100~1200℃, and the processing amount per pass is from 5~10%, to 10~15%, and finally 5~10%. Each pass of free forging is carried out according to this pattern.

2. The method for improving the density of platinum-based powder metallurgy alloys according to claim 1, characterized in that: The alloying elements mentioned in step 1.1 are selected from one or more of Rh, Au, Al, Zr, Y, Sc, and Pd.

3. The method for improving the density of platinum-based powder metallurgy alloys according to claim 1, characterized in that: The melting temperature in step 1.1 is 1800~2000℃, the melting time is 20~30min, the venting time is 20~30min, and the refining time is 5~10min, to obtain liquid metal before casting.

4. The method for improving the density of platinum-based powder metallurgy alloys according to claim 1, characterized in that: The platinum and alloying elements prepared in step 1.1 are platinum ingots that meet the SM / Pt-99.95% standard, rhodium powder that meets the SM / Rh-99.95% standard, and zirconium rods with a purity of 99.9%.

5. The alloy product prepared by the method according to any one of claims 1-4.

6. The alloy product according to claim 5, characterized in that: The maximum density of the alloy product is increased to 99.93%, and the creep time is extended to <48h.

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